A revision of the lithostratigraphic units of the Coastal Plain of Georgia : the Oligocene

A Revision of the Lithostratigraphic Units of the Coastal Plain of Georgia
THE OLIGOCENE
Paul F. Huddleston
DEPARTMENT OF NATURAL RESOURCES ENVIRONMENTAL PROTECTION DIVISION
GEORGIA GEOLOGIC SURVEY
I
BULLETIN 105

Cover photo: Seventy feet of Bridgeboro Limestone exposed at the the type locality in the southern-most pit of the Bridgeboro Lime and Stone Company, 6.5 miles west-southwest of the community of Bridgeboro, south of Georgia 112, Mitchell County.

A Revision of the Lithostratigraphic Units of the Coastal Plain of Georgia THE OLIGOCENE
Paul F. Huddlestun
Georgia Department of Natural Resources Joe D. Tanner, Commissioner
Environmental Protection Division Harold F. Reheis, Director Georgia Geologic Survey
William H. McLemore, State Geologist
Atlanta 1993
BULLETIN 105

TABLE OF CONTENTS
Page
LIST OF ILLUSTRATIONS ............................................................................................................................................... v ABSTRACT ........................................................................................................................................................................ 1 ACKN"OWLEIJGMENTS ................................................................................................................................................. 1 INTRODUCTION ..............................................................................................................................:.............................. 2
Methods ...........................................,.................................................................................................................... 2 Oligocene Correlation Problems ....................................................................................................................... 12 LITHOSTRATIGRAPHY ................................................................................................................................................... 15 Eastern Gulf of Mexico Stratigraphic Association ......................................................................................... 15
Vicksburg Group .................................................................................................................................... 15 Marianna Limestone .............................................................................................................. 16 Glendon Limestone ............................................................................................................... 20
Shellstone Creek beds ............................................................................................................................. 21 Undifferentiated residuum .................................................................................................................. 25 Gulf Trough Stratigraphic Association ............................................................................................................ 28 C>chlockonee Formation ....................................................................................................................... 28
Pridgen Limestone Member ................................................................................................. 35 Wolf Pit Dolostone ...........................................................................~.....................................................41 Okapilco Limestone ..............................................................................................................................44 Bridgeboro Limestone .......................................................................................................................... 46
Florala Limestone Member ................................................................................................... 55 Florida Bank Stratigraphic Association ........................................................................................................... 61
Ellaville Limestone ................................................................................................................................ 61 Suwannacoochee Dolostone ..............................................~................................................................. 67 Suwannee Limestone ............................................................................................................................ 70 Atlantic Continental Shelf Stratigraphic Association ............................................................................................................................................. 77
Lazaretto Creek Formation ................................................................................................... 77 Cooper Formation .........................:........................................................................................ 82 Stratigraphic Association of Uncertain Affinities ............................................................................................................................. 86 Undifferentiated calcareous sand and
sandy limestone ...................................................................................................... 86 DISCUSSION ..................................................................................................................................................................... 88
Primary Structural Elements ............................................................................................................................ 88 Florida Platform ........................................................................~...........................................................88 South Georgia rift ..................................................................................................................................88 Piedmont Slope ......................................................................................................................................91 Peninsular Arch ..................................................................................................................................... 91
Constructional features of sedimentary origin ...............................................:.............................................. 94 Georgia Channel System ......................................................................................................................94 Southeast Georgia Embayment ........................................................................................................... 98 Beaufort Arch ..................................,......................................................................................................98 C>cala Arch ............................................................................................................................................ 100
Hypothetical Structure .....................................................................................................................................100 Chattahoochee Arch ........................................................................................................................... 100 Barwick Arch ....................................................................................................................................... 101
iii

TABLE OF CONTENTS (CONT.)
Page
Faults .................................................................................................................................................................. 102 Paleogeographic Elements ........................................................................................................................................... 103
Florida Bank ....................................................................................................................................................... 103 Suwannee Strait ............................................................................................................................................... 106 Atlantic Continental Shelf .............................................................................................................................. 110 Suwannee Current .......................................................................................................................................................... 110 Oligocene Faunal Provinces ........................................................................................................,................................. 112 Eocene/Oligocene Boundary ........................................................................................................................................ 116 Correlation of Oligocene Stratigraphic Units, Sequence Stratigraphy, and Paleogeography Across Georgia and Northern Florida .......................................................................................................... 116
Introduction ........................................................................................................................................ 116 Depositional History ......................................................................................................................... 119
Bumpnose-Red Bluff-Forest Hill depositional sequence .......................................................................................... 120
Post-Bumpnose-Red Bluff hiatus ..................................................................................... 122 Ellaville-Glendon-Marianna-
Mint Spring depositional sequence ................................................................... 126 Suwannacoochee low stand of the sea ...........................................................................128 Suwannee-Byram depositional sequence ........................................................................ 129 Wolf Pit low stand of the sea ............................................................................................ 133 Okapilco-Bucatunna depositional sequence .................................................................. 133 Post-Vicksburgian-pre-Chickasawhayan
low stand of the sea ........................................................................,..................... 135 Chickasawhayan depositional event .............................................................................. 138 Post Chickasawhayan- pre-Miocene
low stand(s) of the sea .......................................................................................... 140 Environmental Evolution during the
Oligocene ........................................................................................................................................................... 143 Miocene/Oligocene Boundary ..................................................................................................................................... 143 References Cited .........;.................................................................................................................................................... 144
iv

LIST OF ILLUSTRATIONS

Figures

Page

1. Location map of the Study area ...................................~......................................................................................3

2. Location map of type localities, reference localities, core sites, and well sites in Georgia and on the continental shelf of Georgia ...............................................................5

3. Location map of type localities, reference localities, and core sites in the lower Savannah River area of Georgia and coastal South Carolina ...................................................................................................................................................... 7

4. Location map of type localities, reference localities, core sites, and well sites in peninsular Florida.......................................................................................................................... 9

5. Location map of type localites, reference localities, and core sites in northwestern Florida and Alabama ................................................................................................................. 11

6. The type locality of the Marianna Limestone ....................................................................,......~..................... 17

7. The areal distribution (outcrop and subcrop) of the Marianna Limestone in Georgia and northern Florida ......................................................................................................................19

8. The known distribution of the Glendon Limestone in Georgia ...................................:............................... 22

9. Reference locations for the Shellstone Creek beds ........................................................................................ 24

10. The areal distribution of undifferentiated Oligocene residuum in Georgia ............................................... 27

11. The type localities of the Ochlockonee Formation, Wolf Pit Dolostone, and Okapilco Limestone ............................................................................................................................................ 30

12. Lithology symbols ................................................................................................................................................ 31

13. The measured holostratotype of the Ochlockonee Formation ...................................................................... 32

14. The areal distribution (subcrop) of the Ochlockonee Formation in Georgia and northern Florida ......................................................................................................................................... 34

15. The type locality of the Pridgen Limestone Member of the Ochlockonee Formation, reference localities of the Okapilco Limestone and Wolf Pit . Dolostone, and locations of oil test wells of the Pridgen Prospect of Applin (1960) ..........................................................................................:............................................................ 36

16. The measured holostratotype of the Pridgen Limestone Member of the Ochlockonee Formation and parastratotype of the Wolf Pit Dolostone .................................................... 38

17. The areal distribution (subcrop) of the Pridgen Limestone Member of the Ochlockonee Formation in Georgia ..........................................................:......................................................39

18. The areal distribution (subcrop) of the Wolf Pit Dolostone ..........................................................................43

19. The measured holostratotype of the Okapilco Limestone and the Wolf Pit Dolostone ................................................................................,......................................................45

v

LIST OF ILLUSTRATIONS (CONT.)

Figures

Page

20. The areal distribution (subcrop) of the Okapilco Limestone ......................................................................47

21. The type locality of the Bridgeboro Limestone .............................................................................................49

22. The measured holostratotype of the Bridgeboro Limestone ....................................................................... 50

23. The areal distribution (outcrop and subcrop) of the Bridgeboro Limestone in Georgia ........................................................................................................................................................... 52

24. The type locality of the Florala Limestone Member of the Bridgeboro Limestone ..........................................................................................................................................,.................56

25. The measured holostratotype of the Florala Limestone Member of the Bridgeboro Limestone ..,....................................................................................................................................57

26. The areal distribution (outcrop and subcrop) of the Florala Limestone Member of the Bridgeboro Limestone in Georgia ........................................................................................59

27. The type localities of the Ellaville Limestone and Suwannacoochee Dolostone, and the reference locality of the Suwannee Limestone ............................................................62

28. Composite stratigraphic section along the Suwannee River from Dowling Park to the confluence with the Alapaha River compared with the Florida Geological Survey core Ellaville 1 (W-10657) ............................................................................ 63

29. The areal distribution (outcrop and subcrop) of the Ellaville Limestone in Georgia and northern Florida .......................................................................................................................... 65

30. The areal distribution (outcrop and subcrop) of the Suwannacoochee Dolostone in Georgia and northern Florida .....................................................,............................................ 69

31. The measured lectostratotype of the Suwannee Limestone ........................................................................ 73

32. The areal distribution (outcrop and subcrop) of the Suwannee Limestone in Georgia and northern Florida ..................................................................................................................... 75

33. The type locality of the Lazaretto Creek Formation in Georgia .................................................................. 79

34. The measured holostratotype of the Lazaretto Creek Formation .............................................................80

35. The areal distribution (subcrop) of the Lazaretto Creek Formation in Georgia ...................................... 81

36. The areal distribution (subcrop) of the Cooper Formation beneath the continental shelf of Georgia ......................................................................';.....................................,................85

37. The areal distribution of the undifferentiated calcareous sand and sandy limestone .................................................................................................................................................87

38. Proposed shallow structural elements controlled by basement structure in the Coastal Plain of Georgia and northern Florida ............................................................................................. 89

vi

Figures

LIST OF ILLUSTRATIONS (CONT.) Page

39. The South Georgia Rift from Daniel and others (1988) ................................................................................. 90

40. The Peninsular Arch and related features in Georgia and Florida .............................................................92

41. Stratigraphic cross-section across the Peninsular Arch from Dougherty County to Emanual County ........~......:..............................................................................................................93

42. Constructural features of sedimentary origin .................................................................;..............................95

43. Reconstruction of the Suwannee Channel, Tallahassee Embayment, and Southeast Georgia Embayment in Georgia and northern Florida ............................................................... 96

44. Reconstruction of the Gulf Troughand Chattahoochee Embayment in Georgia and northern Florida ..........................-.................................................................................................97

45. Early Oligocene paleogeographic elements of Georgia and northern Florida .................................................................................................:.........................................99

46. Schematic north-south cross-section illustrating the sequential northward migration of the Florida Bank and the subsequent termination of the bank .................................................................................................................................... 104

47. Late Eocene paleogeographic reconstructionof the Coastal Plain of Georgia and northern Florida ......................................................~...........................................................~.........;........;.......... 105

48. Latest Oligocene paleogeographic reconstruction of the Coastal Plain of Georgia and_northern Florida ......................................................................................................................... 107

49. Proposed paleogeography and paleoceanographic current distribution of the Florida and Suwannee Straits during the Midwayan ........................................................................... 108

50. Proposed paleogeography and paleoceanographic current system of the Florida artd Suwannee Straits region during the Sabinian high stands of the sea ............................................................................................................................................................ 109

51. Proposed paleogeography and paleoceanographic current distribution of the Florida and Suwannee Straits region during the late Jacksonian ........................................,...........:.. 111

52. Hypothetical cross-section of the Suwannee Current in the Gulf Trough Oligocene high stands and low stands of the sea ........................................................................................ 113

53. Distribution of Oligocene faunas in the Coastal Plain of Georgia and northern Florida during the deposition of the Suwannee Limestone ..................................................;... 114

54. Paleogeographic reconstruction of Georgia and northern Florida during the ten:llinal Eocene low stand of the sea ..................................................................................................... 118

55. Paleogeographic reconstruction of Georgia and northern Florida during the Bumpnose-Red Bluff-Forest Hill depositional sequence ............................................................................ 121

vii

LIST OF ILLUSTRATIONS (CONT.)

Figure

Page

56a. Model of sequential diminishing and termination of the Suwannee Current in the Gulf Trough from the latest Eocene through the Oligocene ...,..................................................... 123
56b. Model of sequential diminishing and termination of the Suwannee Current in the Gulf Trough from the lastest Eocene through the Oligocene ........................................................124
57. Paleogeographic reconstruction of Georgia and northern Florida during the post-Bumpnose-Red Bluff hiatus ............................................................................................... 125
58. Paleogeographic reconstruction of Georgia and northern Florida during the Ellaville-Glendon-Marianna-Mint Spring depositional sequence ..................................................... 127
59. Paleogeographic reconstruction of Georgia and northern Florida during the Suwannacoochee low stand of the sea ..............................................................._.......................................... 130
60. Paleogeographic reconstruction of Georgia and northern Florida during the Suwannee-Byram depositional sequence ..................................................................................................... 131
61. Paleogeographic reconstruction of Georgia and northern Florida during the Wolf Pit low stand of the sea ........................................................................................................................ 134
62. Paleogeographic reconstruction of Georgia and northern Florida during the Okapilco-Bucatunna depositional sequence ......................................................................................... 136
63. The Oligocene geologic section exposed in the Florida Geological Survey core Mathis 1 (W-8102) ............................................................................................................................................ 137
64. Paleogeographic reconstruction of Georgia and northern Florida during the post-Vicksburgian-pre-Chickasawhayan low stand of the sea ................................................................ 139
65. Paleogeographic reconstruction of Georgia and northern Florida during the Chickasawhayan depositional sequence ...................................................................................................... 141

Viii

PLATES

1.

Correlation chart of Oligocene stratigraphic units of Georgia and the

southeastern United States ............................................................................................................................ Jacket

2.

Stratigraphic cross-section along the axis of the Gulf Trough from the

core Coffee 4 (GGS-3541) in northern Coffee County, Georgia, to the core

Alum Bluff 1 (W-6901) in Liberty County, Florida ..................................................................................... Jacket

3.

Stratigraphic cross-section from Dougherty County, Georgia, to Ellaville,

Hamilton County, Florida .............................................................................................................................. Jacket

4.

Stratigraphic cross-section near the Savannah River from Screven County,

Georgia, to the inner continental shelf .......................................................................................................... Jacket

5.

East-west stratigraphic cross-section from Duncan Church, Florida to

AMCOR 6002 on the outer continental shelf............................................................................................... Jacket

IX

ABSTRACT
Lithostratigraphic units are described in terms of their stratigraphic associations. These include an eastern Gulf of Mexico stratigraphic association, a Gulf Trough stratigraphic association, a Florida Bank stratigraphic association, and an Atlantic continental shelfstratigraphic association. The faunal provinces and the stratigraphic associations appear to be directly related.
Four previously named Oligocene formations are recognized in this study: the typical Suwannee Limestone is largelyrestricted to the Florida Bank stratigraphic association but also occurs north of the GulfTrough in the central Georgia Coastal Plain, the Cooper Formation is confined to the Atlantic continental shelf stratigraphic association, and the Marianna Limestone and Glendon Limestone of the Vicksburg Group are restricted to the eastern Gulf of Mexico continental shelf stratigraphic association. Of seven new formations, the Ochlockon~ Formation, WolfPit Dolostone, Okapilco Limestone, and Bridgeboro Limestone are confined to the Gulf Trough stratigraphic association; the Ellaville Limestone and Suwannacoochee Dolostone are confined to the Florida Bank stratigraphic association; and the Lazaretto Creek Formation is restricted to the Atlantic continental shelf stratigraphic association. Of two new members, the Pridgen Limestone Member of the Ochlockonee Formation is confined to the northeastern part of the Gulf Trough and the Florala Limestone Member of the Bridgeboro Limestone occurs in both the eastern Gulf of Mexico and along the northern flank of the Gulf Trough. The Shellstone Creek beds, an informal unit, and undifferentiated Oligocene residuum, in part the Flint River formation of Cooke (1935), are restricted to the eastern Gulf of Mexico stratigraphic association. An undifferentiated calcareous sand and sandy limestone formation occurs only within the northeastern part of the Gulf Trough and on the shelf to the northwest. Its stratigraphic association is uncertain.
Four primary structural elements, the Florida Platform, South Georgia rift, Piedmont Slope, and Peninsular Arch have influenced the stratigraphic framework of the entire Georgia Coastal Plain since the inception of deposition in the Coastal Plain Province. Other smaller scale features, formerly considered to be structurally controlled (the Ocala Arch, Beaufort Arch, and Southeast Georgia Embayment), are considered here to be structures originating from differential sedimentation patterns. It is concluded, on the other hand, that the Chattahoochee Arch and Barwick Arch do not exist and the names should be abandoned, and that there is no evidence for, and no real evidence has ever been presented for, various faults postulated to be associated with the Gulf Trough (and Chattahoochee Embayment). The section on Oligocene paleogeographic elements is di-

vided into discussions onthe Florida Bank,the Suwannee Strait, and the Atlantic continental shelf. The Oligocene history of the Suwannee Current is discussed in relationship to these features.
Three marine faunal provinces (or associations) are recognized in the Georgia area during the Oligocene: a Gulf of Mexico continental shelf faunal province characteristic ofthe region north and west of the Gulf Trough, a Florida province characteristic of and largely restricted to the Florida Bank, and an Atlantic continental shelf faunal province. The Gulf Trough through most of the Lower Oligocene separated the Gulf of Mexico province from the Florida province. The chronology and regional correlation of Oligocene depositional events, eustatic sea level events, the evolvingpaleogeography, and the paleoenvironmental evolution ofGeorgia and northern Florida are discussed.
ACKNOWLEDGMENTS
Stratigraphic work that culminated in this report was initiated in 1964. During the past 16 years, many geologists on the staff of the Georgia Geologic Survey have contributed to the results of this project. Mr. S.M. Pickering, Jr., former State Geologist of Georgia, encouraged and supported the early phases of the project. Dr. W.H. McLemore, State Geologist of Georgia, has continued in the encouragement and support of the project to its completion. I wish to express thanks to Mr. C.W. Henry, former State Geologistof Florida, and Dr. WalterSchmidt, the State Geologist of Florida, for sharing the resources of the Florida Geological Survey. Special thanks are extended to Mr. Gerald S. Grainger of Southern Services, Inc. for providing access to cores of Georgia Power Company, and to the United States Gypsum Company for donating twelve coresfrom Thomas, Brooks, and Colquitt Counties to the Georgia Geological Survey. Ms. Muriel E. Hunter of Tallahassee, Florida, has been of special assistance to me in her wealth of knowledge on the Oligocene limestones and faunas of Florida and the Southeast. Dr. Lucy E. Edwards of the U.S. Geological Survey, Reston, Virginia, has proVided biostratigraphic information on limestonesin the Gulf Trough. Dr. Burt Carter of Georgia Southwestern College has provided stimulating discussions on the Oligocene stratigraphy and paleontology of southwestern Georgia. Jonathon Bryan of Florida State University has also provided stimulating input on the paleontology of the Oligocene of this region.
I also wish to extend my deepest thanks and gratitude to Mr. M.P. Crowell, Mr. D.M. Cannon, and Mr. H.D. Baker, drillers for the Georgia Geologic Survey, whose efforts in coring have contributed greatly to the satisfactory conclusion of this project.

1

INTRODUCTION

METHODS

This report, concerning the Oligocene Series of the Coastal Plain of Georgia (Fig. 1), is a part of a succession of stratigraphic reevaluations of the Georgia Coastal Plainand follows thereportcoveringtheMiocene through Holocene (Huddlestun, 1988). The purposes of this report are (1) to describe, as well as the currentdata permits, the Oligocene lithostratigraphic units of Georgia, (2) to base the lithostratigraphic definitions on the modem codes of stratigraphic nomenclature (American Commission on Stratigraphic Nomenclature, 1961, 1970; International Subcommission on Stratigraphic Classification, 1976; North American Commission on Stratigraphic Nomenclature, 1983), (3) to relate these units to the known Oligocene lithostratigraphic and chronostratigraphic framework of the southeastern Coastal Plain, (4) to relate the described stratigraphic units to the paleogeographic features of the region, (5) to evaluate the various described or postulated structural elements of the region that would involve Oligocene strata,-(6) to describe the physical relationships of the postulated structural elements with the Oligocene stratigraphic framework, and (7) to describe the chronology of events (sequence stratigraphy) that resulted in the regional stratigraphic framework.
To this end, seventeen lithostratigraphic units are described. These include one group, eleven formally defined formations (seven new formations and four previously named formations), two new members, one informal unit, and two undifferentiated units. Of the stratigraphic namesapplied toOligocenestratigraphicunitsin Georgia prior to the 1970's, only the redefined Suwannee Limestone is still recognized as a valid formation. Oligocene formations that had been recognized in Georgia but which are no longer used include the Flint River formati9n of Cooke (1935), which has not been considered a valid lithostratigraphic unit for many years (MacNeil, 1947a,1947b);theByramFormationofMississippi whose extensionintoGeorgia wasnotlithostratigraphicallyvalid (Pickering, 1970); and the Vicksburg Formation ofVeatch and Stephenson (1911) which in Georgia is now recognized as both a group and a stage (the Vicksburg Group and Vicksburgian Stage).
In addition to the above lithostratigraphic units, various other geologic and paleophysiographic features that are involved in concepts of the Oligocene stratigraphic framework of Georgia are discussed and evaluated. These geologic and paleophysiographic features include the Gulf Trough and its relationship to the Chattahoochee Embayment, Apalachicola Embayment, Suwannee Channel, and Tallahassee Embayment; to the Suwannee Strait; to the Peninsular Arch; the Piedmont
Slope; Florida Platform; Florida Bank; Ocala Arch; Beau-
fort Arch; Southeast Georgia Embayment; and various faults.

The initial process of lithostratigraphic subdivision of the Oligocene section of Georgia and northern Florida was based on core examinations and descriptions. This effort did not stem from a systematic study of the Oligocene but resulted from logging and sampling of cores (for microfossil content) from Georgia, South Carolina, and Florida (Figs. 2-5) and as parts of different studies. Thirty four cores from the panhandle and northem Florida were examined, logged and sampled for foraminiferal content as part of a PhD dissertation (Huddlestun, 1984). Twenty nine cores were examined, logged, and sampled for foraminiferal content as a part of the study of the geologic section in the vicinity of the Savannah River in eastern Georgia (in part, Huddlestun, 1988). Twelve cores from Thomas, Brooks, and Colquitt Counties, Georgia., were examined and logged in an effort to understand the stratigraphic framework of the northwestern part of the Florida Platformin Georgia; five cores were logged and sampled for foraminiferal content for the Gulf Trough Project; and two cores were logged from the Suwannee River area in Florida to support field workalong the Suwannee River and Withlacoochee River in 1976 to precisely determine the lithology of the Suwannee Limestone. Other cores were logged and sampled for foraminiferal content where the Oligocene occurs as erosional outliers, as residuum, or is absent. Two cores were logged and sampled for foraminiferal content from the Hawkinsville area (Pulaski County, Georgia) in preparation for Guidebook 12 of the Southeastern Section of the Geological Society of America (Huddlestun and others, 1974); one core (AMCOR 6002) was taken by the U.S. Geological Survey on the outer continentalshelfofGeorgia(Hathawayandothers,1976); eight discontinuous cores were taken by the U. S. Army Core of Engineers on the outer continental shelf of Georgia, one core was logged and sampled for foraminiferal content from Wayne County, Georgia (Pickering, 1974); and seven cores were logged where the Oligocene is absent and the Miocene Hawthorne Group directly overlies the Upper Eocene Group in southeastern Georgia and eastern Florida. A number of cores from Port Royal Sound in the Beaufort County area of South Carolina were examined. One core, from near Coosawhatchie, South Carolina, also was logged and sampled. In all of these South Carolina cores, the Oligocene is absent. All totaled, this reevaluation of the Oligocene stratigraphy of Georgia and northern Florida is based on over hundred logged cores, many of which also were sampled for foraminifera.
A regional correlation chart (Pl. 1) of the Oligocene formations was constructed on the basis ofbiostratigraphic correlation and stratigraphic position. Standard procedures were employed in constructing the chart.

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Explanation of Symbols on Figure 2
TYPE LOCALITIES
A ... Ochlockonee Formation (upper part), Wolf Pit Dolostone, and Okapilco Limestone; Colquitt 5 (GGS-3199), ColquittCounty, Georgia.
B ... Ochlockonee Formation (lower part); Colquitt 9 (GG5-3535), Colquitt County, Georgia. C ... Pridgen Limestone Member of the Ochlockonee Formation; Coffee 4 (GGS-3541), Coffee County, Georgia. D ... Bridgeboro Limestone; Mitchell County, Georgia.

REFERENCE LOCALITIES a ... Pridgen Limestone Member of the Ochlockonee Formation and Okapilco Limestone; Berrien 10 (GG5-3542),
Berrien County, Georgia. b ... Ellaville Limestone and Suwannacoochee Dolostone; Thomas 4 (GG5-3188), Thomas County, Georgia. C ... Wolf Pit Dolostone, and Okapilco Limestone; Coffee 4, (GG5-3541), Coffee County, Georgia.

CORE SITES AND WELL SITES

A ... Colquitt 5 (GG5-3199); Colquitt County, Georgia

1 ... Colquitt 6 (GGS-3212); Colquitt County, Georgia

2 ... Colquitt 7 (GG5-3213) and Colquitt 10 (GG5-3544); Colquitt County, Georgia.

3 ... Colquitt 8 (GG5-3214); Colquitt County, Georgia.



B ... Colquitt 9 (GGS-3535); Colquitt County, Georgia.

4 ... Colquitt 10 (GG5-3196); Colquitt County, Georgia.

5 ... Colquitt 11 (GG5-3545); Colquitt County, Georgia.

b ... Thomas 4 (GG5-3188); Thomas County, Georgia.

6 ... Thomas 5 (GG5-3207); Thomas County, Georgia.

7 ... Thomas 6 (GG5-3215); Thomas County, Georgia.

8 ... Brooks 7 (GG5-3189) and Brooks 9 (GG5-3209); Brooks County, Georgia.

9 ... Brooks 8 (GG5-3208); Brooks County, Georgia.

10 ... Brooks 10 (GG5-3211); Brooks County, Georgia.

a ... Berrien 10 (GG5-3542); Berrien County, Georgia.

C ...Coffee 4 (GG5-3541); Coffee County, Georgia.

11 ... Well Cuttings, GG5-468, GG5-508, GGS-509 Coffee County, Georgia.

. 12 ... Pulaski 3 (GG5-3111); Pulaski County, Georgia.

13 ... Pulaski 4 (GG5-3112); Pulaski County, Georgia.

14 ... Pulaski 5 (GG5-3511); (Arrowhead core); Pulaski County, Georgia.

15 ... Laurens 1 (GG5-3523); (Laurens County core); Laurens County, Georgia.

16 ... U.S. Geological Survey test wellS (GGS-1063); Glynn County, Georgia.

17 ... AMCOR 6002; continental shelf.

18 ... TACTS core A; continental shelf

19 ... TACTS core B; continental shelf

20 ... TACTS core C; continental shelf

21 ... TACTS coreD; continental shelf

22 ... TACTS core F; continental shelf

23 ... Wayne 2 (GG5-3512); Wayne County, Georgia.

24 ... Cll:mberland Island 1 (GG5-3426); Camden County, Georgia

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Figure 2. Location map of type localities, refererence localities, core sites, and well sites in Georgia and on the continental shelf of Georgia.
5

Explanation of Symbols on Figure 3
TYPE LOCALITY E... Lazaretto Creek Formation; Chatham 11 (GG5-1393), Chatham County, Georgia.
REFERENCE LOCALffiES c ... Suwannee Limestone; Blue Springs, Screven County, Georgia. d ... Lazaretto Creek Formation; Petit Chou 1 (GG5-1164), Petit Chou Island, Chatham County, Georgia.
CORE SITES AND WELL SITES d ... Petit Chou 1 (GG5-1164); Chatham County, Georgia. 25 ... Screven 1 (GG5-1170); Screven County, Georgia. 26 ... Screven 8 (GG5-3198); Screven County, Georgia. 27... Georgia Power Company cores B3**, B21**, B22**; 28 ... Georgia Power Company core B38**, Screven County, Georgia. 29 ... Effingham 3 (GG5-2175); Effingham County, Georgia. 30 ... Effingham 6 (GG5-2179); Georgia Power Company core B40**; Effingham County, Georgia. 31 ... Effingham 9 (GG5-3107); Effingham 11 (GG5-3109); Effingham County, Georgia. 32 ... Effingham 10 (GG5-3108); Effingham County, Georgia. 33 ... Effingham 12 (GG5-3110); Effingham County, Georgia. 34 ... Effingham 13 (GG5-3140); Effingham County, Georgia. 35 ... Effingham 14 (GG5-3155); Effingham County, Georgia. 36 ... Georgia Power Company core B41**; Effingham County, Georgia. 37 ... Chatham 1 (GG5-1164); Chatham County, Georgia. 38 ... Chatham 3 (GG5-1341); Chatham County, Georgia. 39 ... Chatham 10 (GG5-1394); Chatham County, Georgia. E ... Chatham 11 (GG5-1393); Chatham County, Georgia. 40 ... Chatham 12 (GG5-1411); Chatham County, Georgia. 41 ... Chatham 13 (GG5-1445); Chatham County, Georgia. 42 ... Chatham 14 (GG5-3139); Chatham County, Georgia. 43 ... Chatham 15 (GG5-3138); Chatham County, Georgia. 44 ... Chatham 17 (GG5-3554); Chatham County, Georgia. 45 ... Chatham 18 (GG5-3639); Chatham County, Georgia. 46 ... Chatham 19 (GG5-3640); Chatham County, Georgia. 47 ... Dawsons Landing; Jasper County, South Carolina. 48 . . Port Royal Sound; Beaufort County, South Carolina.
**Cores are no longer available
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Figure 3. Location map of reference localities and core sites in the lower Savannah River area of Georgia and coastal South Carolina.
7

Explanation of Symbols on Figure 4 TYPE LOCALITY
F ... Ellaville Limestone and Suwannacoochee Dolostone; Ellaville, Suwannee County, Florida. REFERENCE LOCALITIES e ... Ellaville Limestone; Ellaville 1 (W-10657), Suwannee County, Florida. f ... Suwannee Limestone; Suwannee River, Suwannee County, Florida.
g ... Ellaville Limestone, Suwannacoochee Dolostone, and Suwannee Limestone; Bass 1 (W-10480), Madison County, Florida
CORE SITES AND WELL SITES e ... Ellaville l(W-10657); Suwannee County, Florida. g ... Bass 1 (W-10480), Madison County, Florida. 49... Lake Talquin 1 (W-6890); Leon County, Florida. 50... Owenby 1 (W-7472); Gadsden County, Florida. 51... well cuttings, W-4 and W-6217; Gadsden County, Florida. 52... Gregory 1 (W-7528); Gadsden County, Florida. 53... Green 1 (W-6937); Leon County, Florida. 54... National Lead 1 (W-12360); Bradford County, Florida. 55... Dupont 1 (W-10488); Clay County, Florida. 56... Hawthorne 1 (W-11486); Alachua County, Florida. 57... Baywood 1 (W-8400); Putnam County, Florida. 58... Wall2 (W-7458); Liberty County, Florida.
8

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Explanation of Symbols on Figure 5 TYPE LOCALITIES G ... Marianna Limestone; Marianna, Jackson County, Florida. H ... Florala Limestone Member of the Bridgeboro Limestone; Florala, Covington County, Alabama. REFERENCE LOCALITIES
h ... Florala Limestone Member of the Bridgeboro Limestone; Mathis 1 (W-8102), Walton County, Florida.
i ... Florala Limestone Limestone Member of the Bridgeboro Limestone; Brown 1 (W-8104), Walton County, Florida.
j ... Bridgeboro Limestone; Hunt 1 (W-10954), Washington County, Florida. k ... BridgeboroLimestone; Limepit at Duncan Church, Washington County, Florida. CORE SITES h ... Mathis 1 (W-8102), Walton County, Florida. i ... Brown 1 (W-8104), Walton County, Florida. j ... Hunt 1 (W-10954), Washington County, Florida. 59... Oak Grove 1 (W-10833); Okaloosa County, Florida. 60 ... St. Regis 1 (W-8103); Walton County, Florida. 61 ... Shoal River 1 (W-8354); Walton County, Florida. 62 ... Eglin 1 (W-8351); Walton County, Florida. 63 ... LaLonde 1 (W-8877); Walton County, Florida. 64 ... Holloway 1 (W-8356); Walton County, Florida. 65 ... Bunge 1 (W-8019); Walton County, Florida. 66 ... Bayview 1 (W-8478); Walton County, Florida. 67 ... Miller 1 {W-7973); Walton County, Florida. 68 ... Ryan 1 (W-8355); Walton County, Florida. 69 ... Sam 1 (W-8876); Walton County, Florida. 70 ... Bruce 1 (W-8592); Walton County, Florida. 71 ... Duncan Church 1 (W-11487); Washington County, Florida. 72 ... Alum Bluff 1 (W-6901); Liberty County, Florida. 73 ... Wall1 (W-7457); Liberty County, Florida.
10

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Although oil and gas exploratory well-cuttings were not studied for this report, I have relied heavily on the data and interpretations of Herrick (1961), Herrick and Vorhis (1963), Applin and Applin (1964), and McFadden and others (1986).
In theexecutionof the present study, stratigraphic sections were measured along the Suwannee River from Dowling Park, Suwannee County, Florida, almost to White Springs, Columbia and HamiltonCounties, Florida. In addition, the Withlacoochee River, a tributary of the Suwannee River, was traversed and numerous sections were measured northward from its confluence with the Suwannee River at Ellaville, to the Parachucla outcrop (Tampa Limestone of Fortson and Navarre, 1959), along the river in Brooks and Lowndes Counties, Georgia. Sections of Suwannee Limestone in the vicinity of Brooksville in Hernando County, Florida, a classical regionforthestudyofthe SuwanneeLimestone (Mansfield, 1937; Yon and Hendry, 1972; Randazzo, 1972; Hunter, 1972), and exposures of the Suwannee Limestone (Jacksonboro limestoneofDall and Harris, 1892)in Screven County, Georgia, were also examined and sampled for foramiiriferal content. The exposures of the Oligocene limestones and residuum in Pulaski and Houston Counties, Georgia, were examined. Various exposures of Oligocene limestone along the Pelham Escarpmen.t and in caves near the Pelham Escarpment from the vicinity of Cordele, Crisp County, southwestward to Oim~ Cave in Decatur County, Georgia, were examined or measured. Many exposures of Oligocene residuum were examined intheDoughertyPlainarea and northeastward through Randolph, Sumter, and Terrell Counties to Bleckley County; and in eastern Georgia in Screven and southern Burke Gounties.
In the eastern Gulf Coastal Plain, Oligocene sections from Vicksburg, Mississippi, Wayne County, Mississippi; Washington, Jackson, Monroe, Conecuh, Covington, and Escambia Counties, Alabama; and Jackson and Washington Counties, Florida, were examined, measured, and sampled for foraminiferal content. Sections of the Oligocene Cooper Formation from various localities in Dorchester County, South Carolina, were also examined and sampled for foraminiferal content.
Paleontological correlation was based on both microfossils and macrofossils. The microfossils employed were primarily the foraminifera, both planktonic and benthic, but dinoflagellates aided biostratigraphic correlation within the Gulf Trough. The Oligocene planktonic foraminiferal zonation scheme of Stainforth and others (1975) was adopted in this study butthe zonations of Bolli (1957) and Blow(1969)werealsoconsidered. The macrofossils employed in correlation were the mollusks (Dall, 1916; Mansfield, 1937, 1938; Dockery, 1982; MacNeil and Dockery, 1984) and echinqids (Cooke, 1942, 1959). Despite the Oligocene molluscan assemblage being vastly

more diverse than the echinoid assemblage,the echinoids havebeenalmost as importantincorrelationofOligocene deposits as the mollusks due to their widespread distribution.
Standard field, laboratory, and paleontological procedures were followed throughout the investigations that led to this report. In field descriptions, the terminology of Ingram (1954) is used for bedding thickness, the Wentworth (1922) scale for grain-size, and the Munsell Color System for describing sediment or rock colors (Rock-Color Chart Committee, 1963). Field approximations for describing degree of sand sorting are employed in this report. =
OLIGOCENE CORRELATION PROBLEMS
Despite the common micro- and macro-fossiliferousOligocenedeposits in the southeasternUnitedStates, precise and detailed biostratigraphic and chrono-stratigraphic correlation between the eastern Gulf Coastal Plain in Mississippi (the type provincial Oligocene of eastern North America) and Alabama, eastward through the. panhandle of Florida, the Gulf Trough, the Florida Platform in Georgia and Florida, to South Carolina and the continental shelf of Georgia has been difficult to achieve. The factors that contribute to this difficulty are both paleontological and stratigraphic-sedimentological in nature. The paleontological factors are as follows:
(1) Globally, the Oligocene planktonic foraminiferal faunas are characterized by low diversity and slow rates of evolution, and the Oligocene Epoch has relatively few planktonic foraminiferal zones. As a consequence, in Coastal Plain deposits, it has been possible only to distinguish readily ,.between the Lower Oligocene (Vicksburgian) and the Upper Oligocene (Chickasawhayan) and, with considerable difficulty and some uncertainty, between the lower and upper Vicksburgian. In the Lower Oligocene Vicksburgian deposits, I have been able to satisfactorily differentiate between lower Vicksburgian and upper Vicksburgian planktonic foraminifera on the basis of the presence of Globorotalia increbescens and Pseudohastigerina barbadoensis or on the consistent absence of these species, on the abundance of Globigerina eocana and the Globorotalia increbescen plexus, and on the very gradually increasing presence of Globigerina ampliapertura through the Vicksburgian. The planktonic foraminiferal suite of the Chickasawhayan is noticeably different than the planktonic foraminiferal suite of the Vicksburgian, based on species presence and absence. The Chickasawhayan is not divisible at the present time based on planktonic foraminifera.
(2) Most of the Oligocene formations in Georgia

12

lack planktonic foraminifera, which are known to occur only in the Ochlockonee Formation and Okapilco Limestone within the GulfTrough, theLazaretto CreekFormation in eastern Georgia, and the Cooper Formation under the outer continental shelf of Georgia. I have not seen any planktonic foraminifera in Oligocene formations from the Florida Bank deposits in either Georgia or Florida. As a result, it is impossible to place most of the Oligocene formations of the region into a biostratigraphic or chronostratigraphic framework based solely on planktonic foraminifera.
(3) Although there have been numerous paleontological reports published on Oligocene fossil groups from the eastern Gulf Coastal Plain, there have been few paleontological investigations of the Oligocene of the Florida Platform, and no paleontological investigations on the Oligocene of the southern Atlantic Coastal Plain south of North Carolina. As a result, many of the conclusions in this report concerning faunal distributions in Oligocene deposits of the Florida-Georgia region are based on my own previously unpublished observations in conjunction with theinfortnationavailable in the literature. Based on the current literature alone, it is not possible to correlate regionally within the Oligocene at finer resolution than Epoch or Series.
(4) The distribution of Oligocene benthic foraminiferal species in the southeastern United States is primarily a function of paleoenvironment (also see Huddlestun, Hunter, and Carter [1988] and Dockery, [1988]). Superimposed on and directly related to the paleoenvironmental control on foraminiferal distribution is the presence and overlap of three faunal provinces (or subprovinces). Because of the absence of demonstrated Upper Oligocene (Chickasawhayan) deposits in Georgia, the local occurrences of deep-water Upper Oligocene deposits in South Carolina, and reported occurrences of Upper Oligocene deposits in peninsular Florida (Mansfield,1937,1938;Cooke,1945), itisnotcleartowhat degree temporal differences may have had an impact on Oligocene smaller benthic foraminiferal distributions across the region.
The Gulf of Mexico faunal province during the Early Oligocene encompassed not only the faunas of the typical eastern Gulf Coastal Plain deposits (Vicksburg Group) but also the Gulf Trough deposits (at this time little is known of the benthic foraminifera of the Bridgeboro Limestone). Within the Gulf of Mexico faunal province, two general types of benthic foraminiferal assemblages occur: a relatively shallow-water assemblage and a deeper water assemblage (compare with Hazel and others, 1980). The deeper water assemblage is characteristic of the Red Buff Clay and its calcareous stratigraphic equivalent in southwestern Alabama (Bumpnose Limestone of Hazel and others, 1980), the Marianna and Glendon Limestones in Alabama, and the Ochlockonee

Formation in Georgia and Florida. The shallow-water assemblage is characteristic of the Mint Spring Formation and GlendonLimestoneinwesternMississippi, the Byram Formation, the Bucatunna Clay, the Okapilco Limestone, the Bumpnose and Marianna Limestones in Jackson County, Florida, and the Marianna and Glendon Limestones in Georgia. Apparently lithofacies, biofacies, and bathymetry were not strongly coupled during the Vicksburgian because the Marianna and Glendon Limestones ofGeorgia, and the Glendon Limestone in western Mississippi are characterized by shallow-water foramini:.. feral populations in contrast to the moderately deep water assemblages of the same formations in Alabama. As a result, at the present level of knowledge of benthic foraminiferal distributions in Vicksburgian deposits in the eastern Gulf Coastal Plain, detailed biostratigraphic correlation within the Vicksburgian based on benthic foraminifera is not yet attainable.
The Oligocene benthic foraminiferal suites of the Florida Bank can be characterized as a fauna that contains some typical benthic foraminiferal species of the eastern Gulf of Mexico continental shelf deposits (Vicksburg Group) in addition to some species that appear to be endemic to the Florida Bank. Therefore, the Oligocene (Vicksburgian) benthic foraminiferal fauna of the Florida Bank appears to consist of a mixture of eastern Gulf of Mexico continental shelf species and indigenous Florida Bank (Caribbean or Tethyan) species. All of the known indigenous species and the continental shelf foraminiferal species of the Florida Bank (compare with Horowitz, 1979) appear to be long ranging. In addition, no deeper water, Oligocenebenthic foraminiferal faunas are known from the Florida Bank in Georgia or Florida. As a result, detailed biostratigraphic correlation between the Vicksburg Groupof the eastern Gulf of Mexico continental shelf, and the shallow-water carbonates of the Florida Bank has not yet been attained. Little is currently known of the Oligocene benthic foraminiferal assemblages of the Atlantic faunal province. The deep-water foraminiferal fauna of the Upper Oligocene Cooper Formation in South Carolina (Ashley Member of Ward and Blackwelder, 1979) and contine:t:1tal shelf of Georgia cannot be directly related to the coeval shallow-water foraminiferal fauna of the Chickasawhay Formation or Paynes Hammock Sand (Poag, 1966) of the eastern Gulf Coastal Plain. The deepwater foraminiferal fauna of the Lower Oligocene component of the Cooper Formation on the continental shelf of Georgia (in the TACTS cores and in core AMCOR 6002) is also different (probably deeper water) from the coeval deep-water foraminiferal faunas of the correlative Red Bluff Clay, Marianna and Glendon Limestones of Alabama, and the Ochlockonee Formation of Florida and Georgia, thus permitting only general biostratigraphic correlation. Finally the shallow-water benthic foraminiferal fauna of the Lazaretto Creek Formation of eastern

13

Georgia has less diversity, greater faunal dominance, tion-Red Bluff Clay make up the lowest series of forma-

and has a generally different faunal make-up in terms of tions of the group. The Bumpnose Limestone of Alabama

species proportions than correlative Vicksburgian as- and western Florida (Moore, 1955; not the Bumpnose of

semblages ofthe eastern Gulf ofMexico continental shelf. Hazel and others, 1980) is also part of this series but is not

The foraminiferal fauna ofthe Lazaretto Creek Formation a part of the Vicksburg Group because it is an Ocala-like

has little in common with that of the Suwannee Lime- limestone. The Mint Spring Formation-Marianna Lime-

stone, even though the two formations appear to be stone make up the overlying series of formations; the

gradational with each other over a short distance (see Pl. Glendon Limestone regionally and conformably overlies

4). The benthic foraminiferal faunas of the Atlantic prov- the Mint Spring Formation-Marianna Limestone; the

ince, therefore, can be correlated only approximately Byram Formation overlies the Glendon Limestone, and

with Oligocene, Vicksburgian deposits of the Florida the Bucatunna Oay is the uppermost formation of the

Platform(Florida province) and theeasternGulfofMexico Vicksburg Group (Pl. 1). Most of these formations can be

continental shelf (Gulf of Mexico province).

traced and correlated from Mississippi to central Ala-

(5) The macrofossils of the Oligocene appear to .bama and western Florida, with outliers of Marianna

be of greater biostratigraphic value than the foraminifera Limestone and Glendon Limestone in central Georgia

in establishingregional correlation. However, as with the north of the Gulf Trough. The northern flank of the Gulf

foraminifera, the macro-fossils areuseful onlyat the stage Trough and the projected vicinity of the Peninsular Arch

level (Vicksburgian and Chickasawhayan) and have not defines the eastern limit of the Vicksburg Group of the

yet been shown to be useful in correlation at much finer eastern Gulf Coastal Plain. The Vicksburg Group grades

resolution. Based on the mollusks and echinoids, all of laterally southward, offshore, into the Florala Member of

theunweathered GeorgiaOligoceneformationsareshown theBridgeboro Limestonein southern Alabama andwest-

to be compatible with the Vicksburgian and not with the ern Florida. None of the formations of the Vicksburg

Chickasawhayan.

Group occur within, south, or east of the Gulf Trough.

TheupperpartoftheSuwannee Limestonein the

Sea level regressions with the accompanying

Brooksville area of peninsular Florida (Mansfield, 1937; disconformitiesare postulated to constrainthe four strati-

Yon and Hendry, 1972) has been reported to contain a graphic assemblages of the Vicksburgian in the eastern

younger Oligocene molluscan assemblage and, there- Gulf coastal Plain. These events are considered to be

fore, was correlated with the Upper Oligocene synchronous across the region and, therefore, the various

Chickasawhay Formation (Mansfield, 1937, 1938; Cooke, deposits between the disconformities are considered also

1945). Dall (1916), Mansfield (1937), and Cooke (1943) to be approximately synchronous.

identified some of these younger Oligocene mollusks of

A different association of formations is present

the peninsular Florida Suwannee Limestone in chert on the Florida Bank east of the GulfTrough. In ascending

residuum ofsouthwestern Georgia and concluded that order, these formations include the Ellaville Limestone,

the residuum is correlative, therefore, with the upper Suwannacoochee Dolostone, and Suwannee Limestone.

Suwannee Limestone of peninsular Florida. Because The upper part of what has been mapped as Ocala Lime-

these deposits in peninsular Florida and southwestern stone also may be of Early Oligocene age and correlative

Georgia occur at the tops of some local geologic sections, with the Red Bluff-Bumpnose (Hunter, 1976). There is

the faunas were correlated with the Chickasawhay For- some reason to believe that these formations are wide-

mation. However, the Chickasawhay Formation of Mis- spread on the platform and can be traced in outcrop or the

sissippi is only sparsely macrofossiliferous and doesnot shallow subsurface over wide areas ofnorthwestern pen-

contain the characteristic upper Suwannee mollusks of insular Florida and southwestern Georgia. The basal

Florida, which appear to be restricted largely to the Ocala-like limestone, the Ellaville Limestone and the

Florida Bank (but some elements of the fauna have been Suwannacoochee Dolostone appear to be the least exten-

identified from residuum as far westas central Alabama). sive of the platform formations whereas the Suwannee

I conclude, therefore, that macrofossil correlation of Limestone can be traced intermittently from the vicinity

Chickasawhayandepositsbetween Mississippi, Alabama, of Brooksville in Hernando County, Florida, atleast as far

and the Florida Platform of Florida and Georgia has not northeastward as the Savannah River in Georgia. Oligo-

yet been established.

cene formations are absent in southeastern-most Georgia

Correlation by lithology and stratigraphic posi- and the eastern p~rt of the peninsula of Florida. As with

tion, coupled with biostratigraphic correlation, appears the Vicksburg Group on the continental shelf to the

to be a reliable means of detailed correlation within the northwest, correlation by lithology and stratigraphic po-

Vicksburg Group of the eastern Gulf Coastal Plain. The sition at this time appears to be a reliable means of

formations of the Vicksburg Group are restricted to the detailed correlation of Oligocene formations on the plat-

continental shelf of the eastern GulfofMexico and consti- form, but biostratigraphic correlation has yet to be tied

tute a stratigraphic association. The Forest Hill Forma- closely to physical correlation.

14

The Gulf Trough contains a separate suite (stratigraphic association) of lithostratigraphic units, distinct from that of the continental shelf to the west and north (Vicksburg Group), and distinct from that of the Florida Bank to the east and south. There are also pronounced differences in elevations of Oligocene formations within the Gulf Trough compared with the elevations of the correlative formations outside of the trough (see Pl. 2). Therefore, correlation by lithology is not possible; and correlation by stratigraphic position is unreliable between formations within the trough and those on either side of it, and between formations across the trough. Those Oligocene lithostratigraphic units restricted to the Gulf Trough include the Ochlockonee Formation, Wolf Pit Dolostone, and Okapilco Limestone. The Bridgeboro Limestone is restricted in occurrence to both northern and southern flanks of the trough and is not found more than approximately 20 or 30 miles (32 or 48 km) from the Gulf Trough in south Georgia. Biostratigraphic correlation remains the only reliable means of correlation between the Oligocene stratigraphic units within the trough and those outside it.
The Lazaretto Creek Formation of the Atlantic continental shelf stratigraphic association grades laterally westward into Suwannee Limestone (Pl. 3) and, therefore, is physically correlative with the Florida Bank formations. Correlation of the Lazaretto Creek Formation to the standard VicksburgGroupis achieved through itslateralgradationwith the SuwanneeLimestone. In this report, the Cooper Formation of South Carolina and the Atlantic continental shelfofGeorgia is correlated with the standard provincial Oligocene section in the eastern Gulf Coastal Plain through planktonic foraminifera and not through physical correlation.
In summary, regional correlation of Oligocene deposits in southeastern North America is impeded by (1) lack of modern, rigorous, definitive biostratigraphic and paleontological studies across the region, (2) irregular and sparse occurrence of planktonic microfossils in Oligocene formations, (3) pronounced paleobathymetric changes within formations along the outcrop belt and, therefore, the weakened utility of benthic micro- and macrofossils in correlation, and (4) the presence of three faunal provinces (or subprovinces) with different and distinct micro- and macrofaunas.
LITHOSTRATIGRAPHY
EASTERN GULF OF MEXICO STRATIGRAPIDC ASSOCIATION
VICKSBURG GROUP

Plain that range from noncalcareous, argillaceous sand to . sandy clay and variably calcareous clay (Forest Hill Formation, Bucatunna Clay and Red Bluff Clay) to fossiliferous, calcareous, argillaceous sands (Mint Spring Formation and Byram Formation), to relatively pure, variably macrofossiliferous limestones (Marianna Limestone and Glendon Limestone). In contrast to the various codes of stratigraphic nomenclature (American Commission on Stratigraphic Nomenclature,[1961, 1970]; International Subcommission on Stratigraphic Classification [1976]; North American Commission on Stratigraphic Nomenclature [1983]), it is not the similar lithplogies or common lithologic features that serve to unite the above formations into onegroup. TheVicksburgGroupdeposits bear a common fauna and it is the common fauna that is the real basis of the group. In accord with the common Vicksburg fauna, Murray (1961 p. 394-395) proposed changing the sense of the name Vicksburg from lithostratigraphic unit (Vicksburg Group) to chronostratigraphic unit (Vicksburgian Stage):
Since Vicksburg has no real lithologic unity in its present broad application and has been widely employed in essentially a time-rock (timestratigraphic) sense, it is used herein as a provincial stage in the Atlantic and Gulf coastal region to include all beds which can be reasonably demonstrated as equivalent to the type Vicksburg and its characteristic divisions which are wholly or in part exposed in and around the city of Vicksburg, Warren County (Mississippi).
The name Vicksburg is still applied as a lithostratigraphic unit inMississippi and Alabamawhere the formations of the original Vicksburg Group can be identified and traced. In Georgia, however, theVicksburg Group consists only of outliers of Marianna Limestone and Glendon Limestone, and none of the formations of the Vicksburg Group are present in peninsular Florida where stratigraphicallyequivalentformationsarepresent. The Vicksburgian fauna, upon which the Vicksburgian Stage is ultimately based, is present in Georgia and peninsular Florida. As a result, the Vicksburgian chronostratigraphic unit is more applicable in this region than the name Vicksburg Group. Because the Marianna and Glendon Limestones are present in Georgia, the sense of the Vicksburg Group is retained in Georgia in this report.

Definition

Type Area

The Vicksburg Group is a lithologically hetero-

The Vicksburg Group is named from the city of

geneous suite of formations of the eastern Gulf Coastal Vicksburg, Warren County, Mississippi (Conrad, 1848a,

15

1848b;Murray,1%1;Dockery,1982;MacNeilandDockery, Formation (Veatch and Stephenson, 1911, p. 322-323),

1984; Fisher and Ward, 1984), where the Forest Hill For- Flint River formation (Cooke, 1943, p. 83), unit B of the

mation, Mint SpringFormation, Glendon Limestone, and ByramFormation(Pickering,1970,p. 34-35),and Marianna

Byram Formation are exposed in and about the city of Limestone (Huddlestun, and others, 1974; Glawe, 1974).

Vicksburg and in the bluffs overlooking the Mississippi In the Chattahoochee Embayment in southwestern Geor-

River.

gia, the Marianna Limestone of Sever and Herrick (1967)

and the Marianna Limestone equivalent of Zimmerman

Lithology

(1977) are the Ochlockonee Formation of this report.

The Vicksburg Group is lithologically heterogeneous in Type Section

the type areainMississippi and in Alabama. However, in

Pulaski County, Georgia, the group consists only of rela-

Matson and Clapp (1909) did not specifically

tively pure limestone of the Marianna Limestone and designate a type locality for the Marianna Limestone.

Glendon Limestone (see Pickering, 1970, p. 51).

However, they included measured sections from expo-

sures "near the east edge of the town of Marianna"

Stratigraphic Relationships

(Matson and Clapp, 1909, p. 57) that were considered by

Mossom (1925, p. 71) and Cooke and Mossom (1929, p. 63,

The Vicksburg Group is restricted to the eastern 65) to be the type locality. This site is on the right bank1

Gulf Coastal Plain west and north of the Gulf Trough. In of the Chipola River where, "roads leading to the old

Georgia, the Vicksburg Group is restricted in known bridge and to the new bridge (built in 1927) have been cut

occurrence to the vicinity of Hawkinsville in Pulaski through the rock" (Cooke and Mossom, 1929, p. 65). The

County (Fig. 2). It is possible, however, that Vicksburg type section or unit-stratotype of the Marianna Lime-

Grouplimestonesoccuralonga southwest-northeastband stone, then, is that section of Marianna Limestone ex-

from the vicinity of Hawkinsville southwestward some posed in low bluffs along the west bank of the Chipola distance. It also seems likely that at one time, the occur- River near the U.S. 90 highway bridge on the east side of

rence of the Vicksburg Group may have been continuous Marianna, Florida, in SE1/4, Sec. 3, T4N, RlOW (Fig. 6).

across theDougherty Plainfrom JacksonCounty,Florida,

northeastward to Pulaski County.

Lithology

Age

The Marianna Limestone in Pulaski County,

Based on the occurrence of Clypeaster rogersi, Georgia, is lithologically typical for the formation and is

Paraster americanus, Chlamys anatipes, C. duncanensis, and essentially the "chimney rock" (Matson and Clapp, 1909,

I.epidocyclina mantelli (Pickering, 1970; Glawe, 1974), the p.58;Mossom, 1925,p.44,45,73;Cooke,1945,p.76,77)

Vicksburgian sediments of Georgia are correlated with of the type area. The Marianna is finely granular with

typical Vicksburgian sediments in Mississippi and Ala- substantial interstitial''limepaste" or micrite and is chalky

bama. In the eastern Gulf Coastal Plain, the Vicksburg in appearance. The grain-size of the granular or arenitic

Group is correlated with the Rupelian Stage and is in- material, which is of bioclastic origin, ranges from very

cluded in the Cassigerinella chipolensis-Pseudohastigerina fine to fine on the Wentworth scale. Fossils, particularly

miCra Zone of Stainforth and others (1975) (Pl. 1).

I.epidocyclina, some bryozoa, scattered Clypeaster rogersi,

MARIANNA LIMESTONE

and mollusk molds supply the only coarse, bioclastic material. The limestone is variably macrofossiliferous,

Definition

with some intervals being virtually nonmacrofossiliferous. In general, the Marianna Limestone in PulaskiCounty is

poorly but variably fossiliferous. The Marianna Limestone was named by Matson

and Clapp (1909, p. 52-59) for a Vicksburg-related lime-

stone formation typically exposed in the vicinity of

Marianna in Jackson County, Fiorida. In Georgia, the

only known occurrence of Marianna Limestone is in a

small area in and immediately south of Hawkinsville in

Pulaski County. It is well-exposed along the Ocmulgee River on thesouth side ofHawkinsville and in river bluffs 1.2 miles (2 km) south of Hawkinsville. In the past, the limestone in these bluffs was referred to the Vicksburg

1 The convention concerning "left bank" and "right bank" of a river is as
follows: facing downs~eam, the ''left bank" is that bank on the left side
of the river, and the "rightbank" is thatbank on therightsideof the river.

16

.5

0

.5

0

1 MILE KILOMETER

Figure 6. The type locality of the MariannaLimestone (U.S. Geological Survey, Marianna, Fla. 1:24,000 topographic quadrangle).
17

The limestone is unconsolidated and soft, but coherent. Minor induration occurs in thin layers, especially where there are concentrations of Lepidocyclina. The Marianna Limestone is massive and thick-bedded, with only some thin, vague stratification defined on differences in fossil content.
Accordingto Pickering (1970, p. 51), the Marianna Limestone consists of 98.41 percent calcium carbonate. No other lithic component has been observed in the Marianna although there is probably a trace of silt and clay present (compare with Pickering, 1970, p. 51).
Stratigraphic relationships
The Marianna Limestone in Georgia probably occurs near the eastern limit of the formation because the Oligocene calcareous sand and sandy limestone is present roughly 45 miles (72 krn) farther east in Wheeler County. No other occurrences of the Marianna Limestone are knownbetweencentralPulaski County and the type area in central Jackson County, Florida, a linear distance of approximately 150 miles (240 km). A projected outcrop belt of the Marianna Limestone between Pulaski County, Georgia, and Jackson County, Florida, would occuralong the center of the Dougherty Plain where all Oligocene deposits have either been eroded or weathered to residuum. Significantly, residuum of Bridgeboro Limestone can be traced northwestward only as far as Albany. The Marianna Limestone is projected to have occurred farther to the northwest in the past (Fig. 7). It is possible that the Marianna Limestone once formed a continuous outcrop belt from Jackson County, Florida, at least as far northeast as the Ocmulgee River area. The Marianna Limestone in Pulaski County would represent an outlier or remnant of the once-continuous formation.
The Marianna Limestoneparaconforrriably overlies the Upper Eocene Ocmulgee Formation in Pulaski County. In tum, the Mariannais conformablyoverlainby Glendon Limestone, or is disconformably overlain either by Hawthorne Group deposits or by residuum. The presence of Glendon Limestone on the Ocmulgee River suggests that Glendon Limestone may overlie the Marianna in the subsurface, but this superposition has not yet been observed in cores.
The Marianna Limestone is a soft, chalklike,massive, sparsely but variably fossiliferous limestone. It is the same as the "chimney rock" of Florida and Alabama. The underlying Ocmulgee Formation is more lithologically variable, tough and partially consolidated, granular,variablyglauconitic,argillaceouslimestone with commonly occurring bryozoa. The overlying Glendon Limestone is distinguished from the Marianna in consisting of alternating layers of indurated limestone (ledges) and soft, unconsolidated limestone (reentrants). In Pulaski County the Glendon is almost nonrnacrofossiliferous. All

other overlying deposits consist mainly of weathered clays and sand.
Although the upper and lower contacts of the Marianna Limestone are present in the river bluffs in the vicinity of Hawkinsville, the entire section is not exposed in any single outcrop. The entire Marianna Limestone is, however, present in the core Pulaski 3 (GGS-3111) in the interval75 feet to 96 feet and is 21 feet (6.5 m) thick (also see Huddlestun and others, 1974, p. 27). It disconformably overlies deposits of the Hawthorne Group, the Glendon being absent at the core site. The Marianna Limestone in Georgia was deposited on the inner continental shelfin an area devoid of siliciclastic sediments. It appears to grade landward into siliciclastic-rich, coastal deposits, and itappears to grade seaward into more open marine Bridgeboro Limestone.
Age
The age of the Marianna Limestone is Early Oligocene (Rupelian), middle Vicksburgian. The fauna documented from the Marianna Limestone at Hawkinsville is compatible with that of the Marianna Limestone fromFlprida, Alabama, and Mississippi. Critical species include the following (Pickering, 1970, 20-24; Glawe, 1972, p. 11):
Clypeaster rogersi Paraster americana Chlamys anatipes C. duncanensis
Oligocene foraminifera reported from the MariannaLimestone at Hawkinsville include:
Lepidocyclina mantelli Pararotalia byramensis
The Marianna Limestone in Georgia is barren of planktonic foraminifera. However, planktonic foraminifera I have identified from the Marianna Limestone at St. Stephens Quarry in Washington County, Alabama include:
Globorotalia increbescens G!obigerina ampliapertura
G: eocaena
G. officinalis G. ouachitaensis G. ciperoensis Globorotaloides suteri Pseudohastigerina barbadoensis Chiloguembelina cubensis
This assemblage is consistent with the Cassigerinella

18

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t

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at Mexico

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miles

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MARION

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Figure 7. The areal distribution (outcrop and subcrop) of the Marianna Limestone in Georgia and northern Florida.
19

chipolensis-Pseudohastigerirtil micra Zone ofStainforth and others (1975),(Pl. 1) and with planktonic foraminiferal Zones P17-P19 of Blow (1969).
GLENDON LIMESTONE
Definition
The Glendon Limestone was named by Cooke (1918) for limestone of Vicksburgian age that overlies the Marianna Limestone in Alabama. In Georgia, the only known occurrence of the Glendon Limestone is in a bluff on the Ocmulgee River near Hawkinsville in Pulaski County. In the past, the Glendon Limestone at this site had been included in the Vicksburg formation (Veatch and Stephenson, 1911), undifferentiated Eocene and Oligocene (Brantly, 1916), Flint River formation (Cooke, 1943), unit A of the Byram Formation (Pickering, 1970) and Glendon Limestone (Huddlestun and others, 1974; Huddlestun, 1981).
The name Glendon was onceapplied extensively to limestones and residuum in southwestern Georgia. Cooke (1923) referred the chert-bearing deposits in the Bainbridge area to the Glendon Limestone on the basis of the postulated correlation of faunas of the Glendon Limestoneof Alabama withthat of the chert-bearingresiduum of southwestern Georgia. Later, Cooke (1935) developed doubts, onpaleontological grounds, concerningthe identificationand correlation ofthe residual deposits ofsouthwestem Georgia with the Glendon Limestone. He postulated that the southwestern Georgia deposits contain a foraminiferal and coralline assemblage that was more similar to the Antigua Limestone of the British West Indies. Cooke (1935), therefore, abandoned the name Glendon in Georgia and assigned the chert-bearing residual deposits and associated limestones (Bridgeboro Limestone of this report) to the Flint River formation.
Type Section
The type locality and unit-stratotype of the Glendon Limestone is an abandoned and overgrown limestone quarry north of the abandoned Glendon flag station on the Southern Railroad between Jackson and WalkerSpringsinNE1/4,Sec.2, T6N,R2E,ClarkeCounty, Alabama.
Lithology
Near its type area in eastern Mississippi, the lithologyofthe GlendonLimestone hasbeendiscribed by Thomas (1948, p. 20-21) as follows:
... where the facies consists of 15 to 20 feet of hard, fossiliferous crystalline limestone (locally

called "horsebone") with softer marl interbeds. In the Vicksburg area the beds correlated with the typical Glendon consists of 15 to 40 feet of hard, sandy, glauconitic fossiliferous limestone with softer marly interbeds and, locally, a thin bentonite bed. The lithology of the Glendon at Vicksburg differs from typical Glendon in being more sandy and less crystalline, with the absence of the 'horse bone' weathering effect.
Hendy (1948, p. 28) described the Glendon Limestone in Wayne County, Mississippi as follows:
Above the Marianna the section consists of 15 to 30 feet of hard, crystalline, glauconitic lime or marl. This rock, when fresh, has a light blue color and on weathering changes to creamy yellow, buff or tan. The basal part, about 6 feet thick, is very irregularly indurated and on weathering has a "horsebone" characteristic similar to that associated with the weathered limestone of the Glendon in the type area in western Alabama. The typical upper part is composed of ledges of crystalline lime which thicken and thin and often have concretionary like projections, the ledges being separated by soft marl partings. Locally in the upper part induration is very irregular but "horse bone" does not form on weathering. Overlying the highest, crystalline, limestone ledge are 1 to 3 feet of soft, light blue-gray, slightly argillaceous marl, which is lithologically similar to the partings between the limestone ledges below.
There are no evident breaks in deposition within the section, although the basal "horse bone" limestone which is gradational with the section above has a distinct characteristic when weathered. No break exists between the highest limestone ledge and the soft lime which overlies it; however, this contact is very evident on drillers' and electrica logs.... This section rests conformably and gradationally on the Marianna. An

20

interval 2 to 3 feet thick is present in

neyrock).

which the soft Marianna lime becomes

There is roughly 10 feet (3 m) of Glendon Lime-

harder and denser, grading upward

stone exposed on the Ocmulgee River. The Glendon

into a noncrystalline, chalky, hard lime

Limestone in Georgia was deposited in relatively shal-

and thence into "horse bone: at the

low, offshore, normal and open-marine, continental shelf

base of the Byram. (= Glendon of this

water in an environment almost free from siliciclastic

report)

sediments.

Along the Ocmulgee River, the Glendon Lime-

and NacNeil and Dockery (1984, p. 20):

stone overlies the Marianna Limestone with apparent

conformity, but the contact can be seen only at very low

The Glendon Limestone is a hard, ledge-

water stages of the river (Pickering, 1970, Fig. 9). The

forming limestone ...

Glendon is overlain by surficial sand in outcrop. If the

Glendon Limestone is present elsewhere in the

The Glendon Limestone on the Ocmulgee River Hawkinsville-Cordele area, it would probably be over-

consists of alternating hard and soft layers (ledges and lain either by Oligocene residuum, by Hawthorne Group

reentrants) of limestone. The limestone in the ledges is deposits, or by river terrace deposits.

partially recrystallized and consists of approximately 94

percent calcium carbonate (Pickering, 1970, p. 51). The Age

limestone in the reentrants is argillaceous, silty, consists

of approximately 70 percent calcium carbonate, and con-

The Glendon Limestone is Early Oligocene,

tains conspicuous carbonaceous material. The Glendon Vicksburgian (Rupelian) in age. The only fossils that

Limestone on the Ocmulgee River differs from typical have been identified from the Glendon Limestone on the

Glendon Limestone in being very sparsely Ocmulgee River are all very rare and include Paraster

macrofossiliferous, and it does not contain any signifi- . americanus, fragments of an echinoid that appears to be

cant number of Lepidocyclina as is characteristic of the Clypeaster rogersi, Lepidocyclina, and molds of the gastropod

formation in Alabama. The soft limestone, however, is Xenophora (Pickering, pers. com., 1983). As reported, the

abundantly microfossiliferous.

meager fauna of the Glendon Limestone is consistent

with a Vicksburgian age (Pl. 1).

Stratigraphic Relationships

SHELLSTONE CREEK BEDS, new informal name

The Glendon Limestone is known to occur only

in one outcrop in Georgia, the most-downstream bluff on Definition

the right bank of the Ocmulgee River approximately 1.25

miles (2.0 km) southeast of Hawkinsville, Pulaski County

The Shellstone Creek beds consist of moderately

(Fig. 8)(Pickering, 1970, Pl. 1, locality 38). The Glendon is weathered, chert-bearing, stratified, argillaceous, well-

notpresentin the core Pulaski 3 (GGS-3111) 1.5 mile5(2.4 sorted, fine-grained sand. At this time, the Shellstone

km) from the exposure on the river. Therefore, in the Creek beds have been positively identified only in a

Hawkinsville area, the occurrence of the formation must roadcuton the southernvalley wall of Shellstone Creekin

be spotty. The occurrence of the Glendon Limestone in northern Bleckley County, Georgia (Fig. 9, site

Georgia probably is similar to that of the underlying l)(Pickering, 1970, Pl. 1, locality 2), and at two sites in the

Marianna Limestone (see discussion on p. 18). If so, the Oakey Woods Wildlife Management Area in eastern

Glendon outcrop belt once may have been continuous Houston County, approximately 7 airline miles (11 km)

from central Georgia to the Mississippi River. In this west of the Bleckley County exposure. Shellstone Creek

event, the Glendon Limestone would have been removed beds are exposed at the top of a ravine (Fig. 9, site

either by erosion or dissolution from part or all of eastern 2)(Locality 5 of H!;~ddlestun and Hetrick, 1978, Fig. 6, p.

Alabama, the Florida panhandle, and southwesternGeor- 77), and the upper parts of the beds are exposed in

gia. The Bridgeboro Limestone occursin the stratigraphic another ravine atthe highest elevations in the area (Fig. 9,

position of the Glendon Limestone at Rockhouse Cave site 3). At these sites, where undisturbed stratified sand

southeast of Cordele.

is present, the Shellstone Creek beds have a Barnwell-

The Glendon Limestone is distinguished from type lithology and most nearly resemble stratified argil-

the underlying Marianna Limestone in consisting of al- laceous sands of the Dry Branch Formation. In the past,

ternating layers of hard (ledges) and soft (reentrants) these exposures have been mapped with or described as

limestone. The Marianna, on the other hand, is typically Ocala Limestone and Flint River formation (Cooke, 1939,

massive to thickly and rudely bedded, and consists of 1943), Suwannee Limestone (MacNeil, 1947b), FlintRiver

unconsolidated but firm and coherent limestone (chim- Formation (Pickering, 1970, pl. 1), Suwannee residuum

21

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(Huddlestun and Hetrick, 1978, Fig. 6), and unnamed, thinly bedded, fine sand and clay unit (Huddlestun and Hetrick, 1978; p. 66).
The Shellstone Creek beds present a different stratigraphic problem from that of the Oligocene residuum. Based on the above three sections, if non-chert bearing (nonfossiliferous) ShellstoneCreekbeds occurred widely in the Fall Line Hills in central and eastern Georgia, lithostratigraphically they would be included in the Barnwell Group. And, if the Shellstone Creek beds that are barren of fossiliferous chert occurred farther north and directly overlie the Tobacco Road Sand, it could be difficult to differentiate the two sand units. However, neither stratified sands with Oligocene fossils nor residuum with Oligocene fossils have been identified at other Tobacco Road exposures in central and eastern Georgia. In the Fall Line Hills, typical Tobacco Road Sand either occursat the top ofthe geologic sectionor is directly overlain by the Miocene Altamaha Formation. At some sites and in some areas in central and eastern Georgia, however, well-sorted, fine-grained sand reminiscent of the Shellstone Creek beds occur at the top of the Tobacco Road Sand sections. Because these fine-grained sands are weathered to some degree, lack chert, and are nonfossiliferous, specific age assignments have not been made on them and they have been included and mapped with the Tobacco Road Sand (e.g., Stop 4, beds 5 and 6 of the Tobacco Road Sand in Huddlestun and Hetrick, 1979, p. 51-52).
The Shellstone Creek beds are significant in that, previouslyintheSoutheasternCoastal Plain,no Barnwelltype, stratified, siliciclastic deposits of Oligocene (and especially Vicksburgian) age have been reported. This occurrence adds to the accumulating evidence that the earliest Oligocene environment and depositional systems in the Southeast were very similar to those of the preceding Late Eocene, and that the Vicksburgian lithostratigraphic and distribution patterns are very similar to those of the underlying Jacksonian. It also suggests that Barnwell-type,Vicksburgian depositsoncemayhave been much more widespread in the Fall Line Hills and near the Fall line than is the case now. Finally, it is possible that, locally, the uppermost beds of the Tobacco Road Sand ofthe Barnwell Group may beVicksburgian in age.
Reference Sections
The locations of three exposures of the Shellstone Creek beds are given here for reference purposes. The roadcut at the intersection of Red Dog Road and Magnolia Road on the southern valley wall of the Shellstone Creek in Bleckley County is the main reference section of the Shellstone Creek beds (Fig. 8, site 1). Fossiliferous chert with rare Oligocene fossils occurs in the lower part

of the section whereas the characteristic stratified sand occurs in the upper part of the section. The Shellstone Creek beds are overlain at this site by high terrace, gravelly sand deposits of the Ocmulgee River; but less than 1 mile (1.6 km) to the east on Red DogRoad, residuumwith fossiliferous chert occurs at higher elevations than that at the road intersection. The exposure at the road intersection is located immediately east of the Ocmulgee River, approximately 3.5 miles (5.6 km) southeast of Westlake and 6.5 miles (10.4 km) north-west of Cochran (Fig. 8).
The other two reference sections are located in the Oakey Woods Wildlife Management Area in eastern Houston County, Georgia, west of the Ocmulgee River (Fig. 8, sites 2 and 3). The first section is in the top of a steep-head,about100feet(30m)southofthedirtroad,0.5 mile (0.6 km) southeast of the Kathleen Observation Tower. This is Locality 5 of Huddlestun and Hetrick (1978, Fig. 6). The Shellstone Creek beds-Tobacco Road Sand contact is exposed at this site and most of the ShellstoneCreek beds here consistofstratified to massive chert.
The other section is exposed in a ravine at the intersection of two dirt roads (Fig. 8, site 3). There is no chert exposed atthis localityand the lithology of the sand most nearly resembles that of similarly stratified, argillaceous, fine sands of the Irwinton Sand Member ofthe Dry Branch Formation.
Lithology
In the area being described, the Shellstone Creek beds consist of a lower part with stratified, variably fossiliferous chert and interstratified chert and fine- to medium-grained sand. The upper part consists ofweathered,thinlybedded, argillaceous, well-sorted, fine-grained sand.
Stratigraphic Relationships
The Shellstone Creek beds in northern Bleckley and eastern Houston Counties probably grade laterally southward (seaward) into the Marianna and Glendon Limestones because all are Vicksburgian in age. However, due at least in part to deep weathering and the nearby presence of deeply incised rivers, no other exposures of unweathered to only moderately weathered Oligocene sediments have yet been found between ShellstoneCreek-OakeyWoods and Hawkinsville, where the Marianna and Glendon Limestones are exposed. Therefore I speculate that the zone of lithofacies change occurs in the vicinity of the east-west escarpment (cuesta) that occurs along the trend of Flat Creek-Big Indian Creek-South Shellstone Creek-Perry-Clinchfield (Ocala escarpment of Pickering, 1970, Pl. 1). Numerous Lower Tertiary stratigraphic units undergo a north to south

23

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1-
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Figure 9. Reference locations for the Shellstone Creek Beds (U.S. Geological Survey, Hawkinsville, Georgia, 30 X 60 minute series [topographic]).
24

lithofacies change along this trend, including the lithofacies change of the underlying Tobacco Road Sand southward (seaward) into the Ocmulgee Formation. In addition, enigmatic sands that overlie the Ocmulgee Formation in the vicinity of Sugar Hill in southeasternmost Houston County may represent a paleo-barrier island phase of the Vicksburgian similar to one suggested by Huddlestun and Hetrick (1978, p. 65, 70-72)for the underlying Tobacco Road Sand-Ocmulgee Formation transition. If so, then the postulated Vicksburgian barrier island system would have migrated seaward by about 6 or 7 miles (10 or 11 km) from its Late Eocene position. There is no information concerning the stratigraphic relationships of the Shellstone Creek beds with Oligocene deposits farther east. Much of the massive and structureless, Oligocene residuum in southem Houston, Pulaski, and Bleckley Counties originally may have been an argillaceous, fossiliferous, calcareous phase of the Shellstone Creek beds.
The Shellstone Creek beds overlie the Tobacco Road Sand with sharp contact at Oakey Woods (Huddlestun and Hetrick, 1978, Fig. 6). There is no information from Bleckley County on the nature of the lower boundary, but the same stratigraphic relationship would be expected to be present there too. In eastern Houston County, the Shellstone Creek beds occur at the very top of the local section, but in Bleckley County the sand is overlain by Oligocene residuum that contains scattered layers of fossiliferous to nonfossillferous chert.
In eastern Houston County, the Shellstone Creek bedsareprobably40feet(12m)thickorless. AtShellstone Creek, the unit is less than 20 feet (6 m) thick but the composite thickness of the Shellstone Creek beds and residuuma few miles to the east (awayfrom the Ocmulgee River) may be more than 70 feet (23 m).
The environment of deposition of the Shellstone Creek beds was coastal marine and appears to have been sound-lagoonal. The depositional environment of the Shellstone Creek beds was probably similar to that of the Barnwell, based onlithologic similarity to the underlying Barnwell Group,
Age
A Clypeaster rogersi found in the bedded chert from the lower part of the Shellstone Creek locality (B. Carter,pers. com., 1988), and aRhycholampas gouldii found in chert from the stratigraphicallyhigher residuum 1mile (1.6 km) east of the Shellstone Creek locality indicates the age of the unit is Lower Oligocene, Vicksburgian. Based on stratigraphic position and the presence of the C. rogersi, the Shellstone Creek beds are probably correlative with the Mariannaand Glendon exposures near Hawkinsville, 12.5 miles (20 km) to the south (Pl. 1)(compare with Pickering, 1970, Pl. 1).

UNDIFFERENTIATED RESIDUUM
Definition
The name FlintRiver formation was proposed by Cooke(1935, p.1170-1171) fordepositsexposedabovethe Ocala Limestone 'along the Flint River between Hales Landingand Red Bluffnear Bainbridge inDecaturCounty, Georgia. The assortment of deposits exposed there included residuum; fossiliferous chert (with Oligocene fossils); Pleistocene fluvial deposits; and limestone. Because the chert contains Oligocene fossils, the "formation" was conceived to be of Oligocene age. The Flint River formation was subsequently mapped both as Flint River formation and Ocala Limestone by Cooke (1939, 1943), residuum and Suwannee Limestone by MacNeil (1947a), and Flint River formation and Neogene undifferentiated by Pickering (1970).
MacNeil (1944b, p. 35-37) abandoned the Flint Riverformationbecauseheapparentlyconsideredittobe an inappropriate stratigraphic unit:
The formation consists of fossiliferous chert, clay, sand, and gravel, intermingled and entirely without bedding. Recent mapping in southeastern Alabama by the writer has shown that the Flint River is not a single unit of deposition, but a mixture of the disarranged beds of Miocene formations. It was probably formed by the solution of rather pure Oligocene limestones during which partial silicification took place and higher beds of Tampa and Catahoula age were disarranged and incorporated with the limestone residuum by sink hole action.
MostworkershavefollowedMacNeil(1946,1947a,1947b) in abandoning the name Flint River formation althoug!1 Herrick and Counts (1968) and Pickering (1970) reintroduced the name.
I am in agreement with earlier authors that the Flint River formation is an invalid lithostratigraphic unit as proposed by Cooke (1935) and the name should not be used. However, the variably cherty, clayey residuum covers large areas of the Coastal Plain in Georgia (Fig. 9) and, although it consists of weathered deposits of Middle Eocene to Miocene age, the vast majority of the material appears to have l;>een derived from Oligocene marine deposits. Therefore, this residual material cannot be ignored in a stratigraphic study because it gives stratigraphic information on theoriginaldistributionand physical nature of the component deposits. In the present

25

study on the Oligocene stratigraphy of Georgia, the residual sediments described and discussed are only those that can be shown to be, or are believed to have been, derived from Oligocene marine deposits. This age relationship is based on the presence of associated cherts bearing Oligocene fossils, and on the direct physical correlation of chert-bearing residuum with residuum barren of fossiliferous chert that occurs nearby in a similar stratigraphic position and at similar elevations. It is admitted that due to the extreme disarrangement and dislocation of these sediments relative to the original deposits, the present physical relationship of the fossiliferous chert with the enclosing nonfossiliferous residual matrix is problematical; and the present fossiliferous chert may have a significantly different age from that of the enclosing, original undisturbed parent siliciclastic sediment (protolith). In addition, the time of generation of the residuum is much younger than the age of the unweathered parent deposits.
Lithology
Most of the Oligocene residuum consists of moderate reddish brown (10 R 4/6), variably sandy clay with associated blocks or inclusions of variably fossiliferous chert and local concentrations of ironstone. MacNeil (1944a, p. 4-5) gave an adequate description of these sediments:
The Flint River formation, an assortment of varicolored chert, clay, sand, and gravel covers very large areas in Georgia and eastern Alabama. It is heterogeneous and entirely without bedding. It results from the solution of rather pure Oligocene limestones during which partial silicification took place to form large blocks of chert, and higher beds of Tampa and Catahoula age were disarranged and incorporated with or settled on the limestone residuum and chert by sink hole action. In regions where the Ocala has been dissolved, the Flint River is frequently incorporated with the residuum of the Ocala by the same process. In some areas the Ocala limestone also formed chert, and Ocala and Oligocene cherts are mixed together. Locally, however, the Ocala settled more uniformly and its residuum is recognizable as a zone of compacted sand and crumpled shale below the Flint River.

Although both Cooke (1935, 1943) and MacNeil (1944a, 1944b) included gravel in the concept of the Flint River formation, it is my observation that the Oligocene deposits of the southeastern United States are devoid of quartz gravel and quartz pebbles. The gravel identified by Cooke (1935, 1943) and MacNeil (1944a, 1944b) occurs in high terrace, fluvial deposits of the Chattahoochee and Flint Rivers across the entire southern part of the Dougherty Plain and is stratigraphically unrelated to the Oligocene or Eocene residual deposits.
MacNeil (1944a, 1944b) indicated that the sand and clay in the residuum were emplaced during the weathering of the Oligocene carbonate deposits from overlying Miocene deposits. If this is so, and I have seen nothing in the field that is inconsistent with this interpretation, then the sand component of the Oligocene residuum is largely an artifact of post-Oligocene weathering conditions and is not a reflection of the original lithology of the Oligocene sediments. It is possible, however, that much of the Oligocene clay residuum in Georgia was derived from the weatheringand leaching of the Bucatunna Clay. The Bucatunna Clay originally may have occurred as far east as central Georgia.
Stratigraphic Relationships
The undifferentiated Oligocene residuum is known to occur in Georgia from the ChattahoocheeRiver area in the west to the vicinity of the Oconee River (Laurens County) in the east (Fig.10). Oligocene residuum has not been identified in outcrop east of the vicinity of the Oconee River except along Brier Creek in northernmost Screven County, Georgia.
The undifferentiated Oligocene residuum generally occurs at the tops of the sections north of Baker County, Georgia. :South of the vicinity of Baker County, the Oligocene residuum contains both Oligocene and Eocene cherts. North of the Dougherty Plain, the Oligocene residuum also directly overlies the Lisbon Formation and Factory Creek Formation of Huddlestun and others (in review). In Pulaski, Bleckley, and Laurens Counties, the Oligocene residuum overlies the Ocmulgee Formation and it is possible that in the far updip reaches of the deposit, the residuum directly overlies the Tobacco Road Sand. Also, in parts of Pulaski, Bleckley, and Laurens Counties, the undifferentiated Oligocene residuum is overlain by either Hawthorne Group deposits or Altamaha Formation.
In Burke County, Georgia, where the Tobacco Road Sand has been deeply weathered and resembles the typical Eocene-Oligocene residuum, it is possible that the Tobacco Road can be distinguished from Oligocene residuumbecause the sandsof the Tobacco Road are coarser and poorly sorted. In southwestern Georgia, where the residuum may be a mixture of deeply weathered Eocene,

26

N
t
.. -

Gulf of Mexico

DIXIE

0 10 20 30 40 50 miles
E3 E3 H

l.

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Figure 10. The areal distribution of undifferentiated Oligocene residuum in Georgia. 27

Oligocene, and Miocene sediments, the above distinction would not be true.
Deeply weathered and residual sediments of the Altamaha Formation can be distinguished from Eocene and Oligocene residuum in that the Altamaha is mottled (gray, maroon, and orange), containsno chert or fossils, is feldspathic, and the sand is generally medium to coarse and poorly sorted.
The thickness distribution of the Oligocene residuum is very irregular due to its residual nature. It appears to average approximately 50 feet (15m) thick but locally it may be more than 100 feet (30 m) thick.
Age
Based on publishedfaunallists(Dall,1916;Cooke, 1923, 1943; Mansfield, 1937, 1940), the undifferentiated Oligocene residuum includes both lower Oligocene, Vicksburgian (Rupelian) and Upper Oligocene, Chickasawhayan (Chattian) components. According to M.E. Hunter (written com., 1992), however:
The residual clays overlying the pinnacled upper contact of the Bridgeboro Limestone at its type locality in Mitchell County, Georgia, contain silicified molluscan fossils that include such taxa as Orthaulax herrumdoensis, Ampullina flintensis and other species. In addition to the Bridgeboro pit, a small fossil assemblage that includes these and a number of other fossil species also occurs locally above the Suwannee Limestone (post-Suwannee of Yon and Hendry, 1972) in parts of peninsular Florida and in the Oligocene residuum near the Flint River, and westward near the Florida state line as far west as Geneva, Alabama. I feel reasonably confidant in suggesting a correlation between these three areas. However, none of these taxa seems to have been reported from the type Chickasawhayan in Mississippi and I have found none of the typical Chickasawhayan fossils in the Florida/Georgia localities discussed above.
I therefore question the old, long standing correlations (established by Cooke,1923;1935;1943;and Mansfield, 1937; 1940) in which the three Florida/Georgia areas were

correlated with the type Chickasawhayan of Mississippi.
Therefore the precise ages of this Florida Bank, Oligocene, molluscan fauna are not established in terms of the type provincial section in Mississippi.
GULF TROUGH STRATIGRAPHIC ASSOCIATION
OCHLOCKONEE FORMATION, new name
Definition
The Ochlockonee Formation is named here for a finely granular to lutitic, variably dolomitic, microfossiliferous limestone that is restricted to the subsurface in the Gulf Trough of southwestern Georgia and the eastern panhandle of Florida. In Gadsden County, Florida, the lower part of the Ochlockonee Formation of this report was included in the Tallahassee limestone by Applin and Applin (1944), and the upper part was included in the Gadsden limestone by Moore (1955). The Ochlockonee Formation has been variously included in theOcala Limestone,Lisbon Formation, Claiborne Group (undifferentiated), and Oligocene and upper Eocene (undifferentiated) inThomasand ColquittCounties,Georgia, by Herrick (1961, p. 402, 128-133); in the Marianna Limestone by Sever and Herrick(1961, p.402,128-133);in the MariannaLimestone equivalentbyZimmerman (1977, p. 16), in the Ocala Limestone by Puri and Vernon (1964, p. 94-96), and in the Suwannee Limestone by Gelbaum and Howell (1982, p. 143-147). In the Gulf Trough, the Byram Formation of Zimmerman (1977, p. 17) is largely the upper dolostone section of the Ochlockonee Formation and probably Wolf Pit Dolostone.
The name Tallahassee limestone of Applin and Applin (1944) is not reintroduced as a name for this formation because no type well was ever designated for the proposed formation and the Tallahassee limestone as described and applied by Applin and Applin (1944) is stratigraphically inconsistent. For example, Applin and Applin (1944) considered the Tallahassee limestone to be middle Eocene (Claibornian) in age. InJeffersonCounty, Florida, and in Decatur County, Georgia, the Tallahassee limestone of their usage does underlie the Ocala Limestone. However, Applin and Applin (1944, p. 1736) identified the Tallahassee limestone in the Florida Geological Survey well W-4 in Gadsden County, Florida, where it is Early Oligocene (Vicksburgian) in age. Therefore, the name Tallahassee limestone would require unreasonable redefinition and revision, and would be different in content from the original intended use of the formation name.
The name Gadsden limestone was introduced by

28

Moore (1955, p. 43) for:
...those limestones of Jackson age that have no, or few, specimens of the larger Foraminifera such as Lepidocyclina, Asterocyclina or Operculinoides. The type section of the Gadsden limestone occurs in the Florida Geological Survey well W-4, from Quincy, Gadsden County, Florida, between the depths of 680 feet and, "tentatively'', 900 feet. In the well W-4, the Gadsden limestone overlies the Tallahassee limestone of Applin and Applin (1944) at a depth of 910 feet although, "a clear-cut bottom for the Gadsden limestone could not be located in this well.
Moore (1955, p. 44) considered the Gadsden limestone to be Late Eocene in age, and correlative with the Ocala Limestone. He considered the Gadsden and Ocala Limestones in Jackson County, Florida, to be separated by a normal fault (Cypress fault) with the Gadsden limestone occurring on the downthrown side of the fault.
Purl and Vernon (1964, p. 95) rejected the name Gadsden limestone and the concept of the formation:
Because the stratigraphic unit Crystal River Formation was established to include all calcareous sediments lying between the Williston Formation and the overlying Oligocene limestones (Purl, 1953), the downdip sediments are referred in this paper to the Crystal River Formation.
The Gadsden limestone of Moore (1955) was thereafter included in the Crystal River Formation because it was believed to be Late Eocene in age.
The Gadsden Limestone is not reintroduced in this report because it would take major revision and expansion of the original concept of the formation, and the revised and expanded formation would differ significantly inconcept and content from the original definition of the formation. Both the Tallahassee limestone of Applin and Applin (1944) and the Gadsden limestone of Moore (1955) are subsumed under the Ochlockonee Formation of this report in Gadsden County, Florida. The Ochlockonee Formation is Early Oligocene whereas the Tallahassee limestone (lower part of the Ochlockonee Formation) in Gadsden County~ Florida, was postulated to be Middle Eocene (Claibornian) by Applin and Applin (1944), and the Gadsden limestone (upper part of the

Ochlockonee Formation) was postulated to be Upper Eocene (Jacksonian) by Moore (1955). Both the lower and upper parts of the Ochlockonee Formation in theW4 are Oligocene.
One formal member of the Ochlockonee Formation is recognized in this report, the Pridgen Limestone Member of the Ochlockonee Formation. The Pridgen Limestone Member is restricted in occurrence to the Gulf Trough northeast of the Chattahoochee Embayment whereas typical Ochlockonee Formation is known to occur only in the Chattahoochee Embayment.
The modifying term of the Ochlockonee is "formation" rather than "limestone" because large parts of the Ochlockonee section at various sites in southwestern Georgia have been extensively dolomitized. In Florida and ColquittCounty, Georgia, however, the Ochlockonee Formation appears to consist largely of limestone with extensive dolomitization only in the upper part of the formation.
Type Section
The name Ochlockonee is taken from the Ochlockonee River which lies 1 mile (1.6 km) southwest of the type locality. The type locality of the Ochlockonee Formation consists of two cores taken less than 200 feet (61 m) apart near the bank of a farm pond, approximately 3.1 miles (5.0 km) northwest of Moultrie, Colquitt County, Georgia (Fig. 11). The type section or unitstratotype (composite holostratotype) of the upper part of the formation occurs from 606 feet to T.D. at 790 feet in the core Colquitt 5 (GGS-3199, U.S. Gypsum core 768)(Figs. 12 and 13). The unit-stratotype (holostratotype of the lower part of the formation) occurs from 790 feet to 976 feet in the core Colquitt 9 (GG5-3535) (Fig. 13). The upper boundary stratotype of the Ochlockonee Formation occurs at 606 feet in the core Colquitt 5 (GG5-3199) where the Ochlockonee is overlain with apparent conformity by the Wolf Pit Dolostone The lower boundary stratotype of the Ochlockonee Formation occurs at 976 feet in the core Colquitt 9 (GGS-3535) where the Ochlockonee Formation overlies, with apparent disconformity, undifferentiated Upper Eocene limestone. The two cores, the Colquitt 5 (GG5-3199) and the Colquitt 9 (GG5-3535) are stored at the Georgia Geologic Survey in Atlanta, Georgia.
Lithology
The Ochlockonee Formation is typically a light olive gray (5 Y 5/2) to yellowish gray (5 Y 7/2), hard and tough, variably recrystallized, massive-bedded to thinly bedded, bioturbated and burrowed, finely to very finely granular, even-textured, somewhat argillaceous limestone that is variably dolomitic and contains scattered

29

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The type locality of the Ochlockonee Formation (Colquitt 5 and 9), Wolf Pit Dolostone (Colquitt 5), and Okapilco Limestone (Colquitt 5) (U.S. Geological Survey, Moultrie, Ga. 1:24,000 topographic quadrangle).

30

~Limestone

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Lithology symbols.

31

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The measured holostratotype of the Ochlockonee Formation. 32

dolostone intervals. The dominant lithic component of the formation is limestone; subordinate lithic components include dolomite and dolostone, clay, chert, pyrite, phosphate, glauconite, microfossils, very minor and scattered mica and fine-grained sand, and scattered occurrences of gypsum.
The limestone (and all but the most intensely dolomitized intervals) is finely granular and the calcareous particles, where visible, are roughlyequidimensional. The grain size of the calcareous particles ranges from medium sand to silt. In the coarser grained intervals, the calcareous grains appear to be suspended in a finer grained matrix. The textural variation within the sediment appears to result from incomplete mixing of fine, nondescript lutitic material and granular calcitic material. Typically, the calcareous sediment is bioturbated and burrowed; the sediment is incompletely mixed and displays color marbling. In some intervals, however, especially the fine-grained, chalky, nongranular intervals, the sediments show no evidence ofbioturbation and are massive-bedded and devoid of sedimentary and biogenic structures. The thinly bedded to laminated sediments of the Ochlockonee Formation generally are argillaceous and have the appearance of calcareous shale. Rarely there are beds thatconsistoflaminated or massive and structureless calcareous clay. The only other sedimentary structures that have been observed consist of rare occurrences of limestone and dolostone intraclasts.
Dolomitization has generally affected parts of any given section of the Ochlockonee Formation. Beds of dolostone or dolomitic limestone are most prevalent in the upper part of the formation and the Ochlockonee Formation generally grades up-section into dolostone. Dolostone and dolomite, on the other hand, are not known to occur in the lowest part of the formation. The Ochlockonee Formation hasbeenextensivelydolomitized in Grady and Decatur Counties, Georgia. Dolomite occurs both as scattered dolomite rhombs in limestone and as light yellowish brown (10R6/4-10R6/2) to olive gray to brownish black (5y4/1-5Y2/1-5YR2/1) sucrosic dolostone.
Chert concretions and, less commonly, calcite concretionsoccurat scattered intervalsin the Ochlockonee Formation. Glauconite is typically rare and phosphate is known to occur only in the basal bed of the formation. Finemica is present in some ofthe argillaceous beds of the Ochlockonee and fine- to very fine grained quartz sand also occurs rarely and in trace amounts. Minor finely disseminated pyrite commonly is present.
Except for some of the more argillaceous intervals, the OchlockoneeFormationischaracteristicallytough and indurated to some degree. The typical poor preservation of foraminifera indicates recrystallization of the limestone. However, it is only inthe dolomitized intervals that recrystallization is generally evident.

The Ochlockonee Formation is not macrofossiliferous but microfossils, and especially foraminifera, are common and locally abundant. Due to induration and recrystallization, it is possible to concentratemicrofossilsonlyfromscattered thin intervals. Where the limestone hasbeen extensivelyrecrystallized or indurated, the limestone (or dolostone) appears in hand specimens and under low magnification to be completely nonfossiliferous.
Stratigraphic Relationships
The Ochlockonee Formation is restricted to the Gulf Trough in Florida and Georgia (Fig. 14). Typical Ochlockonee Formation does not occur northeast of Colquitt County, but grades laterally northeastward into the argillaceous, more coarselycalcarenitic Pridgen LimestoneMember. Th~ Ochlockonee Formation is notknown to occur northeastof Jeff Davis County, Georgia, and it is known to be present in the central part of the Chattahoochee Embayment in Florida. However, it possibly underlies all of the embaymentto the south as far as the coastal area (Fig. 14).
In Georgia, the Ochlockonee Formation disconformably overlies undifferentiated Upper Eocene (Jacksonian) limestone and is overlain with apparent conformity by the Wolf Pit Dolostone, both of which are restricted in occurrence to the Gulf. Trough. In the Chattahoochee Embayment in Florida, the Ochlockonee Formation does not appear to be overlain by the Wolf Pit Dolostone but rather by a correlative, undifferentiated limestone.
In contrast to the Ochlockonee Formation, the underlying Jacksonian limestone in the Gulf Trough consists of slightly glauconitic, fine-grained, more lithologicallyvariable limestone. The Wolf Pit Dolostone is distinguished from the dolomitized Ochlockonee Formation in the more complete dolomitization of the section, commonly with the loss of all primary sedimentary structures. The overlying Oligocene limestones are more coarsely granular/porous, macrofossiliferous and, in the inner embayment and northeastern part of the Gulf Trough, are typically coral-rich (Okapilco Limestone). The stratigraphically correlative Bridgeboro Limestone on the flanks of the,Gulf Trough is distinguished by an abundance of rhodoliths (hard, concentrically layered, irregularly rounded, calcitic balls formed by red algae [Bosellini and Ginsburg, 1971; Manker and Carter, 1987]) and is variably rnacrofossiliferous and fine- to coarsegrained with common bioclastic texture.
Because of poor stratigraphic control in the Chattahoochee Embayment in southwestern Georgia, little can be said. of the thickness distribution of the Ochlockonee Formation based on direct measurements in cores and wells. However, in the cores Colquitt 5 and

33

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of Mexico
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Figure 14.

The areal distribution (subcrop) of the Ochlockonee Formation in Georgia and northern Florida.

34

Colquitt11 (GGS-3199 and GGS-3535)in Colquitt County, Georgia, the composite thickness of the Ochlockonee Formation is 374 feet (114m). Well data indicate that the Ochlockonee Formation thickens southwestward into the Chattahoochee Embayment; it is at least 705 feet (215 m) thick in the Florida Geological Survey well W-4, and may be more than 1200 feet (366m) thick in the well W6217 in Gadsden County,Florida.
The Ochlockonee Formation was deposited in a relatively deep-water channel whose water depth initially may have been much as 700 or 800 feet (213 or 249 m) in Georgia and significantly deeper in Florida. Deposition of the Ochlockonee was a trough-filling event and the carbonates deposited late in the depositional history of the formation were probably deposited in significantly shallower water. The low diversity of the benthic foraminiferal assemblagesmay suggesta somewhatrestricted bottom environment, or may possibly be the result of selective destruction of foraminiferal tests during mild to severe recrystallization.

more microfossiliferous part of the formation. The planktonic foraminifera identified from the
Ochlockonee Formation include the following:
Globorotalia increbescens Globigerina ampliapertura G. eocaena
This association, in the absence of Globorotalia cerroazulensis, Hantkenina spp., and Cribrohantkenina inflata is indicative of anEarlyOligocene(orpossiblylatest,LateEocene)age,and would be included in the Cassigerinella chipolensisPseudohastigerina micra Zone ofStainforthand others (1975), andinZon~P17-P19ofBlow(1969),(Pl.l). In terms of the provincial chronostratigraphy, the precedingassociation is compatible only with the Vicksburgian. Therefore, the planktonic foraminifera support the age assigned to the Ochlockonee Formation based on the Early Oligocene (Vicksburgian) benthic foraminifera.

Age
The following benthic foraminifera have been identified from the Ochlockonee Formation:

PRIDGEN LIMESTONE MEMBER OF OCHLOCKONEE FORMATION, new name
Definition

THE

Lenticulina vicksburgensis Lenticulina spp. Eponides byramensis E. obesus Siphonina advena Baggina xenoula Planulina cocoaensis Cibicidoides cookei C. pippeni Anomalinoides bilateralis Bulimina sculptilis Uvigerina cf.jacksonensis U. cf. cocoaensis U. vicksburgensis U.glabrans
This association is similar to that of the Lower Oligocene Red Bluff Clay and Marianna Limestone of southeasternMississippi and southwestemAlabarna and many of the species are not known to range below the Oligocene (compare with Bandy, 1949; Deboo, 1965). Moore (1955, p. 33) identified Bolivina caelata and B. byramensis from the Gadsden limestone (=upper part of the Ochlockonee Formation) in Jackson County, Florida. Neither species has been reported from deposits older than Oligocene. Therefore, the benthic foraminifera support an earliest Vicksburgian age for at least the lower,

The Pridgen Limestone Member of the Ochlockonee Formation is named herein for a limestone subdivision of the Ochlockonee Formation that is restricted in occurrence to the northeastern, parallel sided part of the Gulf Trough. E. R. Applin (1960) briefly discussed this unit from the oil test well GGS-509 (Fig. 15) in Coffee County, Georgia. She did not assign a stratigraphic name to the Oligocene section in the well. Much of her discussion concerned the larger foraminifera Miogypsina gunteri and Miogypsina antillea and the beds that contain them in the test well. These beds, however, are included in the Lower MioceneParachucla Formation ofAquitanianage(Huddlestun, 1988). ApplinandApplin (1964) described a composite section from three more test wells (GGS-468, GGS-508, GGS-509) from this area in Coffee County (Pridgen prospect) in which they referred to the Pridgen Limestone Member of this report, the Wolf Pit Dolostone, the Okapilco Limestone, and the overlying Parachucla Formation as Oligocene Series undifferentiated. GelbaumandHowell (1982, p.143-147) referred to this unit as Suwannee Limestone, and McFadden and others (1986) referred to it as Oligocene undifferentiated.
The modifying term of the Pridgen Member is "limestone" rather than strictly "member'' because the known lithology of the unit is overwhelmingly dominated by limestone. Dolostone or clay occurs only in

35

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The type locality of the Pridgen Limestone Member of the Ochlockonee Formation, reference locality of the Okapilco Limestone and Wolf Pit Dolostone, and locations of oil test wells of the Pridgen Prospect of Applin (1960) (U.S. Geological Survey, Broxton North, Ga., 1:24,000 topographic
quadrangle)

36

scattered beds or disseminated within the limestone.
Type Section
The name Pridgen is taken from the community of Pridgen in northern Coffee County, Georgia. The type locality of the Pridgen Limestone Member is the core site of the Coffee 4 (GG5-3541)(Fig. 15), located approximately 1.7 airline miles (2.7 km) northeast of the community of Pridgen). The type section or unit-stratotype (holostratotype) of the member occurs in the interval700 feet to 992 feet in the core (Fig. 16). The upper boundary stratotype of the Pridgen Limestone Member occurs at approximately 700 feet where the Pridgen Limestone is conformably and gradationally overlain by the Wolf Pit Dolostone. The lower boundary stratotype of the Pridgen Limestone occurs at 992 feet in the core where an upper dolostone bed ofthe undifferentiated Upper Eocene limestone unit is gradationally overlain by the Pridgen Limestone Member. The type core is stored at the Georgia Geologic Survey in Atlanta, Georgia.
The core Berrien 10 (GG5-3542) is here designated a reference sectionand parastratotype ofthe Pridgen Limestone Member of the Ochlockonee Formation. The coresiteofthe Berrien 10 (GGS-3542) isapproximately2.1 airline miles (3.4 km) northeast of the village ofEnigma in northwestern Berrien County, Georgia (Fig. 2). The Pridgen Limestone Member occurs in the interval721 feet (above which is a core gap) to 977 feet. The Pridgen Limestone grades downward into a five feetthick, calcareous clay bed in this core. The undifferentiated Upper Eocene limestone conformably underlies the clay bed, giving the appearance of continuous deposition across the stage boundary. The reference core is stored at the Georgia Geologic Survey in Atlanta, Georgia. At this time, undisturbed Pridgen Limestone can be examined in only the two cores, the Coffee 4 (GG5-3541) and the Berrien 10 (GGS-3542).
Lithology
Based on the lithology of the Pridgen Limestone Member of the cores Coffee 4 (GGS-3541) and Berrien 10 (GGS-3542), the unit consists of variably argillaceous, variably dolomitic limestone with scattered beds of dolostone and laminated clay. It is finely to coarsely granular, weakly fossiliferous limestone. The Pridgen Limestone is generally massive and structureless. However there are appreciable sections in the formation that are distinctly stratified. Scattered beds of dolostone are more common in the upper part of the formation and laminated clay is more common in the lower part. The dominant lithic component of the Pridgen Limestone Member is limestone; minor to trace components of the lithology include dolomite, dolostone, clay, carbonaceous

material, pyrite, glauconite, phosphate, fossils, and rare and scattered very fine grained sand.
The Pridgen Limestone generally is hard, tough, and variably recrystallized. It is rarely soft and unconsolidated. Beddingtypicallyis thick where the sediments are massive and devoid of biogenic and sedimentary structures. Less commonly the stratification is mediumto thin-bedded or laminated. Some bioturbated and burrowed intervals also are present. The texture of the sediment typically is finely to coarsely granular but beds ofveryfine grained, chalky limestone are not uncommon. The texture also ranges from even-textured to finely bioclastic and rough-textured. A consistent occurrence of carbonaceous material along bedding planes with some scattered sea grass impressions also appears to be characteristic of the member. The Pridgen Limestone is variably fossiliferous with both nonfossiliferous beds and beds containing commonly occurring larger and smaller foraminifera and less commonly occurring small macrofossils (especially bryozoa).
The lithology of the Pridgen Limestone Member is similar to that of the typical Ochlockonee Formation in that it is granular and calcarenitic, generally thick-bedded and massive, argillaceous, dolomitic, microfossiliferous, and not coarsely macrofossiliferous. The physical features that distinguish the Pridgen Limestone from typical Ochlockonee Formation are as follows: in general the Pridgen Limestone shows more stratification, is more coarsely textured with finely bioclastic intervals, more macrofossiliferous with a consistent occurrence of larger foraminifera (the characteristic "deepwater" foraminiferal fauna of the typical Ochlockonee Formation does not appear to be present in this unit), chalkier, more argillaceous with more discrete beds of clay, more carbonaceous, and less dolomitic.
Stratigraphic Relationships
The Pridgen Limestone Member of the Ochlockonee Formation is restricted to the Gulf Trough in Georgia, from the vicinity of Coffee County in the northeast to the vicinity of Tift County in the southwest (Fig. 17). The Pridgen Limestone grades laterally southwestward into typical Ochlockonee Formation in southwestern Tift or northeastern Colquitt Counties. Northeast of Coffee County, the Pridgen Limestone Member eithergradeslaterallynortheastward into undifferentiated calcareous sand and sandy limestone (based on well cuttings) or it pinches out. The upper part of the Pridgen Limestone Member occurs in the same stratigraphic position as the Suwannee Limestone on the flanks of the Gulf Trough to the south and the lower part occurs in the same stratigraphic position as the Bridgeboro Limestone on the flanks to the north. I assume, therefore, that the Pridgen grades laterally on the flanks of the trough into

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and parastratotype of the Wolf Pit Dolostone.



38

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39

the Bridgeboro and Suwannee Limestones. However, there is no stratigraphic information from the south flank of the trough and it is not known whether the Pridgen Limestone pinches out or grades into another formation.
The Pridgen Limestone Member either abruptly or gradationally overlies undifferentiated upper Eocene limestone, and is overlain conformably by the Wolf Pit Dolostone in the type core. The Pridgen Limestone Member of the Ochlockonee Formation is 317 feet (97 m) thick in the core Coffee 4 (GGS-3541) and is 256 feet (78 m) thick in the core Berrien 10 (GGS-3542).
Age
Based on physical correlation with the Ochlockonee Formation, the Pridgen Limestone Member is Early Oligocene, Vicksburgian (Rupelian) in age (Pl. 1). Compatible with this age, foraminifera that have been reported from this unit include the following:
Lepidocyclina undosa Nummulites panamensis Dictyoconus cookei D. floridanus Pararotalia mexicana
The known foraminiferal fauna of the Pridgen Limestone Member of the Ochlockonee Formation presents an anomaly and is difficult to reconcile with the stratigraphic model of the Gulf Trough as presented in this report. The Pridgen Limestone must have been deposited in relatively deep water below the photic zone (i.e., that part of the water column illuminated by sunlight). However, I have recovered no deep-water benthic foraminifera from the unit such as are found in typical Ochlockonee Formation. The small carbonaceous content of the unit, the presence of what appears to be sea grass impressions, the common occurrence of relatively shallowwater smaller and larger foraminifera, especially
Dictyoconus cookei, D. floridanus, Lepidocyclina, and Nummulites are all suggestive of a shallow to very shal-
low water marine environment. This would suggest that much shallow water material was able to reach the bottom of the eastern part of the Gulf Trough during deposition of the member. Also the presence of thinly bedded limestone indicates that from time to time, the bottom of the trough was not inhabited by a burrowing infauna. It is possible that the bottom conditions and water-mass conditions in the Gulf Trough at the time of deposition of the Pridgen Limestone deviated appreciably from normal marine conditions, consequently affecting the composition and distribution of the benthic fauna.
The occurrence of Dictyoconus cookei and D. floridanus in the lower part of the Pridgen Limestone in
Coffee County is especially perplexing. Applin (1964)

reported D. cookei and D. floridanus from the GGS-509 in Coffee County. Dictyoconus cookei is also present in the
same stratigraphic interval in the Coffee 4 (GGS-3541) taken approximately 0.1 mile (0.06 km) from the GGS-509
(Fig. 14). Therefore, the occurrence of Dictyoconus in the
lower part of the Pridgen Limestone in the Gulf Trough
cannot be due to contamination. Dictyoconus was a com-
mon component of the Tethyan and Florida Bank faunal association through the Cretaceous to Middle Eocene and is characteristic of extremely shallow water, carbonate banks environments. It evidently flourished in water masses that deviated considerably from normal, openocean, marine water masses. The genus became extinct worldwide at the end of the Middle Eocene except somewhere in vicinity of the Florida Bank where it survived in refugia(comparewithStubbs, 1941, p.14;andCole, 1941, p. 15-16). I have neither seen nor know of any reports of
Dictyoconus occurringin sedimentsbetween the top of the
Claibornian Avon Park Formation (and the Inglis Formation of Vernon [1951] and Purl [1957]) on the Florida Bank and the lateVicksburgian Suwannee Limestone. Considering the open-marine environment that generally prevailed within the Suwannee Strait during this span of time (Middle Eocene through earliest Oligocene), the presence of the Florida Bank foraminiferal fauna in the strait would appear to be most unlikely.
The Florida Bank environment invaded the SuwanneeStraitbrieflyonlyduringtheSuwannee-Byram stand of the sea and the only occurrence I know of
Dictyoconus after the Avon Park and Inglis is in the
Suwannee Limestone. Therefore I would expect that if
Dictyoconus were found inGulfTrough deposits, it would
have been reworked from its very shallow habitat on the flanks of the trough and carried into deep water through submarine slump or down slope movement of shallow water sediments during the deposition of the Suwannee Limestone. Deposits within the Gulf Trough containing
Dictyoconus then should be correlative with the Suwannee
Limestone. However, the stratigraphicmodelconstructed in this report would indicate that the lower part of the Ochlockonee Formation (and the Pridgen Limestone Member) is earlyVicksburgian in age. Ifthe lower part of the PridgenLimestonecontainsDictyoconus thenit would have been derived from shelf deposits on the upper flanks ofthe trough during theearlyVicksburgian. How-
ever, Dictyoconus is not known to occur in early
Vicksburgian shelf or carbonate bank deposits in the Suwannee Strait or elsewhere.
If it is concluded that Dictyoconus was derived
from the Suwannee Limestone on the upper flanks of the Gulf Trough, then the entire Pridgen Limestone is Suwannee-equivalentandcorrelativeonlywith theByram Formation of the Vicksburg Group. Itwould also appear that through physical correlation southwestward down the trough, that the lower partof the typical Ochlockonee

40

Formation in Colquitt County would also be correlative with the Suwannee Limestone and Byram Formation. This is an extreme interpretation and would indicate that the stratigraphic framework of the Gulf Trough and the Oligocene history of the Suwannee Current is more complex than described in the simple model proposed in this report.
A similar and possibly related example of an anomalous occurrence of the Florida Bank , Tethyan (Caribbean) foraminiferal fauna was reported by Applin and Applin (1964, p. 120-123) in the well GG5-55 located in northwestern Decatur County, Georgia. In this case, Dictyoconus floridanus, Valvulina sp., and Valvulammina sp. were identified at the top of the Middle Eocene (Avon Park Limestone of Applin and Applin, 1964). The top of the Middle Eocene in the nearby GG5-57 is 76 feet lower than that in the GG5-55 and contains no Florida Bank (Tethyan) , Claibornian foraminiferal fauna but rather a normal, Middle Eocene foraminiferal fauna. The sites of the GG5-55 and GG5-57 are on or near the northern flank of the Gulf Trough where no foraminifera peculiar to the Florida Bank (Tethyan) environment had been previously or subsequently reported. If the Middle Eocene Florida Bank (Tethyan) foraminifera reported from the GG5-55 are indeed in place, then perhapsthere were many small and temporally changing sites of refugia in and south of the Suwannee Strait during the Middle Eocene (Claibornian), Late Eocene (Jacksonian) through Early Oligocene (Vicksburgian). Few of these sites are preserved in the stratigraphic record because they would have been small, localized, and bathyrnetrically high (very shallow water) and, consequently, were sites of nondeposition or were susceptible to subsequent erosion and destruction.
Finally, in regard to the anomalous occurrence of the Dictyoconus cookei and D. floridanus in the Pridgen Limestone in the Gulf Trough in Coffee County, there is a small area on the southern flank of the Gulf Trough in Coffee County where the Miocene directly overlies the Ocala Limestone and the Oligocene is absent. It is conceivable that this area of absent Oligocene was in extremely shallow water during the Oligocene and no Oligocene sediments were deposited there. If so, this Oligocene bathymetric high could have served as a local refugium for the Florida Bank, Tethyan (Caribbean) benthic foraminiferal fauna within the Suwannee Strait. As such it may have been the source of the Dictyoconus present nearby in the Gulf Trough.
WOLF PIT DOLOSTONE, new name
Definition
The Wolf Pit Dolostone is named here for a dolostone formation that is confined to the Gulf Trough

in Georgia. It gradationally overlies the Ochlockonee Formation and is abruptly overlainby the Okapilco Limestone. The Wolf Pit Dolostone has been identified in two cores in the GulfTrough: in the type core Colquitt 5 (GG53199) in Colquitt County, and in the Coffee 4 (GG5-3541) in Coffee County. It was not cored in the Berrien 10 (GG53542) because that stratigraphic interval was drilled and casing set without having taken cores or well-cuttings. The Wolf Pit Dolostone is lithologically similar to the Suwannacoochee Dolostone that occurs at higher elevations on the continental shelf south of the Gulf Trough. It is similarly interpreted to have been deposited during a low stand of the sea when the sea was confined to the Gulf Trough. This low stand of the sea was lower than that of the Suwannacoochee low stand and first exposed the floor of the trough to very shallow water conditions.
Type Section
The name Wolf Pit is taken from Wolf Pit Branch, a small tributary of the Ochlockonee river whose confluence with the river is 1.4 miles (2.5 krn) northwest of the type locality. The type locality of the Wolf Pit Dolostone is the site of the core Colquitt 5 (GG5-3199), located adjacent to a small farm pond roughly 3.1 miles (5.0km)northwestofthecourthouseinMoultrie,Colquitt County, Georgia (Fig. 11). The type section, or unitstratotype (holostratotype) of the Wolf Pit Dolostone occurs in the interval 535 to 606 feet (Fig. 13)(also see McFadden and others, 1986, p. 206). The interval606 to 619 feet is broadly gradational with the underlying Ochlockonee Formation. The upper contact of the Wolf Pit Dolostone with the overlying Okapilco Limestone is abrupt and has the appearance of a disconformity.
The core Coffee 4 (GG5-3541) is designated here a reference localityand reference section (parastratotype) of the Wolf Pit Dolostone. The reference section of the. Wolf Pit occurs in the interval675 to 700 feet (Fig. 15)(also see McFadden and others, 1986, p. 168). The lower contact of the formation appears abruptly gradational with the underlying Pridgen Limestone Member of the Ochlockonee Formation. The upper contact appears tobe abrupt with the overlying, poorly recovered Okapilco Limestone.
Lithology
The lithology of the Wolf Pit Dolostone is a sucrosic, tan to brown dolostone. There are few other lithic components of the formation. Minor calcitic intervals occur in both cores and the basal Wolf Pit in the type core is slightly glauconitic. There are zones of selenite (gypsum) in the dolostone in the upper part of the formation in the type core but none is apparent in the Coffee County core. Similarly, there is minor pyrite in the basal

41

part of the formation in the type core and there is minor carbonaceous material in the basal part of the formation in the Coffee County core.
A dolostone section in the well GGS-962 (Sever and Herrick, 1967, p. 50,51) in the interval490 to 670 feet (called Byram Formation by Sever and Herrick, 1967) is tentatively assigned to the Wolf Pit Dolostone of this report. Sever and Herrick (1967) identified a green clayin residue of the dolostone and they thought the clay occurred within the dolomite rhombohedrons because no clay minerals were apparent in the untreated cuttings.
Most of the Wolf Pit Dolostone is sporadically fossiliferous above 602 feet in the type core with intervals that contain partially obliterated molds of Lepidocycliru~,
Nummulites, corals, bryozoans, and mollusks. Other in-
tervals are nonfossiliferous but contain still visible remnants of bioturbation and burrows indicating the environment of deposition was intermediate to that of the overlying Okapilco Limestone and the underlying Ochlockonee Formation in the inner Chattahoochee Embayment. No fossils are apparentin the Coffee County core and Sever and Herrick'(1967) reported the dolostone interval in the GGS-962 tci be barren of fossils.
The texture of the dolostone ranges from finely to coarsely sucrosic and the color ranges from buff to tan to brown..The degree of consolidation ranges from friable to thoroughly recrystallized, hard, and dense. In much of the dolostone, however, there is appreciable secondary porosity. In the Coffee County core, the lower part of the Wolf Pit Dolostone is thinly bedded and has a shaley appearance but no clay material is apparent in the core. Also, there is some minor amount of carbonaceous material in the Coffee County core that is not apparent in the type core. However, the interval below 607 feet in the type core contains a trace of pyrite. The basal part of the Wolf Pit in both cores appears to have been mo~t environmentally restricted with irregular mixed inclusions (intraclasts?) and calcite-filled veins or fractures between 603 and 606 feet in the type core, and "shaley'' dolostone with carbonaceous material in the Coffee County core.
In general, the lithology and sequence of lithologies of the Wolf Pit Dolostone are very similar to that of the Suwannacoochee Dolostone, with which the Wolf Pit was initially correlated by myself. However, the stratigraphic positions and elevations of the two dolostone formations indicate noncorrelation.
Stratigraphic Relationships
The Wolf Pit Dolostone is confined to the Gulf Trough from at least Colquitt County in the southwest to Coffee County in the northeast (Fig. 18). It probably extends farther in each direction. The test well GGS-962 drilled in Cairo, Grady County, Georgia (Sever and Herrick, 1967, p. 50-53; McFadden and others, 1986, p.

241-243), contains a dolostone in the stratigraphic position of the Wolf Pit and is tentatively identified as the Wolf Pit Dolostone. The limestone section below 670 feet in the GGS-962 that Sever and Herrick (1967) called Marianna Limestone is the Ochlockonee Formation of this report, and the fauna listed from that unit in the test well is the typical Ochlockonee deep water foraminiferal fauna. The limestone at the top of the Oligocene section in the Cairo test well, between471 and 490 feet, that Sever and Herrick (1967) called Suwannee Limestone, occurs in the stratigraphic position ofthe Okapilco Limestone. The lithology of this limestone, however, is not Suwannee lithology, and it also lacks the colonial corals that are characteristic of the Okapilco Limestone. It appears that the Okapilco Limestone grades laterally southwestward into a deeper water limestone where colonial corals did not flourish. This upper limestone of the Cairo test well is unusually thin and the underlying dolostone unusually thick, suggesting that dolomitization also occurred above the Wolf Pit Dolostone in the lower part of the overlying limestone formation. The southwestern limit of the Wolf Pit Dolostone is not known. Dolostone overlying the Ochlockonee Formation has not been reported in the W-4 well in Quincy, Gadsden County, Florida (Applin and Applin, 1944; Moore, 1955) or from Jackson County, Florida (Moore, 1955). The Florida Geological Survey core (W-6901) at Alum Bluff in Liberty County, Florida, did not penetrate to the projected depth of the Wolf Pit Dolostone (Pl. 2). The Wolf Pit Dolostone is 71 feet (22 m) thick in the type core Colquitt 5 (GGS3199) and is 25 feet (7.6 m) thick in the reference core Coffee 4 (GGS-3541).
The Wolf Pit Dolostone seems to have been deposited during an unusually low stand of the sea that terminated the deposition of the Ochlockonee Formation in the Gulf Trough. During this low stand event, the flanks of the trough were probably subaerially exposed and the sea extended up the length of the Gulf Trough as a shallow, environmentally-restricted, long, narrow embayment. I envisage the dolomitization as being early diagenetic in origin, having occurred before the deposition of the overlying Okapilco Limestone.
Age
All known fossils in the Wolf Pit are very poorly preserved molds and casts in the dolostone and the age of the formation, therefore, cannot be paleontologically determined at this time. The age ofthe WolfPitDolostone can be extrapolated through the ages of the overlyingand underlying formations, and through physical correlation with Oligocene shelfdeposits outside ofthe GulfTrough. The overlying Okapilco Limestone contains a latest Vicksburgian, Bucatunna planktonic foraminiferal suite and is, therefore, correlated with the Bucatunna Clay of

42

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The areal distribution (subcrop) of the Wolf Pit Dolostone.

43

Mississippi and Alabama. The youngest Oligocene formations in Georgia
outside of the Gulf Trough are the Suwannee Limestone and, itslateral equivalentin the coastal area, the Lazaretto Creek Formation. The Suwannee Limestone is barren of planktonic foraminifera but the Lazaretto Creek Formation contains a small but consistent suite of planktonic foraminifera (see p. 82). These planktonic foraminifera indicate correlation of the Suwannee Limestone with the Byram Formation of Mississippi and not with the Bucatunna Clay of Mississippi and Alabama.
Based on biostratigraphy and stratigraphic position, the age of the Suwannee Limestone is consistent with correlationwith the ByramFormationwhich underlies the Bucatunna Clay. Therefore, interpretation suggests that the Wolf Pit Dolostone was deposited during a severe low stand of the sea after Byram and Ochlockonee deposition, and prior to Bucatunna and Okapilco deposition. The age of the Wolf Pit Dolostone would then be, Early Oligocene, lateVicksburgian (late Rupelian) in age. It is suggested here that the Wolf Pit low stand is related to the planktonic foraminiferal zone boundary between the Cassigerinella chipolensis-Pseudohastigerina micra Zone and the Globigerina ampliapertura Zone of Stainforth and others (1975)(Pl. 1).
OKAPILCO LIMESTONE, new name
Definition
The Okapilco Limestone is named here for a distinctive calcarenitic, colonial coral-bearing limestone formation at the top of the Oligocene section within and on the westernflank of theGulf Trough and interior of the Chattahoochee Embayment in Georgia. The Okapilco Limestone has been referred to the Suwannee Limestone (Zimmerman, 1977; Gelbaum and Howell, 1982) and the Byram Formation (Sever and Herrick, 1967) in the past.
Type Section
The nameOkapilcois takenfrom Okapilco Creek, approximately 1.75miles (2.8 km) eastofthe type locality. The type localityof the Okapilco Limestone is the core site oftheColquitt5(GG5-3199),approximately3.5miles(5.6 km) northwest of the court house at Moultrie, Colquitt County, Georgia (Fig. 11). The type section or unitstratotype (holostratotype) of the formation occurs in the interval396 feetto 535 feet in the core (Fig. 19). The upper boundary stratotype of the Okapilco Limestone occurs at 396feet where the Okapilco Limestone is overlaindisconforrnably by the Lower Miocene Parachucla Formation. The lowerboundary stratotype of the formation occursat 535 feet in the core where it overlies with apparent discornforrnity the Wolf Pit Dolostone. The site of the core

Coffee 4 (GG5-3541) is here designated a reference locality and the core is a parastratotype of the Okapilco Limestone. The core site of the Coffee4 (GG5-3541) is approximately 1.7 airline miles (2.7 km) northeast of the community of Pridgen in northern Coffee County, Georgia (Fig. 15). The reference section of the Okapilco Limestone is the interval568 feet to 675 feet. In this core, the Okapilco Limestone is overlain disconformably by the Parachucla Formation. It overlies with apparent disconforrnity the Wolf Pit Dolostone.
The site of the core Berrien 10 (GGS-3542) is also designated a reference locality and the core is a parastratotype of the Okapilco Limestone. Core recovery in the Okapilco section in the Berrien 10 is only 34%. However, typical coralline limestone is present in the core and the core is, therefore, designated a reference section. The core site of the Berrien 10 (GG5-3542) is approximately 2.1 airline miles (3.4 km) northeast of the village of Enigma in northwestern Berrien County, Georgia (Fig. 2).
The reference section of the Okapilco Limestone is the interval604 feet to 662 feet in the core. -The member is overlain disconformably by the Parachucla formation and occurs above a core gap of 59 feet. The Pridgen Limestone Member of the Ochlockonee Formation is present below the core gap at 721 feet and the Wolf Pit Dolostone presumably occurs in the core gap between 662 feet and 721 feet in the core.
Lithology
The Okapilco Limestone consists of sporadically dolomitized limestone that is massive and structureless, varyingly indurated and recrystallized, sporadically chalky, moderate to coarsely but irregularly granular in texture, finely bioclastic, variablymacrofossiliferous, and variably porousand dense. The three cores that penetrate this unit in the GulfTrough contain common to abundant colonial corals or coral heads, suggesting that this limestone is coral-rich and locally may be a coralline limestone. Other fossils include scattered molds of mollusks, seattered occurrencesoflargerforaminifera (Lepidocyclina spp. and Nummulites sp.), and rare bryozoa and miliolid foraminifera. Locally the Okapilco Limestone is pyritic, and rarely it has abundant pyrite in the upper part.
The Okapilco Limestone is characterized by its uneven or irregular bioclastic texture, by its variable porosity and chalkiness, by locally common occurrence of pyrite, and in its tendency to be fossiliferous, and especially by the common occurrence or abundance of colonial corals.
Stratigraphic Relationships
The Okapilco Limestone is restricted to the Gulf

44

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45

Trough and to the interior of the Chattahoochee Embayment. It occurs from the vicinity of Coffee County in the northeast to at least central Colquitt County in the southwest (Fig. 20) but its southwestern limit is not known (see discussion on p. 42). Vaughan (1900) described a coralline limestone that contained twenty-five to thirty species of coral near Bainbridge, Georgia. Therefore, correlation of the above coralline limestone would appear to be a possibility. There are also massive coral heads near the top ofthe Bridgeboro Limestone at Climax Cave in Decatur County near Bainbridge, and scattered coral heads in the Bridgeboro Limestone at the type locality. The scattered occurrence of massive corals, therefore, is characteristic ofthe Bridgeboro Limestone. It is not likely, however, that the coral reef described by Vaughan (1900) is Okapilco Limestone because the limestone he described occurs at a low elevation along the Flint River (probably now submerged under Lake Seminole). it is evident from Plate 3 that the Flint River flows northwest of the Gulf Trough and, in Decatur County, Georgia, probably flows along the northwestern flank of the trough. Because the top of the Bridgeboro Limestone exposed in Climax Cave is roughly 6 miles (9.5 km) troughward of Vaughan's coral locality and occurs at a considerably higher elevation, it would appear that the coral locality of Vaughan (1900) occurs stratigraphically low in the Bridgeboro Limestone. On the other hand, it is possible that the corals at the top of the Oligocene section at Climax Cave (Bridgeboro Limestone) may represent the western feather edge of the Okapilco Limestone because of the proximity of the cave to the northwestern flank of the Gulf Trough. If so, the Wolf Pit Dolostone occurs in a disconformity at Climax Cave. Finally, the Okapilco Limestone is not recognizable in well-cuttings from its stratigraphic position in the Cairo test well (GG5962) in Grady County, Georgia, and is not known to occur in the Chattahoochee Embayment in Gadsden County, Florida. The northeastern limit of the Okapilco Limestone is also unknown, but the undifferentiated calcareous sand and sandy limestone formation occurs in a similarstratigraphicpositionin theGulfTroughin Toombs County, Georgia.
The Okapilco Limestone overlies the Wolf Pit Dolostone with apparent disconformity from Colquitt County to the vicinity of Coffee County. The Parachucla Formationofthe Hawthorne Group disconformablyoverlies the Okapilco Limestone. The Okapilco Limestone is 210 feet (64 m) thick in the type core Colquitt 5 (GG53199), 138 feet (42 km) thick in the core Coffee 4 (GGS3541), and is at least 58 feet (18 m) thick in the core Berrien 10 (GG5-3542).
Due to the deposition of approximately 320 feet (98 m) of Lower Oligocene limestones, the Gulf Trough was considerably shallower by the time the Okapilco Limestone was deposited. The common occurrence of

coral-heads in the limestone suggests the sea floor of the trough was within.the photic zone but the paucityofother macrofossils suggestsan unsuitable environmentfor most larger benthic organisms.
Age
The Okapilco Limestone is correlated with the Bucatunna Oay of Mississippi and Alabama on the basis of planktonic foraminifera. The planktonic foraminifera identified from the Okapilco Limestone at the depth of 666 feet in the core Coffee 4 (GG5-3541) include the following:
Globigerina anguliofficinalis G. ouachitaensis G. eocaena Globorotalia opima nana Chiloguembelina cubensis
The absence of Globorotalia increbescens, Globigerina ampliapertura, and Pseudohastigerina spp. from this association is critical. These three planktonic foraminifera occur in the Byr~ Formation and lateral equivalents, and are consistently absent in the Bucatunna Clay, even in moderately rich assemblages. Therefore in this report the Okapilco Limestone is correlated with the Bucatunna Clay of Mississippi, Alabama and western Florida and is latest Vicksburgian in age. The consistent absence of Globorotalia increbescens and Pseudohastigerina spp. in the Bucatunna Clay and Okapilco Limestone suggests that these two formations occur above the Cassigerinella chipolensis-Pseudohastigerina micra Zone and probably, therefore, occur within the Globigerina ampliapertura Zone (Pl. 1).
BRIDGEBORO LIMESTONE, new name
Definition
The name Bridgeboro Limestone wasintroduced informally by Huddlestun (1981) and was adopted by Manker and Carter (1987, p. 187) in their paleoecological study of the formation. The Bridgeboro Limestone is formally named here for a rhodolithic limestone that occurs on the flanks of the Gulf Trough in the central and southwestern Ge6rgia Coastal Plain (Pl. 3). In the past, the Bridgeboro Limestone was included in part in the Flint River formation (Cooke, 1943, p. 81-83), Suwannee Limestone (Cooke, 1945; Owen, 1963, p. 19-21; Glawe, 1974, p. 16), and Vicksburg.Group (Applin and Applin, 1964, p. 211). The Duncan Church beds of western Florida (Cole, 1934; Vernon, 1942; Cooke, 1945; Purl and Vernon, 1964) also are included in the Bridgeboro Limestone in this report.

46

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The areal distribution (subcrop) of the Okapilco Limestone.

47

Type Section
The name Bridgeboro is taken from the community of Bridgeboro in southwestern Worth County, Geogia. The type locality of the Bridgeboro Limestone is the southern-most pit of the Bridgeboro Lime and Stone Company, south of Georgia highway 112 in Mitchell County, Georgia, 6.5 miles (10.4 km) west-southwest of the community of Bridgeboro (Fig. 21). The section of Bridgeboro Limestone exposed in the pit is the type section or unit-stratotype (holostratotype) of the formation (Fig. 22). The lower contact is not exposed at the type locality, and the upper contact is a pinnacled solution surface with overlying clay residuum (Bucatunna Clay?) containing silicified Oligocene fossils.
In Florida, the lime pit at Duncan Church is designated a reference section, parastratotype, and lower boundary stratotype of the Bridgeboro Limestone. The
lime pit at Duncan Church is located in NW1 I 4, SE. 1I 4,
Sec. 36, T4N, R14W in northeastern Washington County, Florida. Only the basal 10 feet (3 m) of the formation is exposed in the lime pit but the lower gradational and uneven contact with the Marianna Limestone is wellexposed. Similarly, the interval 8 feet to 40 feet in the Florida Geological Survey core Duncan Church 1 (W11487) taken at a site near the lime pit is designated a parastratotype of the Bridgeboro Limestone. The section in the upper part ofthe core is very similar to thatexposed in the pit. Finally, the Florida Geological Survey core Hunt 1 (W-10954) is designated a parastratotype of the Bridgeboro Limestone in Florida. This is the southernmost known occurrence of the formation. The site of the Hunt 1 (W-10954) is in the center of the NEl/4, Sec.16, T1N,R14Winsouth-centralWashingtonCounty,Florida. The parastratotype section occurs in the interval174 feet toT. D. at 226 feet. The Bridgeboro Limestone is overlain disconformably in this core by the basal Miocene Chattahoochee Formation at 174 feet, the younger Oligocen~ being absent at the site.
Lithology
The Bridgeboro Limestone is a rhodolithic limestone and it is the abundance of rhodoliths ("rounded nodules of clastic limestone" of Owen, 1963, p. 19) in a rnatrixofvariablybioclastic calcarenite that distinguishes this formation. The abundance of rhodoliths varies from bed to bed. In some beds the rhodoliths are packed close together and impart a rubbly appearance to the bed. In other beds the rhodoliths do not dominate the lithology so completely, and the limestone takes on a more massive, uniform appearance. However, whether the rhodoliths are common or rare in a specific bed, they are always present in typical Bridgeboro deposits. The observed size of the rhodoliths range from less than 0.5 inch

(1 em) to as much as 5 inches 13 em). Manker and Carter (1987, p. 182) described the rhodoliths and associated beds from the Bridgeboro Limestone at the type locality as follows:
The 21 meters of exposed limestone is dominated by a densely packed mass of algal rhodoliths.... Field measurements show approximately 294 rhodolithslm2 in general, the number of rhodoliths remains nearly constant throughout most of the section; however, some variations have been noted. Three (1-3 m) thick zones of matrix-rich, algal-poor beds ~40 rhodolithslm2) occur with.in the quarry section. One of these zones corresponds to the upper 2 meters of the section and was sampled for paleoecologic analyses. The number of rhodoliths also varies laterally within the limits given above.
Compared to the rhodoliths the encloing matrix is relatively soft, thereby facilitating the collection of algae for laboratory investigation. Throughout the exposed section, but most noticeably in the upper 15 meters, rhodoliths and enclosing carbonate sand matrix have in part been replaced by chert.
Although silicification occurred in discrete beds 0.5-1.0 m thick, these chert beds are not continuous throughout the quarry. Lenses and pockets of a yellowish-green clay intercalated with the algal limestone occurs most in the upper 15 meters of the section. X-ray diff~action (XRD) analysis shows the clay to be smectite, which swells to 17 (Angstroms) upon glycol solvation (Bowman and Manker; 1982)....
The matrix lithology qf the Bridgeboro Limestone typicallyconsistsofa fairly uniform, even-textured, granular calcarenite. The calcarenite particles generally consist of very fine- to medium-grained bioclastic debris most ofwhich is unidentifiable as to origin. Recognizable particles consist of fragments of bryozoa, foraminifera, echinoderms, rhodoliths, and rare calcitic mollusk fragments. Some scattered beds or lenses contain more coarsely bioclastic calcarenitic limeston_e in which the larger foraminifer Lepidocyclina is conspicuous. In some beds at the type locality of the Bridgeboro Limestone, the matrix lithology consists of a fine-grained calcarenite

48

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49

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50

which is lithologically similar to the Marianna Limestone.
Degree of consolidation of the calcarenite ranges from soft and unaltered to indurated. Most commonly, however, the matrix is only lightly to moderately recrystallized and is rather soft and easily eroded. Because of the typically soft nature of the calcarenite matrix and the hard, resistantrhodoliths, corerecoveryinthe Bridgeboro Limestone is characteristically poor. Commonly the only sediments recovered are small rhodoliths and rhodolith fragments.
Other than rhodoliths and bioclastic debris, the Bridgeboro Limestone is only moderately fossiliferous. Macrofossils that do occur consist of mollusk molds and casts, Chlamys anatipes, C. duncanensis scattered occurrences of the echinoid Clypeaster cotteaui, bryozoa, and rare molds of colonial coral heads. The colonial coral heads are more commonly found near the top of the formation, where they get rather large and abundant. Other than rhodoliths, the only fossil that has been identified to date and that is moderately common in the formation is Lepidocyclina. At the type locality, Lepidocyclina ranges in abundance from common to rare and is spotty in distribution. Some zones or small lenses contain abundant Lepidocyclina. This sporadic distribution of Lepidocyclina appears to be typical of the Bridgeboro Limestone in the subsurface of Colquitt, Thomas, and Brooks Counties on the southern flank of the Chattahoochee Embayment. Some beds or intervals in the cores from that area consist of coquinoid Lepidocyclina limestone, and is lithologically reminiscent of.the correlative Florala Limestone or the underlying Ocala Limestone. However, the Lepidocyclina in the Bridgeboro Limestonecanbe strikinglylarge, exceeding the diameter of the ~ore (1-7/8 inches):
The Bridgeboro is a relativelypurelimestone and there are few other subordinate lithic components of the formation. Irregularly occurring clasts and smeared out clasts of very fine grained sand and films of greenish waxy clay are present at the type locality but elsewhere, quartz sand and clay minerals are not apparent in the formation. Dolostoneoccurs atthe baseofthe Bridgeboro Limestone on the shelf south of the Chattahoochee Embayment but dolostone or dolomite are not known to be present elsewhere. On the other hand, clay and chert occurrence near the top of the formation is common but results largely from weathering and solution.
Stratigraphic Relationships
The Bridgeboro Limestone occurs in two disconnected bands, one along the northern flank of the Gulf Trough and the other along the southern flank of the Gulf Trough (Fig. 23). These two separate occurrences of the formation are divided by the Gulf Trough. On the north-

em flank of the trough, the Bridgeboro Limestone grades laterally and troughward into the deeper water Florala Limestone Member, and the Florala Limestone grades troughward into the relatively deep water Ochlockonee Formation within the channel. Presumably the same facies relationships applies to the southern flank of the trough as well.
The northern band of Bridgeboro Limestone (on the northern flank of the Gulf Trough) extends from the vicinity of Dublin in Laurens County, in the northeast, southwestward to at least Decatur County, a distance of approximately 100 miles (160 km). The Bridgeboro Limestonehasnot yetbeen traced southwestward into Jackson County, Florida. However, itis exposedinalimestone pit in northeastern Washington County, south of Chipley, Florida (formerly Duncan Church beds) and is present in the Florida Geological Survey core Hunt 1 (W-10954) in southern Washington County, Florida.
The northern band of Bridgeboro Limestone appears to be no more than 20 to 30 miles (32 to 48 km) across at the most and itgradeslaterally northwestward into the Marianna? and Glendon Limestones in the Ocmulgee River area. Farther southwest, in Worth and Dougherty Counties, the outcrop belt of the Bridgeboro Limestone occurs in the Dougherty Plain where its former presence is indicated by the occurrence of rhodolith-bearing chert rubble and boulders. Presumably, the Bridgeboro Limestone graded laterally northwestward into the Marianna Limestone and Glendon Limestone on the Dougherty Plain, but it possibly could have graded directly into the siliciclastic Shellstone Creek beds. The Oligocene occurs today only as a residuum over the Dougherty Plain (Fig. 10). In western Florida and in Mitchell and Colquitt Counties, Georgia, the stratigraphic relationships indicate that the Bridgeboro Limestone grades both laterally westward and embaymentward into the stiller water Florala Limestone Member by elimination of rhodoliths.
The southern belt of Bridgeboro Limestone (on the southern flank of the Gulf Trough) occurs in Thomas, Brooks and Colquitt Counties. There is also some evidence that it may occur in Cook County (see McFadden and others, 1986,p.233-234). Thesouthernbandisatleast 13 miles (21 km) long, and may be more than 25 miles (40 km) long. It is not known to be more than approximately 10miles (16 km) across. The southern band of Bridgeboro Limestonegradeslaterallysoutheastward into the Ellaville Limestone and Suwannacoochee Dolostone? in Thomas and Brooks Counties (Pl. 3). The regional stratigraphic relations!_lips indicate that the Bridgeboro Limestone is a carbonate facie~t is strongly influenced by the presence of the Suwannee Current.
There is no subsurface information on which to determine the formation underlying the Bridgeboro Limestone along the northern flank of the Gulf Trough. However, based on the stratigraphic cross-section between

51

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The areal distribution (outcrop and subcrop) of the Bridgeboro Limestone in Georgia.
52

Albany and Moultrie, Georgia (Pl. 3), it would appear that the Bridgeboro in its type area could be unusually thick and disconformably underlain by the Ocala Limestone, gradationally underlain by the Marianna Limestone (as at Duncan Church), or gradationally underlain by the Florala Limestone Member. In the type area of the formation, the upper contact relationships are ambiguous and the Bridgeboro Limestone occurs at the top of the local section or is overlain by residuum. At the type locality, the pinnacled top of the Bridgeboro Limestone appears to be overlain by residuum of the Bucatunna Clay, somewhat similar to that at the type locality of the Florala Limestone Member. At Climax Cave in Grady County, Georgia, the Bridgeboro occurs at the top of the Oligocene section and is disconformably overlain by the Lower Miocene Chattahoochee Formation (Huddlestun, 1988). At Rockhouse Cave near Cordele in Crisp County, on the other hand, the Bridgeboro Limestone is disconformably overlain by the Suwannee Limestone and a 6 inch (15 em) thick bed of dark chert that occurs in the stratigraphic position of theSuwannacoochee Dolostone separates the two formations.
The Bridgeboro Limestone crops out in scattered areas along the northern belt. The southern belt of the formation occurs only in the shallow subsurface. The southern Bridgeboro Limestone disconformably, or with apparent gradation due to dolomitization, overlies the Ocala Limestone. It is overlain by the Suwannee Limestone but the nature of the contact is obscure due to poor core recovery in the Bridgeboro.
The Bridgeboro Limestone is distinguished from the adjacent and superjacent limestone formations in containing common to abundant rhodoliths. Although rhodoliths also occur in the Ocala Limestone, Ellaville Limestone and SuwanneeLimestone, theyare never common in those formations. Typical Bridgeboro Limestone is distinguished from the Florala Limestone Member in containing abundant, rounded rhodoliths and common to abundant Lepidocyclina whereas the Florala Limestone contains consistently abundant Lepidocyclina and scattered occurrences of abundant encrusting or anastomosing algae.
The Bridgeboro Limestone is at least 65 feet (20 m) thick at the type locality. Although the pinnacled and weathered top of the formation is exposed there, the lower contact is not, and the complete thickness of the formation at the type locality is not known. In ten cores scattered through the southern belt of the formation in southeastern Colquitt, northeastern Thomas, and northwestern Brooks Counties (Fig. 2). the Bridgeboro Limestone ranges from 25.5 feet (7.7 m) to 92.5 feet (28m) thick, withanaveragethicknessofapproximately55feet(17m).
The Bridgeboro Limestone was deposited on the flanks of the Gulf Trough in moderately deep water but still within the photic zone, and under relatively high

energy conditions. The occurrence of the Bridgeboro Limestone in close proximity to the GulfTrough indicates that the Suwannee Current also influenced the depositional environment in its vicinity (also see Huddlestun and others, in review). Manker and Carter (1987, p. 185187) described the paleoecology of the Bridgeboro Limestone at the type locality as follows:
Both Archaeolithothamnium and Lithoporella are warm watergenera with the latter being more common on tropical reefs (Adey and Macintyre, 1973; Wray, 1977). Archaeolithothamnium prefers, but is not restricted to, lower light intensities, which imply a deeper water environment. Lithoporella, because ofits dominance on reefs, may indicate shallower water with greater light intensity, although no precise information for this genus has been found.
A consideration of the shape/sphericity and internal growth patterns of the rhodoliths gives some indication of depth. In a study of Recent rhodoliths, Bosellini and Ginsburg (1971) noted that those specimens that were spherical or compact displayed an internal laminar growth pattern. Those algae that were trapped in beds of turtle grass tended to be discoidal to flat and had a columnar growth pattern. The majority of the specimens collected during this study were compact and displayed a laminar growth pattern. This suggests that the rhodoliths grew under relatively high-energy conditions that moved them frequently, implying depths that are shallower than what might typically be expected for Archaeolithothamnium. The bladed to platy specimens observed in this investigation were found in association with pockets and lenses of swelling clays. They usually occurred at the bottom and in margins of the pockets, indicating that the algae had been trapped in a depression and rendered immobile. These depressions were subsequently filled with swelling clay.
Since Lit~oporella, which is a shallow water alga, tends to be more abundant at the top of the quarry section, a change in water depth with time may be inferred. A general shoaling, either due to

53

a sea-level change or the build-up of the algal facies probably occurred.
Because the biota can be characterized as a low-diversity community dominated by red algae..., it may have been subjected to a type of environmental stress that would have restricted or excluded a more diverse and abundant biota. However, the kinds of species that are present (including the red algae) suggest that such stress could not have resulted from abnormal salinity, sea -water chemistry, or turbidity. The paucity of fine-grained sediment supports a low-turbidity environment, and the nature of the faunal assemblage itself implies a warm, normal marine open-ocean setting. We suggest that the mechanism causing the low species diversity in this environment was the irregular and mobile substrate produced by the rhodoliths.
Most of the species... can be shown to have some specific adaptation for an irregular, mobile substrate. These adaptations include the ability to bore into or encrust upon the algae, and the ability to reside in interstices between rhodoliths. In addition, some species' mobility or large size relative to rhodoliths may have aided in their survival on the substrate. Lithophaga nuda survived in this environment by boring into the nodular algae. Its frequent occurrence in collections... along with the numerous borings observed in sectioned rhodoliths demonstrates its abundance.
Attachment or encrustation upon rhodoliths or other skeletal remains was another common survival strategy. The solitary coral Trochocyathus(?) attached to rhodoliths or dead tests of Clypeaster cotteaui and cheilostornes encrusted the tests of Lepidocyclina and rhodoliths. Sabellarid(?) worm tubes also encrusted the alga. Oysters displaying irregular attachment scars on their valves suggest that they also attached to'the rhodoliths.
Chlamys duncanensis and Chlamysanatipes

(seallops) probably relied upon their mobility and crevice-dwelling habit to cope with the shifting substratum, as do modern species of this genus (Kauffman, 1969; Stanley, 1970). Lima was probably byssally attached within crevices between rhodoliths. Modern species of Lima live interstitially in cobbly substrata (Kauffman, 1969; Stanley, 1970). Lepidocyclina may also have lived between the rhodoli!}ls.
Borers and encrusters were often found in life position within the rhodolith-rich facies... . This was not true, however, for other species that were large and mobile, such as Conus sp. and other snails, echinoids, and bivalves; these species were more frequently in life position in rhodolith-poor carbon.ate sands, where they were more abundant than in rhodolithdorninated environments... . Therefore, their presence in the rhodolith facies may reflect post-mortem transport from a sandy environment. For example, autecological analysis of Conus (Kohn, 1959), Rhyncholampas (Mortensen, 1948a; Kier, 1962, 1975; Gladfelter, 1978), Clypeaster (Mortensen, 1948b, Glycymeris, Pitar, and Phacoides (Kauffman, 1969; Stanley, 1970), suggests that these organisms have preferences for sandy substrata. Modern specjes of Brissus also inhabit mixed sand and gravel substrata (Kier, 1984; Kier and Grant, 1965).
Age
The age of the Bridgeboro Limestone is Early Oligocene, Vicksburgian (Rupelian). All of the principal macrofossils of the formation are known to occur only in Vicksburgian formations in the type provincial Vicksburgian in Mississippi and Alabama.
The following macrofossils are present in the Bridgeboro Limestone at the type locality:
Clypeaster cotteaui C. rogersi (?) Rhyncholampas gouldii Chlamys duncanensis C. anatipes
In Mississippi, Clypeaster cotteaui is khown to occur only in the Glendon Limestone (M. Hunter, pers. corn., 1986) and C. cotteaui occurs in the Florala Limestone Member in

54

Alabama. Clypeaster rogersi has been reported from the Marianna Limestone, Mint Spring Formation, Glendon Limestone, and ByramFormationinMississippi (MacNeil and Dockery, 1984, p. 19), and from the Marianna and Glendon Limestones in Alabama (Cooke, 1926). Rhyncholampas gouldii is reported from the Mint Spring Formation (Cooke, 1959; MacNeil and Dockery, 1984, p. 19) and Marianna Limestone (MacNeil and Dockery, 1984, p. 19) inMississippi, but has not been reported from Alabama. Chlamys anatipes has been reported from the Forest Hill Formation, Mint Spring Formation, Marianna Limestone and Glendon Limestonein Mississippi (Glawe, 1974; Dockery, 1982), and from the Red Bluff Clay, Marianna Limestone, Glendon Limestone and Byram Formation in Alabama (Cooke, 1926; Glawe, 1974; Dockery, 1982). It isalso found in the Bumpnose Limestone in Florida (MacNeil, 1944c, p. 1324; Moore, 1955, p. 38, 41; Glawe, 1974) and the Marianna Limestone in Georgia (Glawe, 1974). Chlamys duncanensis has been reported from the GlendonLimestone and ByramFormation in Mississippi and Alabama (Glawe, 1974; Dockery, 1982), from the Bridgeboro Limestone at Duncan Church (Mansfield, 1934; Glawe, 1974), Bucatunna-equivalent limestone at Natural Bridge in Walton County, Florida (Glawe, 1974), and from the Marianna Limestone in Georgia (Glawe, 1974). Because neither the lower Vicksburgian Red Bluff Clay nor the Bumpnose Limestone contain Clypeaster rogersi but, rather, an undescribed species of Clypeaster, and because the Bridgeboro Limestone is overlain by the Vicksburgian Suwannee Limestone on the southern flank of the Chattahoochee Embayment, it appears that the Bridgeboro Limestone is correlative with only the middle part of the Vicksburgian section of Mississippi and Alabama (i.e., to the Glendon and possiblyMarianna Limestones). However,atDuncan Church the Bridgeboro Limestone gradationally overlies the Marianna Limestone. Finally, Bryan and Huddlestun (1990) produced evidence that the Bridgeboro'Limestone at its type locality (which is the upper part of the formation) is correlative only with the Glendon Limestone of Mississippi and Alabama.
Based on the above discussion, the Bridgeboro Limestone occurs within the Cassigerinella chipolensisPseudohastigerina micra Zone of Stainforth and others (1975), and within Zones P18-P19 of Blow (1969)(Pl. 1).
FLORALA LIMESTONE MEMBER OF THE BRIDGEBORO LIMESTONE, new name
Definition
The FloralaLimestone was informallyintroduced by Bryan (1991) and is formally proposed here for a fossiliferous, Lepidocyclina-rich, nonrhodolothic, and sporadically algal-rich, subdivision of the Bridgeboro Lime-

stone. In the type area, the Florala Limestone Member occurs seaward of the Vicksburg Group. Relative to the Vicksburg Group, the Florala Limestone appears to represent a farther offshore, possibly deeper, and a more still-water (but still within the photic zone) facies. When compared to typical Bridgeboro Limestone, the Florala Limestone again seems to represent an environment in which the water was probably deeper and more still than is indicated for the Bridgeboro. Because Florala lithology has been observed only on the northern flank of the Gulf Trough in Georgia, troughward of the typical Bridgeboro Limestone, it appears that in Georgia the Florala Limestone may have been deposited in deeper water than the Bridgeboro, below the main influence of the Suwannee Current but still within the photic zone. The lithology of the undivided Bridgeboro Limestone, then, appears to have been deposited under the direct influence of the Suwannee Current whereas the Florala Limestone Memberand the formations of the Vicksburg Group were little effected or influenced by it.
The Florala Limestone Member in the central panhandle of Florida has been generally referred to the Suwannee Limestone (Cooke, 1945; Purl and Vernon (1964); SChmidt, 1984). MacNeil (1944c), however, correlated the Florala Member at its type locality with the Duncan Church beds of Washington County, Florida, which in this report are included in the undivided Bridgeboro Limestone.
Type Section
The name Florala is taken from the town of Florala, near the Alabama-Florida state line in southern Covington County, Alabama. The type locality of the Florala Limestone is here designated the lime pit of the Stovall Lime and Cattle Co., Inc. The Stovall lime pit is located approximately 7 miles (11 kril) east of Florala, Alabama, on Alabama state highway 54 in Covington County. The pit is located in the SE1/4, Sec. 22, TlN, R20W, in the Hacoda, Alabama, 1:24,000quadrangle map (Fig. 24). The section of Florala Limestone Member exposed at the type locality is the unit-stratotype (holostratotype) of. the formation (Fig. 25).
The type section also contains the upper boundary stratotype of the member. The Bucatunna Clay disconformably overlies the Florala Limestone Member near the top of a hard ledge, approximately 50 feet (15 m) above the floor of the pit.
The following Florida Geological Survey cores are designated reference sections and parastratotypes of the Florala Limestone Member of the Bridgeboro Limestone: The core Mathis 1 (W-8102), taken approximately 6 miles (10 km) west-southwest of the type locality in NE, NW1/4, NW1/4, SW1/4, Sec. 36, T6N, T21W, Walton County, Florida is a refernce section and parastratotype.

55 .

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1 KILOMETER
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Figure24.

The type locality of the Florala Limestone Member of the Bridgeboro Limestone (U. S. Geological Survey, Hacoda, Ala. 1:24,000 topographic quadrangle.
56

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LIMESTONE VICKSBURGIAN
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The parastratotype section of the Florala Limestone occurs in the interval274 feet to total depth at 375 feet. The core Brown 1 (W-8104), was takenapproximately4 miles (6krn)southofthe localityinNW1/4, NW1/4, NW1/ 4, Sec. 11, T5N, R20W, Walton County, Florida (Fig. 5). The parastratotype sectionofthe Florala Limestone in the Brown 1 occurs in the interval 203 feet to 272 feet. The above cores are stored at the Florida Geological Survey in Tallahassee, Florida.
Lithology
The lithology of the Florala limestone Member of the Bridgeboro Limestone in its type area consists of relatively pure, coarsely fossiliferous, Lepidocyclina-rich, variably algal-rich limestone. However, farther south in the subsurface of Walton County, Florida, the Florala Limestone also contains lenses of sucrosic, tan to brown dolostone invaryingstagesofdolomitization thatappear to be laterally continuous only over short distances. Encrusting algae areconspicuous and ubiquitous at the type localitybutnot in the reference cores. These algae appear to be related to the rhodoliths of the typical Bridgeboro Limestone but they are encrusting and flat, not spheroidal like the Bridgeboro rhodoliths, nor anastomosing as some algae in limestone in the Gulf Trough in Florida. Other than dolomite and dolostone, no other mineral components of the lithology have been observed.
The Florala Limestone Member is vaguely and rudely stratified, but the stratification may not be apparent except through the concentration of encrusting algae or the predominantly horizontal layering of the Lepidocyclina and other flat fossils. At the type locality, the limestone appears to be generally massive and structureless except for some thin intervals of up to 2 feet (0.6 m) thick of more coarsely fossiliferous, rubbly limestone. The rest of the limestone contains much micrite and chalky matrix calcite. The lower several feet exposed at the type locality contains more common encrusting algae than the overlying sections, producing distinct, thin- to medium-bedded stratification in the limestone. Where the encrustingalgae is less concentrated, the stratification ismuch thickerand tends to bemassive and structureless. In these intervals, flat or discoidal fossils vary from random in orientation to a moderate, horizontal orientation.
The limestone is generally partially consolidated but friable and soft, and there are intervals or lenses within the limestone that are also hard and recrystallized or completely unconsolidated and uncemented. The abundance of the encrusting algae probably contributes to the cementing of the calcitic and biogenic debris.
Althoughthe FloralaLimestoneMemberisrichly fossiliferous, the faunal diversity is low, typical of all of the Oligocene lirnestonesofthe southeastern United States.

The predominantbiotic elements ofthe limestone include Lepidocyclina spp., encrusting alg~e, local concentrations of Nummulites panamensis, some bryozoa, and rare echinoids, scattered pectinids, molds of mollusks, and corals. The Lepidocyclina are variably sellaeform but some flat variants are also present. In some cores, the Lepidocyclina are principally flat.
The Florala Limestone Member is distinguished lithologically from typical Bridgeboro Limestone by the absence of rhodoliths and either the absence or scattered occurrences of abundant encrusting algae as opposed to rhodoliths of the undifferentiated Bridgeboro. Where encrusting algae are absent in the Florala Limestone Member, the formation canbeidentified asaLepidocyclinarich limestone of the Ocala type, though of lower faunal diversity. In addition, Nummulites is locally common to abundant or absent in the Florala Limestone but is not known to occur in the Bridgeboro Limestone
Stratigraphic Relationships
It is postulated here that the Florala Limestone Member represents deposition under far-offshore, relatively deep and still-water, photic zone conditions. The sediments are part of the carbonate continental shelf facies of the Vicksburgian of southern Alabama and western Florida, west of and on the northern flank of the Gulf Trough (Chattahoochee Embayment)(Fig. 26). In the vicinity of the Chattahoochee Embayment (Georgia Geologic Survey core Colquitt 11 GGS-3545), the Florala facies appears to occur along the northwestern flank of the embayment at intermediate depths as a relatively narrowbandofsubsurfacedeposits gradingdownsection and troughward into the Ochlockonee Formation.
The FloralaLimestoneMemberis predominantly a subsurface formation but it is known to crop out in southeastern Covington County, Alabama. The Florala Limestone is known to underlie the central Florida panhandle, at least as far west as Walton County, Florida. It occurs as far east as the northern flank of the Gulf Trough within the upper part of the Oligocene sequence in the western part of the Chattahoochee Embayment as far north as Colquitt County, Georgia. However, the subsurface data in the western part of the Chattahoochee Embayment southwest of Colquitt County is sparse. The Florala Limestone member is not known to occur in Jackson County, Florida, where its stratigraphic position northwestofthe embaymentis occupiedby the Vicksburg Group. The correlative stratigraphic interval within the northern flank of the embayment may occur in a very narrow band in the subsurface, between the Marianna/ Glendon Limestones and the Ochlockonee Formation. The lithologyofthe Florala Limestone cannotbe discriminated in the well-cutting descriptions of Moore (1955). Westofthe Chattahoochee EmbaymentinWaltonCounty,

58

Figure26.

The areal distribution (subcrop) of the Florala Limestone Member of the Bridgeboro Limestone in Georgia.

59

Florida, the Florala Limestone Member occurs at least as far south as the coastal area of Florida.
In its typearea inthevicinityofFlorala, Alabama, the Florala Limestone Member appears to consist of the offshore, lateral, stratigraphic equivalents of the Marianna?, Glendon Limestones and possibly the Byam Formation; Itisdisconformablyoverlainby theBucatunna Clay in its type area but farther south irrthe subsurface of western Florida, the Florala Limestone appears also to include the stratigraphic equivalent of the Bucatunna Clay. The discontinuities representing the low sea level stands between the various Vicksburg Group formations are not evident within the Florala Limestone except, possibly, as discontinuous beds or lenses of dolostone'Qr dolomitized limestone within the Florala Limestone. The Florala Limestone Member appears to grade laterally eastwardinthevicinityoftheChattahoocheeEmbayment into typical Bridgeboro Limestone. At Duncan Church the Bridgeboro Limestone gradationally overlies the Marianna Limestone.
The lithofacies interpretation of the Vicksburg Group, Bridgeboro Limestone, and Florala Limestone Member of the Bridgeboro adopted in this report is that the Florala Limestone is an offshore, deeper water but still relatively shallow water (within the photic zone) correlative of the Vicksburg Group and relatively still-water facies of the Bridgeboro Limestone. The Florala Limestone Member appears to grade laterally into typical Bridgeboro Limestone near the western margin of the Chattahoochee Embayment and in the vicinity of the Suwannee Current.
Along the western flank of the Chattahoochee Embayment (Gulf Trough), the Florala also appears to occur in a deeper water, trough-ward position to the Bridgeboro Limestone and, therefore, reflects a deeper water origin. The type locality of the Bridgeboro Limestone occurs in northeastern Mitchell County, Georgia, northwest of the Gulf Trough (Chattahoochee Embayment)(Fig. 2). The core Colquitt 11 (GG5-3545), taken near Doerun in northwestern Colquitt County between the Gulf Trough and Bridgeboro type locality, encountered only Florala Limestone Member that gradationally overlies the Ochlockonee Formation (Pl. 2). Typical Bridgeboro Limestone is absent in the Colquitt 11 (GG5-3545). Onthe western margin of the Chattahoochee Embayment, then, deposition of the Florala Limestone represents a later period of channel filling when the embayment floor had been raised through carbonate sedimentation into the photic zone.
The Florala Limestone Memberofthe Bridgeboro Limestone disconformably overlies the Ocala Limestone in the northern panhandle of Florida west of the Chattahoochee Embayment. In its type area, the Florala Limestone Member is disconformably overlain by the Bucatunna Clay. In all known occurrences of the Florala

Limestone in the subsurface west of the Choctawhatchee River in the panhandle of Florida, the member is overlain disconformably by Bucatunna-equivalent limestone (as at Natural Bridge in northern Walton County, Florida) or Chickasawhay?-equivalent limestone. East of the Choctawhatchee River, the Florala Limestone Member is disconforrnably overlain by the Chattahoochee Formation. In the Colquitt 11 (GG5-3545) in northwestern Colquitt County, the Florala Limestone is gradationally
overlain py the late Vicksburgian Suwannee Limestone
(Pl. 3).
Age
The age of the Florala Limestone Member of the Bridgeboro Limestone is Early Oligocene, Vicksburgian. The Florala Limestone is a lithofacies of the Bridgeboro Limestone and is, therefore, considered to be the same age as the Bridgeboro (Pl. 1). Stratigraphic position supports this correlation. Along the southern flank of the Gulf Trough, the Bridgeboro Limestone is overlain by the Suwannee Limestone, considered here to be correlative with the Byram Formation. At Duncan Church in Washington County, Florida, the Bridgeboro Limestone conformably overlies the Marianna Limestone. In addition, Bryan and Huddlestun (1990) demonstrated a biostratigraphic correlation that is most compatible with the Glendon Limestone, thereby supporting physical correlation with the Glendon Limestone. However, the Bucatunna Oaydisconforrnablyoverlies the FloralaLimestone in its type area, and this leaves open the possibility that the Byram stratigraphic interval has not been satisfactorily distinguished paleontologically from the Glendon stratigraphic interval in an open shelf, fossiliferous limestone facies. Similarly,Plate3 suggests that there may be a thick section of Oligocene limestone below the floors of the limestone pits near Bridgeboro in Mitchell County. This raises the possibility that a lower partof the Bridgeboro Limestone may also be a lithofacies of the Marianna Limestone.
There appear to be no lithologic discontinuities or breaks within the few completely cored Florala Limestone sections in western Florida. There is likewise no stratigraphicevidence thatthe Bumpnose Limestone may grade laterally seaward into the Florala.
Vicksburgian macrofossils identified at the type locality in the Florala Lime~tone include the following:
Chlamys anatipes Pycnodonta vicksburgensis Clypeaster cotteaui C. rogersi Brissus bridgeboroensis Macropneustes mortoni Lytechinus floridanus

60

the larger foraminifera include:
Lepidocyclina (Eulepidina) undosa L. (Nephrolepidina) yurnaguensis Nummulites panamensis
(Heller and Bryan, 1991)
The Florala Limestone contains the following planktonic foraminifera (at 290 feet, 294 feet, 305 feet, 317 feet, amd 374 feet) from the core Mathis 1 (W-8102) in Walton County, Florida:
Globorotalia increbescens Globigerina ampliapertura G. eocaena G. ouachitaensis Pseudohastigerina barbadoensis Chiloguembelina cubensis
The association of planktonic foraminifera is compatible
with the Cassigerinella chipolensis-Pseudohastigerina micra
Zone. In view of the above discussion, the best age
approximation that has been determined for the Florala Limestone is Glendon- to possibly Byram-equivalency.
FLORIDA BANK STRATIGRAPHIC ASSOCIATION
ELLAVILLE LIMESTONE, new name
Definition
The name Ellaville Limestone is proposed here for a subsurface limestone of southwestern Georgia that crops out along the Suwannee and lower Withlacoochee
at Rivers in Madison, Hamilton, and Suwannee Counties,
Florida. In this area, and especially Ellaville on the Suwannee River, the type locality of the formation (Fig. 27), the Ellaville Limestone has been assigned to various formations in the past. At the type locality, Matson and Clapp (1909) referred the limestone to the Hawthorne Formation whereas Cooke and Mossom (1929, p. 72-73, beds 1and 2) referred itto the Glendon Limestone. Cooke and Mansfield (1936) discussed all the carbonates exposed along the Suwannee River between Ellaville and White Springs. They proposed the name Suwannee Limestone for the yellowish upper beds (beds 3 and 4 of Cooke and Mossom, 1929) and they called the lower limestone at Ellaville (beds 1 and 2 of Cooke and Mossom, 1929) "white limestone containingVicksburg(Oligocene) fossils" (Ellaville Limestone of this report). They considered the Suwannee Limestone to disconformably overlie the "white limestone containing Vicksburg (Oligocene) fossils" ..

Cooke (1945) included the "white limestone" of Cooke and Mossom (1929) in the "ByramLimestone" and the overlying carbonates (including the Suwannacoochee Dolostone of this report) in the Suwannee Limestone.
MacNeil (1944c) identified Turritella martinensis in this
limestone at Ellaville and, as a result ofhis investigations, he correlated the limestone with the lowest Oligocene Forest Hill Sand and Red Bluff Clay of Mississippi. Purl and Vernon(1964, p.110) included beds 1 and2ofCooke and Mossom (1929) in the Suwannee Limestone, and Hunter (1972) followed MacNeil (1944c) and informally included the "white limestone" in the Bumpnose Lime-
stone on the basis of the occurrence of T. martinensis.
Type Section
The name Ellaville is taken from the community of Ellaville on the Suwannee River in Hamilton County, Florida. The type locality of the Ellaville Limestone is here designated the exposures ofthe limestone atEllaville on the left bank of the Suwannee River in Suwannee County, Florida (Fig. 27). The section of the Ellaville Limestone exposed at the type locality is the unitstratotype (holostratotype) of the formation (Fig. 28). The Ellaville Limestone of this report is the same as beds 1 and 2 at Ellaville of Cooke and Mossom (1929) and Purl and Vernon (1964). The type locality of the formation is near the center of Sec. 24 in TlS, RUE, and the formation crops out discontinuously along the Suwannee River from the vicinity of Dowling Park, approximately 10 miles (16 km) south (downriver) frornEllaville, to 1 mile (1.6 km) northeast (upriver) from Ellaville. The type locality contains the upperboundary stratotype of the Ellaville Limestone. The Suwannacoochee Dolostone gradationally and conformably overlies the Ellaville Limestone approximately 8 feet (2.4 m) above mean low water of the Suwannee River. The lower boundary stratotype is not exposed at the type locality. In any event, the lower boundary is difficult to distinguish in outcrop along the river due to case hardening of the limestones and I have not beenable to identify a satisfactory lower boundary stratotype in outcrop (Fig. 28).
The Florida Geological Survey core Ellaville 1 (W-10657) taken at the type locality is here designated a reference section and parastratotype of theEllavilleLimestone (Figs. 27 and 28), which occurs in the interval25 feet
to 39 feet in the core. The core site is at Ellaville in SW 1I
4, NE1/4, Sec. 24, TlS, RllE. The lower boundary stratotype of the formation isat39 feet in the core and the
Ellaville Limestone overlies the Ratularia vernoni Zone of
the "Ocala Limestone" abruptly and with apparent discontinuity. The Ellaville 1 (W-10657) is stored at the Florida Geological Survey in Tallahassee, Florida.
In Georgia, the core Thomas 4 (GGS-3188) [U.S. Gypsum core 76-1]) is herein designated a reference

61

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Figure27.

The type localities of the Ellaville Limestone and Suwannacoochee Dolostone, and the reference locality of the Suwannee Limestone (U.S. Geological Survey, Ellaville, Florida, 1:24,000 topographic quadrangle).

62

ELLAVILLE 1 (W-10657)
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Composite stratigraphic section along the Suwannee River from Dowling Park to the confluence with the Alapaha River compared with the Florida Geological Survey core Ellaville 1 (VV-10657).

63

section and parastratotype of the Ellaville Limestone.. tain thickness of dolostone occurs in the lower part of the

The core site of the Thomas 1 (GGS-3188) is on the side of Ellaville.

an abandoned railroad grade, less than 0.1 mile (0.16 km)

The Ellaville Limestone typically is massive and

south of the crossing of Old Quitman Road and the structurelessbut thereissome rude and vagueorganization

railroad crossing, approximately 2.4 airline miles (3.8 ofthesedimentsintolayers. Stratificationismostnoticeable

km) northeast of the center of the village of Boston in where there are varying abundances of macrofossils in

Thomas County, Georgia (Fig. 2). The Ellaville Lime- different beds or strata in the section. The Ellaville is

stone occurs in the interval273.5 feet to 311.5 feet in the indurated and recrystallized to varying degrees. Uncon-

core. The core Thomas 4 (GGS-3188) is stored at the solidated limestone is not known to occur in the forma-

Georgia Geologic Survey in Atlanta, Georgia.

tion.

Lithology

Stratigraphic Relationships

The Ellaville Limestone is a lithologically nondistinctive, sparsely but variably macrofossiliferous, calcarenitic, relatively pure, moderately indurated limestone. Dolomite and dolostone are the only significant minor lithic components of the formation and they occur rarely and sporadically. There are no known occurrences of clay, quartz sand, glauconite, phosphate, orgypsum in the formation.
The calcarenitic particles consist of bioclastic debris and range in size from medium sand-size to siltsize with some minor coarse, porous, well-washed, foraminiferal-pelletal arenite. The more finely granular limestone is also more chalky ormicritic. Little of the granular calcarenitic material is identifiable as to origin: most is probably algal but foraminifera, especially miliolids, can be recognized with a hand lens even where the limestone appears well-cemented. The roundness of the particles ranges from well-rounded to angular and the coarser bioclastic particles are generally the more angular.
Macrofossils occur in stratified concentrations. They largely consist of mollusk molds and casts of small to moderate size. The most abundant mollusks are small species of Turritella that include T. mississippiensis and T. cf. martinensis (fide Dockery). In places, rhodoliths and corals are conspicuous, but they are never as abundant as in the correlative Bridgeboro Limestone. Lepidocyclina is generally present in any given sectionbut is not common in the type area. In Georgia, however, the lower part of the Ellaville Limestone locally consists of a coarsely fossiliferous, Lepidocyclina-rich limestone that resembles the correlative Florala Limestone to the west of the Gulf Trough and the Rotularia vernoni. Zone of the Ocala Limestone in Florida. Bryozoa are generally associated with Lepidocyclina, but the bryozoa appear always to be a subordinate element of the fauna and lithology. Lepidocyclina commonly is distributed in vague layers, the intervening intervals generally consisting of calcarenitic limestone.
Sucrosic, tan to brown, hard and dense to soft and porous dolostone occurs locally within the Ellaville Limestone. In Georgia, dolomitization has occurred near the Ellaville-Ocala boundary and a variable and uncer-

The Ellaville Limestone is known to occur in Thomas and Brooks Counties, Georgia, and in Madison, Hamilton, and Suwannee Counties, Florida (Fig. 28). It also probably underlies Lowndes County, Georgia, and Jefferson County, Florida. It thins and pinches out eastward in Georgia and Florida in the vicinity of the Peninsular Arch, and grades laterally northwestward into the Bridgeboro Limestone (Pis. 3 and 4). The southern limit of the formation is not known at this time.
The Ellaville Limestone overlies the Ocala Limestone with apparent disconformity. InGeorgia, extensive dolomitization has occurred near the Ellaville-Ocala boundary and the contact relationships, therefore, are uncertain. I have been unable to distinguish a clear formational contact in outcrop along the Suwannee River in Florida but, in t.he parastratotype core Ellaville 1 (W10657), the contact is distinct at 39 feet in the core and appears to be an abrupt change in limestone beds. The Ellaville Limestone is overlain conformably and gradationally in the type area and in Georgia by the Suwannacoochee Dolostone.
Farther down river from Ellaville, below the I-10
highway bridge on the left bank of the river in SE1 I 4,
SW1/4, Sec. 35, T1S, R11E, fossiliferous limestone containing the echinoid Wythella eldgridei and a worm case, Rotularia vernoni (= Spirulaea vernoni) occurs at approximately 18 feet (5.5 m) below the top of the Ellaville Limestone (Fig. 27). Lithologically this limestone is not Ellaville Limestone and more closely rt;?sembles the Ocala Limestone. In the Ellaville 1 (W-10657), the top of the Upper Eocene Ocala Limestone occurs at a paraconformable lithologychange at59 feet, below which Aequipecten spillmani, Amusium ocalanum, typical Nummulites wilcoxi, and Asterocyclina are present. Hunter (1976 and pers. com., 1991) considers the Rotularia vernoni Zone of Purl (1957) to be earliest Oligocene in age and correlative with the Red Bluff Clay and Bumpnose Limestone of the easter:n Gulf Coastal Plain. The lithology of the limestone containing R. vernoni on the Suwannee River is compatible with the lithology of the limestone that contains the Oligocene echinoid Clypeaster cotteaui at the Steinhatchee pit in Dixie County, Florida, formerly

64

N
t

0 10 20 30 40 50

E3

H

miles

~' VOLUSIA
l, '-./"", r\J

Figure29.

The areal distribution (outcrop and subcrop) of the Ellaville Limestone in Georgia and northern Florida.
65

included in the Ocala Limestone. Clypeaster cotteaui is

known to occur only in the Glendon Limestone in Missis-

. sippi but it also occurs in the Florala Limestone in

Albama and in the Bridgeboro Limestone in Georgia

(considered to be Glendon-equivalent at the Bridgeboro

type locality). I could find no fossils in the limestone

containing R. vernoni on the Suwannee River that are

clearly restricted to sediments of Eocene age such as

Amusiumocalanum,Aequipectenspillmaniand discocyclinid

larger foraminifera. Therefore it is possible that what has

been called the top oftheOcalaLimestoneontheSuwannee

River may be an unnamed Oligocene limestone that is

lithologically similar to the Ocala Limestone as is the

Bumpnose Limestone. This particular limestone re-

sembles the Bumpnose Limestone and other richly fossil-

iferous Oligocene limestones in the low species diversity

of the fauna, but it is not Bumpnose Limestone in that it

is not glauconitic, a characteristic of all occurrences of

Bumpnose Limestone known to me. With the available

paleontological evidence, this Ocala-like Oligocene lime-

stone in northwestern Florida may range in age from

earliest Vicksburgian through middle (Glendon-equiva-

lent) Vicksburgian. Such a correlation would suggest

that the Ellaville Limestone may grade southward into

Ocala-like limestone. Put the other way, Ocala-like Oli-

gocene limestone in peninsular Florida may grade north-

ward into the Ellaville Limestone with a slight

intertonguing relationship. This Ocala-like Oligocene

limestone is not known to occur in Georgia.



The Ellaville Limestone lithologically is a nonde-

script and nondistinctive limestone. It is typically mas-

sive with only thick and rude stratification, and is vari-

ably macrofossiliferous although most beds are only

poorly fossiliferous. In contrast, both the underlying

Rotularia vernoni Zone and "Upper Eocene" Ocala Lime-

stone are abundantly macrofossiliferous. The Ocala !ilso

contains a rich and diverse suite of macrofossils and

larger foraminifer whereas most of the Ellaville typically

contains relatively few larger foraminifera. The overly-

ing Suwannacoochee Dolostone, on the other hand, is a

gray to tan, poorly fossiliferous to nonfossiliferous, fine-

grained, sucrosic dolostone. In contrast, the Suwannee

Limestone has a granular, "mealy'' texture that is rarely

seen in the Ellaville. The Suwannee Limestone rarely

contains larger foraminifera and is generally

nonmacrofossiliferous but contains local concentrations

of macrofossil molds and casts. The laterally correlative

Bridgeboro Limestone is distinguished from the Ellaville

Limestone in containing abundant rhodoliths and more

common larger foraminifera.

Only about 8 feet (2:5 m) of the Ellaville Lime-

stone is exposed during mean low water at the type

locality on the Suwannee River. In the nearby reference

core, Ellaville 1 (W-10657), the Ellaville Limestone is 14

feet (4.3 m) thick (Fig. 27). In the Florida Geological

Survey core Bass 1 (W-10480) taken near the GeorgiaFlorida stateline near theWithlacoocheeRiverinHamilton County, Florida, approximately 20 miles (32 km) north of Ellaville, the formation is 12 feet (3.6 m) thick (Pl. 3).
In Georgia, the Ellaville Limestone is 36.5 (11.1 m) thick in the reference core Thomas 4 (GG5-3188) near Boston in Thomas County; 18.5 feet (5.6 m) thick in the Brooks7(GG5-3189)inBrooksCountynearPavo; and22 feet (6.7 m) thick in the core Brooks 8 (GG5-3208) in northern Brooks County (Fig. 2, 3). The Ellaville Limestone is at least 13 feet (4.0 m) thick in the core Brooks 9 (GG5-3209), but the lower part of the formation has been dolomitized in that core and the true thickness of the formation is uncertain.
Itwouldappearfromlimiteddata that the Ellaville Limestone averages between 10 feet (3.4 m) and 15 feet (4.6 m) thick in the type area. It thickens northwestward into Georgia to an average of approximately 25 feet (7.6 m) before it grades laterally northwestward into Bridgeboro Limestone.
The Ellaville Limestone was deposited in relatively shallow-water on the continental shelf in a banktype environment. The absence of cross bedding and the poorly bedded nature of the limestone indicates low energy conditions, probably below wave base. The climate was subtropical to tropical, probably much like that' of the Bahamas Islands of today.
Age
The age of the Ellaville limestone is Early Oliger cene, Vicksburgian (Pl.1). Macrofossils present in the Ellaville Limestone include:
Clypeaster rogersi (?) Rhyncholampas gouldii Turritella mississippiensis
In the type area of the Vicksburgian and Chickasawhayan in Mississippi and Alabama, all of the principal macrofossilsofthe Ellavillelimestoneareknown to occur only in' Vicksburgian formations. Clypeaster rogersi has been reported from the Marianna Limestone, Mint Spring Formation, Glendon Limestone, and Byram Formation in Mississippi (MacNeil and Dockery, 1984, p. 19), and from the Marianna and Glendon Limestones in Alabama (Cooke, 1926). Rhyncholampas gouldii has been reported from the Mint Spring Formation and Marianna Limestone in Mississippi (MacNeil and Dockery, 1984, p. 19), but has not been reported from Alabama. Turritella mississippiensis has been recorded only from the Byram Formation in Mississippi (MacNeil and Doc.kery, 1984, p. 50).
The earliest Vicksburgian Red Bluff Clay in Mississippi and Alabama, and the correlative Bumpnose

66

Limestone in Alabama and Florida do not contain Clypeaster rogersi but, rather, a smaller, undescribed and probably ancestral species. Therefore it is concluded that the typical Ellaville Limestone is younger than earliest Vicksburgian.
BecauseofthepervasiveindurationoftheEllaville Limestone, I have been unable to concentrate foraminifera from the formation. One can only identify a few smaller foraminifera, mainly miliolids, along fracture surfaces of the limestone. Lepidocyclina mantelli (= L. supera) is the only larger foraminifer that has been reported to date from the Ellaville Limestone (Cooke, 1945, p. 86) and it is known to range throughout the Oligocene of southeastern North America.
The Suwannee Limestone that overlies the Suwannacoochee Dolostone, which in tum overlies the Ellaville Limestone, is correlated with the Byram Formation of Mississippi. It is, therefore, concluded that the most likely age of the Ellaville Limestone is middle Vicksburgian, probably correlative with the Glendon Limestone (Pl. 1) as earlier proposed by Cooke and Mossom (1929).
SUWANNACOOCHEEDOLOSTONE, new name
Definition
The name Suwannacoochee Dolostone is proposed here for a lithologically distinctive and mappable dolostone formation in the area of the Suwannee and lower Withlacoochee Rivers in Madison, Hamilton, and Suwannee Counties, Florida, and in the subsurface of Thomas and Brooks Counties, Georgia. At Ellaville, Florida, the type locality of the formation (Fig. 26), the Suwannacoochee Dolostone has been included in the HawthomeFormation(MatsonandClapp,1909), Tampa Limestone (Dall, 1892; Cooke and Mossom, 1929), and SuwanneeLimestone (beds3 and 4 ofCooke and Mossom, 1929)(CookeandMansfield,1936;Mansfield,1937;Cooke, 1945; Puri and Vernon, 1964).
Cooke (1945, p. 98) did not recognize this unit as a dolostone (or dolomite) but his description of the Suwannacoochee at Ellaville is clear enough:
Most of the rock is cream-colored or yellow hard, compact limestone without apparent bedding planes; the lower 4 feet is thin-bedded and somewhat conglomeratic.
Although this dolostone consistently has been included in the Suwannee Limestone in recent years, I am excluding it from that formation because the Suwannacoochee is a mappable and lithologically distinctive stratigraphic unit. In addition, the Suwannacoochee Dolostone does

not appear to be a subdivision of the Suwannee Limestone but is more closely related to the pre-Suwannee Oligocene formations in the area. That is, the Suwannacoocheehasapproximatelythe samegeographic distribution as the underlying Ellaville Limestone, and it appears to grade' laterally into the upper part of the Bridgeboro Limestone in the same area where the Ellaville Limestone grades laterally into the lower part of the Bridgeboro (Pl. 3). The Suwannee Limestone overlies both the Suwannacoochee Dolostone and the Bridgeboro Limestone, and the thickness of the Suwannee is generally consistent over the entire area, suggesting that the Suwannacoochee is not a dolomitized lower phase of the Suwannee Limestone (Pis. 3 and 4).
Type Section
The name Suwannacoocheeistaken from a spring near the right bank of the Suwannee River opposite Ellaville,Florida. ThetypelocalityoftheSuwannacoochee Dolostone is designated here as the. exposures of the formation at Ellaville on the left bank of the Suwannee River in Suwannee County, Florida (Fig. 26). This is also the type locality of the Ellaville Limestone. The section of Suwannacoochee Dolostone exposed at the type locality is the unit-stratotype (holostratotype) of the formation (Fig. 27). The type locality of the formation is near the centerofSec.24inT1S,R11E,and the formation crops out discontinuously along the Suwannee River from the vicinity of Dowling Park approximately 10 miles (16 km) south of Ellaville, to 1.5 miles (2.4 km) northeast (upriver) from Ellaville. It also crops out discontinuously for approximately 4 miles (6.4 km) along the Withlacoochee River above its confluence with the Suwannee River. The best exposures of the Suwannacoochee Dolostone occur in low bluffs on the rig~t bank of the Suwannee River approximately 4 miles (6.4 km) south (downriver) from Ellaville inS 1/4, Sec.34, T1S,R11E. The lower boundary stratotype is present at the type locality where the Suwannacoochee Dolostone conformablyand gradationally overlies the Ellaville Limestone.
In Georgia, the core Thomas 4 (GGS-3188, U.S. Gypsum 76-1) is here designated a reference section and parastratotype of the Suwannacoochee Dolostone (Fig. 2). The site of the Thomas 4 (GGS-3188) is on the side of an abandoned railroad grade, less than 0.1 mile (0.16 km) south of the crossing of Old Quitman Road and the railroad right-of-way, approximately 2.4 airline miles (3.8 km) northeast of the center of the village of Boston in Thomas County-. Georgia. The Suwannacoochee Dolostone occurs in the interval217.5 feet to 273.5 feet in the core. This section has been chosen as a parastratotype because the lithology is typical for the formation, all the lithologic characteristics of the formation are present in this section, and the core recovery of more than 80% is

67

exceptionally good.
Lithology The Suwannacoochee Dolostone typically is a
gray or buff to tan to brown, thin-bedded to massive and structureless, fine-grained dolostone. Where post-depositional dolomitizationhas been extensive, the formation consists of buff to brown, sucrosic dolostone and, except for the basal part, is massive and devoid of sedimentary and biogenicstructures. However, where extensiverecrystallization has not obliterated the original sedimentary fabric of the formation, the dolostone is characteristically gray, very fine grained, slightly argillaceous, thinly bedded to laminated, and with scattered layers containing intraformational breccia (intraclasts). A thin marker bed of dark gray to black, dolomitic clay or buff, clayey dolostone consistently occurs at the base of the SuwannacoocheeDolostoneinThomasand Brooks Counties, Georgia. This clay bed, however, is not present at the type locality or in the type area along the Suwannee and lower Withlacoochee Rivers in Florida. In its place there is a thinly bedded dolostone with scattered layers of intraformational breccia (bed 3 at Ellaville of Cooke and Mossom, 1929; Cooke, 1945; Purl and Vernon, 1964). Also, in the type area, the Suwannacoochee is not known to contain the gray, thinly layered dolostone that is characteristic of the formation in Georgia. Recrystallization has been more extensive in the type area than in Georgia.
Subordinate lithic components of the Suwannacoochee Dolostoneinclude clay,rareoccurrences ofchert, and carbonaceous material in the lower part. The Suwannacoochee is an exceptionally hard and resistant dolostone and, as a result, where the formation occurs at river level, it forms a rubble of boulders and, in places, huge blocks of dolostone that form rapids in the rivers during low water stages.
The Suwannacoochee Dolostone is not typically fossiliferous. However, layers or bedding planes containing molds of very small mollusks (apparently a depauperate fauna), and thick intervals with rare, seattered, small mollusk molds and impressions are not uncommon. Cooke and Mossom (1929) reported echinoid molds (Rhyncholampas gouldii) in the upper, massive dolostone (bed 4) at the type locality.
Stratigraphic Relationships
The Suwannacoochee Dolostone is known to occur in Thomas and Brooks Counties, Georgia, and in Madison, Hamilton, and Suwannee Counties, Florida (Fig. 29) and is present in all wells and cores from this area. It also probably underlies Lowndes County, Georgia, and Jefferson County, Florida. In addition, there is some evidence that it occurs in Cook County, Georgia, and partsofTaylorCounty,Florida. TheSuwannacoochee

Dolostone either pinches out or wedges out eastward in Georgia and Floridain the vicinityofthe PeninsularArch, and it appears to grade laterally northwestward into the upper part of the Bridgeboro Limestone (Pis. 3 and 4). The southern extent of the formation is unknown at this time.
The Suwannacoochee Dolostone overlies the Ellaville Limestone conformably and with apparent gradation. It is overlain conformably and with apparent gradation by the Suwannee Limestone. The Suwannacoochee Dolostone is distinguished from all other formations in the area in being a dolostone with thin bedding and with scattered beds containing intraformational breccia.
In the type area along the Suwannee River, the thickness of the Suwannacoochee Dolostone ranges from 11 feet (3.4 m) to 15 feet (4.5 m). It is 15 feet (4.5 m) thick at the type locality and is 16.5 feet (5.0 m) thick in the Florida Geological Survey core Bass 1 (W-10480) in Madison County near the Withlacoochee River. In Thomas and Brooks Counties, Georgia, the Suwannacoochee Dolostone ranges in thickness from 9.5 feet (2.9 m) in the core Brooks 8 (GGS-3208) to 56 feet (17m) in the reference core Thomas 4 (GGS-3188).
The scattered occurrence of unusually small mollusks, the presence of thin bedding and lamination, the presence of intraclast beds, and the presence of carbonaceous clay are all suggestive of a low-energy, biologically restricted, possibly intertidal or supratidal environment. The above characteristics, in addition to the decline in fossil content upward through the section from the Ocala Limestone through the Ellaville Limestone to the Suwarinacoochee Dolostone, is suggestive of a progressive shoaling. Therefore it appears that the SuwannacoocheeDolostonewas deposited ina relatively shallow water, low-energy environment (with periodic higher energy that resulted in the ripping up of bottom sediments). Being a shallow water shelf carbonate, the Suwannacoochee Dolostone, as with all shallow water shelf carbonates, was deposited in a tropical-subtropical climate.
Age
The age of the Suwannacoochee Dolostone is early Oligocene, Vicksburgian (Rupelian) (Pl.l). The Suwannacoochee is overlain and underlain, and grades laterally into Vicksburgian formations. Occurrence of Rhyncholampas gouldii in the Suwannacoochee is consistent with a Vicksburgian age. The Suwannacoochee Dolostone is gradationally overlain by the Suwannee Limestone that, on the basis of physical and biostratigraphic correlation, is correlated with the Byram Formation of Mississippi. The Suwannacoochee is abruptly but gradationally underlain by the Ellaville Limestone that is

68

N
t
~ 32
Atlantic ,. Ocean

0 10 20 30 40 50

E3

H

miles

Figure30.

The areal distribution (outcrop and subcrop) of the Suwannacoochee Dolostone in Georgia and northern Florida.
69

roughly correlated with the Glendon Limestone. Therefore it would appear that the Suwannacoochee Dolostone was deposited during the low stand of the sea subsequent to the deposition of the Glendon but prior to the deposition of the Byram in Mississippi (Pl. 1).
SUWANNEE LIMESTONE, redefined and revised

typically exposed along the Suwannee River in Florida, from Ellaville, where it unconformably overlies white limestone containing Vicksburg (Oligocene) fossils, almost to White Springs, near which it lies unconformably below the Miocene Hawthorn formation, ...

Definition
The Suwannee Limestone is recognized and described here as a lithologically distinctive stratigraphic unit that occurs in Georgia from the Florida state line to the Savannah River. Like the earlier Upper Eocene Ocala Limestone, the SuwanneeLimestone occurs onbothsides of the Gulf Trough in Georgia and occurs east of the eastern termination of the trough. However, its occurrence north of the Gulf Trough is much more restricted than its occurrence south of the trough. The Suwannee lithostratigraphic unit was not deposited west of the vicinity of the Chattahoochee Embayment (contrary to past stratigraphic usage west of the Apalachicola River). In that area, either the Bridgeboro Limestone or the Florala Limestone Member of the Bridgeboro occurs in the Suwannee stratigraphic position or the Suwannee stratigraphic-equivalent is not present in western Florida (due either to nondeposition or removal prior to the deposition of the Bucatunna Clay and correlative limestones).
The name Suwannee Limestone was proposed by Cooke and Mansfield (1936, p. 71-72) for "...yellowish limestone typically exposed along the Suwannee River in Florida, from Ellaville,...., almost to White Springs,...." .2 In Florida this section along the Suwannee River had previously been referred to vaguely as the Hawthorne Formation (Matson and Clapp, 1909) and Tampa Limestone (Cooke and Mossom,1929, p. 89-91). In Georgia, the Suwannee Limestone of this report had been included in the Jacksonboro limestone (Dall and Harris, 1892, p. 8384), the Chattahoochee Formation (Veatch and Stephenson,1911,p.339,341; Brantly,1916, p. 25-28),and both the Flint River formation (p. 83-84) and Suwannee Limestone (p. 84-86) by Cooke (1943). On the other hand, in Georgia, both the Bridgeboro Limestone (Owen, 1963; Glawe, 1974) and the Ochlockonee Formation (Gelbaum and Howell, 1982) have been included in the Suwannee Limestone.
Thelithostratigraphicdefinitionofthe Suwannee Limestone has never been clear. This results from (1} the original ambiguous lithostratigraphic definition of the formation by Cooke and Mansfield (1936, p. 71)
The name "Suwannee Limestone" is proposed for yellowish limestone

(2) from confusion resulting from the absence of the Suwannee Limestone (in the lithostratigraphic sense of this report) from the most commonly cited reference locality at Ellaville on the Suwannee River (compare with Cooke, 1945, p. 85-86; Purl and Vernon, 1964, p. 10); (3) from extension of the formation name, on the basis of stratigraphic position, to other Oligocene limestone lithostratigraphic units (Vernon, 1942, p. 59)3;
As used in this report the Suwannee limestone includes all limestone beds lying below definite Tampa formation and above definite Marianna limestone.
and (4}, from identification of the "Suwannee Limestone" based on Oligocene fossils (Vernon, 1951, p. 175).
As used in this report the Suwannee limestone includes all beds of Oligocene .age in Citrus and Levy Counties.
Based on a survey of the literature, it is concluded that the Suwannee Limestone of previous usage has largely been a biostratigraphic "formation" that required identification of Oligocene or "Suwannee" fossils for formation recognition(compare with Mansfield, 1937, 1938; Cooke, 1945; Vernon, 1942, 1951; MacNeil, 1944c, 1946). Rarely has the Suwannee Limestone been treated primarilyasalithostratigraphicunit(comparewithCooke,
2Cooke and Mansfield (1936) first described the formation, but their publication was in an abstractandcontained little information. The first adequate description of the Suwannee Limestone in the type area appeared in Cooke (1945, p. 86-104). Within the period 1936-1945, however, the name Suwannee Limestone was adopted by many workers.
3However, "the light gray limestone underlying Holmes and Washington Counties that bears the Marianna fauna described by Cushman (1922a, 1923), and Cole and Ponton (1930) is mapped as Marianna in the report" (Vemon,1942, p. 51) and, "As used in this report the term Tampa formation applies to all sediments lying above the Suwannee limestone and below the Alum Bluff group." (Vemon, 1942, p. 68).

70

1943, p. 84-864;Puriand Vernon, 1964, p. 105-114, Fig. 13; macrofossiliferous and bioclastic in some scattered strati-

Hendry and Sproul, 1966, p. 58-60; Yon and Hendry, graphic intervals o.r lenses.

1972; Randazzo, 1972). Most commonly, based on my

interpretation of the various texts, it appears that the Type Section

Suwannee Limestone has been recognized more on the

combination of fossil content and stratigraphic position

The Suwannee Limestone was named for the

than on any single criterion. The extent to which earlier Suwannee River in northern Florida. No specific type

authors based their recognition of the Suwannee Lime- locality or type section was ever designated for the

stone on lithologic characteristics other than limestone is Suwannee Limestone. Rather, Cooke and Mansfield

problematical because, in most texts, little weight had (1936, p. 71-72) only described a type area:

been given to discussion ofthe lithologyof the formation.

The concept of the Suwannee Limestone of the

..yellowish limestone typically exposed

present report is lithostratigraphic. Definition of the

along the Suwannee River in Florida,

Suwannee lithostratigraphic unit is based on the lithol-

from Ellaville, ...almost to White Springs, ...

ogy and stratigraphic relationships of the limestone crop-

ping out along the Suwannee River as defined by Cooke Later, Cooke (1943, p. 84) commented that:

and Mansfield (1936) and Cooke (1945). Based on my

field knowledge of the limestones iri the type area of the

The type area is along the Suwannee River

Suwannee Limestone, there is only one limestone forma-

above the bridge of the Seaboard Railway

tion that crops out along the Suwannee River from ap-

at Ellaville, Fla.

proximately 1.5airline miles (2.4 km) northeast of Ellaville

to the vicinity of White Springs. This limestone However, Cooke (1945, p. 86) reverted to the original

lithostratigraphic unit must serve as the central concept concept of the type Suwannee Limestone:

of the Suwannee Limestone of Cooke and Mansfield

(1936) and Cooke (1945). Furthermore, the lithology of

The name 'Suwannee limestone' was

this limestone formation isbroadlycompatible with much

proposed by Cooke and Mansfield

of the limestone in northern Florida that has been called

(1936, p. 71) for yellowish limestone

Suwannee Limestone on the basis of stratigraphic posi-

typically exposed along Suwannee

tion and fossil content (Mansfield, 1937; MacNeil, 1944c,

River in Florida from Ellaville almost

1946; Cooke, 1945; Vernon, 1951; Purl and Vernon, 1964)

to White Springs.

and more recentlyonlithology (Hendry and Sproul, 1966;

Yon, 1966,YonandHendry, 1972;Randazzo, 1972). There-

From this, it is concluded that Cooke and

fore, the lithostratigraphic conceptofthe Suwannee Lime- Mansfield (1936) and Cooke (1943, 1945) did not intend to

stone of this report is compatible with both the lithology designate a specific type locality for the Suwannee Lime-

of the Suwannee Limestone section cropping out along stone, but only a type area. And, there has never been a

the Suwannee River in the type area of the formation, and formally designated type locality or type section for the

with field identifications of the formation in northern formation.

Florida by most previous workers. In the type area of the

The section exposed in the bluffs along the

Suwannee Limestone, and in most of northern Florida Suwannee River at Ellaville has been the most generally

-.~-~ Georgia, the Suwannee Limestone can be described citedreferencelocalityoftheSuwanneeLimestone(Cooke,

as a very pale orange (10 YR 8/2), massive-bedded and 1945, p. 85-86; Puri and Vernon, 1964, p. 110; also see

structureless to rudely and thickly stratified, fine- to Cooke and Mossom, 1929, p. 72-73). Cooke (1945) in-

coarse-grained, even-textured and mealy- textured cluded the lower partof this section, "beds 1and 2", in the

(granular), variably soft and hard limestone that gen- "Byram limestone" (Ellaville Limestone of this report)

erally contains no macrofossils but which is richly and the upper part of the section, "beds 3 and 4", in the

Suwannee Limestone (Suwannacoochee Dolostone of this

report). Purl and Vernon (1964), on the other hand,

included the entire carbonate section exposed at J;:llaville

in the Suwannee Limestone.

It is my contention, however, that no Suwannee 4Although Cooke's concept of the Suwannee Limestone was generally Limestone, in the strict sense of the name and the sense

that of a biostratigraphic "formation", his treatment of the Suwannee adhered to in this report, is exposed in the bluff at Ellaville.

Limestone in the Geology of the Coastal Plain of Georgia closely The Suwannacoochee Dolostone, ''beds 3and 4" ofCooke

approximatesthelithostratigraphic conceptoftheSuwanneeLimestone (1945), represents a distinct, mappable dolostone unit

of this report.

(see p. 67-70 of this report) that lithostratigraphically is

71

not included in the Suwannee Limestone and has not been shown to be a lithofacies of the Suwannee Limestone. The Suwannacoochee Dolostone does appear, however, to grade laterally into the upper part of the Bridgeboro Limestone in Thomas and Brooks Counties, Georgia (Pis. 3 and 4). Similarly, the Ellaville Limestone that is exposed in the lower part of the bluff at Ellaville, beds 1 and 2 of Cooke (1945), has always been considered to be lithostratigraphically distinct from the Suwannee (except by Purl and Vernon, 1964).
The Suwannee Limestone is exposed less than 0.25 mile (0.4 km) downriver from the US 90 highway bridge at Ellaville and discontinuously for several miles farther downriver from Ellaville. This discontinuous occurrence results from structural undulation of the bed rock which alternately brings the top of the Ocala Limestone above river level and the Ellaville Limestone, Suwannacoochee Dolostone, and Suwannee Limestone down to riverlevel. Upriverfrom Ellaville, the Suwannee Limestone again dips down to river level at approximately 1.5 airline miles (2.4 km) northeast of Ellaville, and from there to the vicinity of White Springs the Suwannee Limestone is the only formation that crops out in place along the river.
To clarify the lithostratigraphy and the formation concept of theSuwannee Limestone, it is the intentof this writer to formally propose a principal reference locality and lectostratotype of the formation. Lithologically, the most typical Suwannee Limestone exposed in the type area of Cooke and Mansfield (1936) and Cooke (1943, 1945) occurs along a short reach of the river in or adjacent to Suwannee River State Park in Hamilton and and Suwannee Counties, Florida; from approximately
1.5 airline miles (2.4 km) northeast of Ellaville in NE1 I 4,
NW1/4, Sec. 18, TIS, R12E, upriver to S1/2, Sec. 5 and N1/2,Sec.8, T1S,R12E. Thebestsingleoutcropalongthis reach of the river occurs in a sharp bend of the Suwannee River in SW1/4, SE1/4, Sec. 7, TIS, R12E where approximately 16 feet (4.9 km) oflithologically typical Suwannee Limestone is exposed. The low bluff at this bend in the riveris proposedhereas theprincipal reference localityof the Suwannee Limestone (Fig. 26) and the section exposed at the principal reference locality is here designated the lectostratotype of the formation (Fig. 30). Although it is possible to reach the lectostratotype over land, access is difficult and the nearest road is more than 0.5 mile (0.8 km) from the exposure. The lectostratotype is easily accessible by small boat, however, and there is.an excellent boat ramp in Suwannee River State Park, 1.5 airline miles (2.4 km) downriver from the principal reference locality. As amended, the lectostratotype of the Suwannee limestone includes verypaleorange (10 YR8/ 2), massive-bedded and structureless to rudely and vaguely stratified and thick-bedded, mealy textured, soft to weakly indurated and friable, sparsely

macrofossiliferous limestone that overlies the Suwannacoochee Dolostone.
The Florida Geological Survey core Bass 1 (W10480) is here designated a reference locality and hypostratotypeof the SuwanneeLimestone. The core site of the Bass 1 (W-10480) is approximately 17 airline miles (27km) northwestofthe principalreferencelocalityofthe Suwannee Limestone, and is located less than 0.2 mile (0.32 km) south of.the Georgia-Florida state line near the center of Sec. 206, t3N, RlOE in Madison County, Florida (Fig. 2). The core site is approximately 0.5 mile (0.8 km) south of the Ga. 31 bridge crossing of the Withlacoochee River near the Georgia-Florida state line. The Suwannee Limestone occur~ in the reference core from approximately 23 feet to 175 feet and is approximately 152.5 feet (46.5 m) thick. However, 16 feet (4.9 km) of Suwannee Limestone is exposed alongthe Withlacoochee Rivernear the core site, indicating that the top of the Suwannee Limestone is at least as high as 90 feet above sea level in the vicinity of the core site. The elevation of the top of the Suwannee Limestone in the core Bass 1 (W-10480) is approximately 60 feet above sea level, indicating local topographic relief of at least 30 feet (9 m) on top of the formation. TheSuwanneeLimestone, therefore,isatleast 182.5 feet (55.6 m) thick in the vicinity of the core Bass 1 (W-10480). The Bass 1 (W-10480) is stored at the Florida Geological Survey in Tallahassee, Florida.
Lithology
Typical Suwannee Limestone consists of very pale orange (10 YR 8/2}, even-textured, and mealy (medium- to coarse-grained) limestone. The grains generally consist of roughly equidimensional, rounded, nondescript calcareous pellets that may be largely algal or fecal in origin (also see Randazzo, 1972), miliolid foraminifera, and fine, nondescript bioclastic debris. The grain-size of the pellets is variable, ranging from fine with much intragranular calcite "paste," to generally coarse and relatively wellsorted, with little calcite "paste." The Suwannee Limestone is soft to indurated and recrystallized, massivebedded and structurelessto rudelyJmtdistinctlybedded, and sparingly macrofossiliferous. Dolostone lenses or beds are generally rare in the Suwannee Limestone in Georgia except near its western limit (see Sever, 1966a, 1966b; Hendry and Sproul, 1966; Yon, 1966)in the vicinity of the Gulf Trough. In that area, dolomitization of the SuwanneeLimestoneappears to beextensive. Otherthan dolomite, subordinatelithic componentsofthe Suwannee Limestone are minor and the carbonate is fairly pure (probably greater than 95%). Quartz sand or silt is not apparent in the formation and conspicuous interstitial clay is rare in the formation. On the other hand, clay is more conspicuous,but still minor, in the upper part ofthe Suwannee Limestone in the Brooksville, Florida area,

72

(/

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z

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Figure31.

The measured lectostratotype of the Suwannee Limestone.

73

bothinterstitially and inirregular-shapedinclusions(also Stratigraphic Relationships

see Randazzo, 1972). Similarly, small lenses of chert

occurrarely throughout the Suwannee Limestone but the

The Suwannee Limestone underlies most of the

occurrence of chert is commonplace only in the upper Coastal Plain of southeastern Georgia from the Florida

part of the formation where there are lenses of massive state line in the south to the Savannah River in the

chert (silicified limestone) and chert concretions. In cores, northeast, and from the vicinity of the Pelham Escarment

small crystals of optically continuous selenite (gypsum) in Crisp County, Georgia, eastward to Screven County,

can be seen in places interstitial to the calcitic grains and Georgia (Fig. 31). The Suwannee Limestone is absent in

pellets. Glauconite and phosphate are unknown in the the Gulf Trough, in the coastal area of Georgia south of

Suwannee Limestone.

the vicinity of Glynn County, and it is likewise absent

Th,e granular quality of the Suwannee Limestone farther to the south in eastern Florida. Its distribution

is more pronounced than in the underlying Bridgeboro pattern in Georgia appears to be a broad, northeast-

Limestone, Suwannacoochee Dolostone, Ellaville Lime- southwest band parallel to the Gulf Trough.

stone, or Ocala Limestone in Georgia; or in the overlying

Typical Suwannee Limestone overlies the

Chattahoochee Formation. The Okapilco Limestone in Bridgeboro Limestone immediately east of the Gulf

the Gulf Trough is also characteristically granular in Trough in southwestern Georgia and north of the Gulf

texture but it is also commonly well-washed with much Trough in the central Georgia Coastal Plain. However,

lessintragranularcalcite. ThegranularityoftheSuwannee the Suwannee Limestone or its stratigraphic equivalent is

Limestone commonly remains evident where the lime- absent at the Bridgeboro type locality where residuum of

stone has been entirely converted to chert, leaving only Bucatunna Clay (?) disconformably overlies the

"ghosts" of the pellets and foraminifera within the trans- Bridgeboro Limestone. In most of Thomas and Brooks

lucent chert, or where the limestone has been completely Counties, Georgia, the Suwannee overlies the

recrystallized by calcite and is lacking in porosity. Suwannacoochee _Dolostone with apparent conformity.

Stratification in the Suwannee Limestone ranges Elsewhere in Georgia, the Suwannee Limestone

from massive and devoid of sedimentary and biogenic discoformably overlies the Ocala Limestone.

structures, to vaguely stratified, to prominently strati-

The Parachucla Formation of the Hawthorne

fied. Small-scale cross-bedding is present locally but is Group generally overlies the Suwannee Limestone dis-

rare and never prominent. In all of the cores that contain conformably in Georgia. Only in a small area east of the

Suwannee Limestone that I have examined, the forma- Chattahoochee Embayment in southwestern Georgia,

tion appears to be devoid of sedimentary structures other however, does the Chattahoochee Formation discon-

than gradual alternation in grain-size and alternation in formably overlie the Suwannee Limestone

induration or consolidation. In outcrop along the (Huddlestun, 1988). In its updip-most occurrences in

Suwannee River in Florida and along the Withlacoochee Crisp and Screven Counties, Georgia, theSuwanneeLime-

River in Florida and Georgia, the Suwannee Limestone stone is disconformably overlain by the Lower Miocene

generally is prominently stratified, with stratification Altamaha Formation.

commonly being irregular, rude, and characteristically

The Suwannee Limestone is distinguished from

defined by alternation between hard and soft limestone the underlying carbonates in consisting of very pale

(ledges and reentrants). Casual examination with a hand orange, granular, mealy textured, generally

lens, however, indicates that the characteristic granular nonmacrofossiliferous limestone. The Bridgeboro Lime-

lithology of the Suwannee Limestone prevails through- stone characteristically contains abundant rhodoliths

out the sections, from hard bed to soft bed, suggesting and scattered concentrations of Lepidocyclina (larger

that the prominent stratification seen in outcrop is a foraminfera). The Suwannacoochee Dolostone is

surficial phenomenon, perhaps related to ground-water charaterized as being a nonfossiliferous, either tan to

geochemistry in the limestone exposures.

brown sucrosic dolostone or light-gray, thinly bedded to

The Suwannee Limestone characteristically con- laminated dolostone. The Ocala Limestone is character-

tains few macrofossils, and large sections (e.g., along the ized as being richly bioclastic with abundant and varied

Suwannee River) may be entirely devoid of macrofossils larger foraminifera, and other varied biogenic debris

or visible bioclastic debris. In other places the Suwannee consistingofbryozoa, rhodoliths, echinoids, corals, molds

may be moderately macrofossiliferous with scattered of a varied suite of mollusks, and other nondescript

concentrations of Rhyncholampas gouldii or rich concen- biogenic debris in a variably indurated, chalky matrix.

trations of molluscan molds (typically with low diver- The overlying Parachucla Formation is variably sandy,

sity). Although Lepidocyclina occurs in scattered beds in argillaceous, dolomitic, calcareous, phosphatic, and

low or moderate abundance, I know of no abundant macrofossiliferous. The Chattahoochee Formation cosists

occurrences of larger foraminifera in the Suwannee Lime- predominantly of finely sandy dolostone with varying

stone in cores or outcrops.

amounts of clay or dolomitic clay beds.

74

N
t

J -32
'
Atlantic Ocean

Gulf of

0 10 20 30 40 50
E3 E'3 H

miles

Figure32.

The areal distribution (outcrop and subcrop) of the Suwannee Limestone in Georgia and northern Florida.

75

In the northern coastal area of Georgia, the Suwannee Limestone grades laterally eastward into the Lazaretto Creek Formation, a variably sandy, calcarenitic limestone to calcareous sand/sandstone. Except on the flanks of the Gulf Trough, where it is thought that the Suwannee grades laterally into the upper part of the Ochlockonee Formation, the Suwannee Limestone is not known to grade laterally into any other formation in the region.
The Suwannee Limestone averages about 100 feet (30 m) thick over most of the central Coastal Plain of Georgia butappears to systematicallythinnorthwestward and southeastward away from the Gulf Trough (Pl. 3). In the eastern part of the Coastal Plain in Georgia, it averages 50 feet (15 m) thick. Among 10 cores taken in Thomas, Brooks, and Colquitt Counties, Georgia (GG53213, GG5-3214, GG5-3215, GG5-3207, GG5-3211, GG53212, GGS-3208, GG5-3188, GG5-3189), the thickness of the Suwannee Limestone ranges between 104 feet and 152.5+ feet (32 and 46+ m), and averages approximately 120 feet (35m) . In the subsurface of the Savannah River area, the Suwannee Limestone ranges from 0 (locally), to approximately 50 feet (15m) thick and averages approximately 40 feet (13 m) thick.
The Suwannee Limestone was deposited on the Florida Bank and on the continental shelf in eastern Georgia in an environment free of siliciclastic sediments. In general, it appears that the water depth in which the Suwannee Limestone was deposited was relatively shallow. The scattered presence of small-scale cross-bedding suggests periods of relatively high wave or current energy on the bank and shelf. The abundance of what appears to be small, rounded pellets (which contribute to the mealy texture of the Suwannee) and the scattered occurrence of selenite gypsum within the formation also argues for a shallow-water environment (in the photic zone if the pellets are of algal origin), probably no deeper than 50 feet (15 m) and probably considerably less.
The paleontological evidence is compatible with a shallow-waterenvironmentfor the Suwannee Limstone with some evidence for the physical and chemical watermass conditions deviating from the stable, normal marine environment. The local abundance of the arenceous, carbonate banks foraminifera Dictyoconus, Discorinopsis, and Valvulina, three genera which do not occur with "normal" marine benthic faunas; the general abundanceofmiliolid foraminifera;thecompleteabsenceof planktonic foraminifera; the low diversity and high faunal dominance of the Mollusca in macrofossiliferous beds; and the scattered occurrences, and local abudance, of one species of echinoid, Rhyncholampas gouldii all suggest somewhat restricted marine conditions.
Age Originally, Mansfield (1937) and Cooke (1943,

1945) paleontologically correlated the Suwannee Limestone with the Chickasawhay Formation of Mississippi and Alabama. According to Mansfield (1937, p. 50):
A comparison of the fauna of the Suwannee Limestone with that of the Flint River formation (upper part of the Vicksburg), and other faunas similar to that of the Flint River formation, indicates that the fauna of the Suwannee Limestone as a whole lived during the latter part of the time represented by the Flint River formation and continued. on up to the end of the Vicksburg epoch.s
and (1937, p. 62):
Cooke correlates the Flint River formation (S.C., Ga., and Ala.) with the Chickasawhay marl member of Byram marl (Ala. and Miss.); ... The Flint River formation is correlated with the European Rupelian.
It is concluded in this report, however, that the age of the Suwannee Limestone is Early Oligocene, Vicksburgian (Rupelian)(Pl. 1). The principal macrofossils of the formation are known to occur only in the Vicksburg Group in the Vicksburgian type area in Mississippi and also in Alabama. None are presently known to
5Atthat time, the Chickasawhay was considered to be a member of the Byram which was a formation of the Vicksburg Croup. Therefore, the Chickasawhay was Vicksburgian in age by definition. The Flint River formation was believed to contain only a Chickasawhay fauna and, therefore, the Flint River was correlative with both the Chickasawhay FormationandVicksburgCroup. SubsequentlyMurray (1%1)formally split the Chickasawhay Formation from the Vicksburg Croup and assigned it spearate formation status and separate stage status (Chickasawhayan Stage). However, the surficial residuum of Georgia is now known to consist ofresiduum offossiliferous chert with silicified fossils ofnumerous ages,from Late Eocene to Miocene~ There are as yet no known fossils from the residuum and chert that contain specifically Chickasawhayanfossils.

76

occur in the Chickasawhay Formation. Because the upper part of the Oligocene lime-
stone sectionofpeninsularFlorida (post-SuwanneeLimestone of Yon and Hendry, 1972) has always been referred to as Suwannee Limestone and contains a distinctive molluscan fauna, it has always been correlated with the Chickasawhay Formation (Mansfield, 1937). The lower, typical, less macrofossiliferous Suwannee Limestone (Vicksburgian) that crops out along the Suwannee River, therefore, has always been correlated with the Chickasawhay which, in the past, was also considered to be Vicksburgian.
As can be seen, there is ambiguity between the earlier stratigraphic terminology of the Oligoceneand the modem terminology. If one reads the older terminology and correlations in the modem sense, they may appear to be consistent with modem usage but to do. so will often lead to confusion and erroneous correlation.
The following macrofossils are present in the Suwannee Limestone in its type area:
Clypeaster rogersi (?) Rhycholampas gouldii
Clypeaster rogersi has been reported from the Marianna Limestone, Mint Spring Formation, Glendon Limestone, and ByramFormationinMississippi (MacNeil and Dockery, 1984, p. 19), and from the Mananna and Glendon Limestones inAlabama (Cooke, 1926). Clypeaster rogersi also occurs commonly in the Marianna Limestone at Hawkinsville in Pulaski County, Georgia (Pickering, 1970). Rhyncholampasgouldiihas beenreported from the Mint Spring Formation and Marianna Limestone in Mississippi (MacNeil and Dockery, 1984, p. 19), but has not been reported from Alabama. Neither C. rogersi nor R. gouldii have been reported from the Chickasawhay Formation or Paynes Hammock Sand of Mississippi and Alabama.
Chlamys anatipes has also been reported from chert derived from Suwannee Limestone in northern Screven County, Georgia (Cooke, 1943, p. 84). Kuphus incrassatus, believed to be the calcitic burrow-lining tube of the boring bivalve Teredo, commonly is found in the upper part of the Suwannee Limestone in outcrop along the Withlacoochee River in Lowndes County, Georgia, Madison and Suwannee Counties, Florida, and in cores from Brooks, Thomas, and Colquitt Counties, Georgia.
Chlamys anatipes has been reported from the Forest Hill Formation, Mint Spring Formation, Marianna Limestone, and Glendon Limestonein Mississippi (Glawe, 1974; Dockery, 1982), and from the Red Bluff Clay, Marianna Limestone, Glendon Limestone, and Byram Formation in Alabama (Cooke, 1926; Glawe, 1974, Dockery, 1982). It is also found in the Bumpnose Limestone in Florida (MacNeil, 1944c, p. 1324; Moore, 1955, p.

38, 41; Glawe, 1974) and the Marianna Limestone in Georgia (Glawe, 1974). Chlamys anatipes is also found in the Florala Limestone in Alabama, and in the Bridgeboro Limestone in Georgia. Chlamys anatipes has not yet been reported from the Chickasawhay Formation or Paynes Hammock Sand of Mississippi and Alabama.
Kuphus incrassatus has most commonly been reported from the Chickasawhay Formation of Mississippi and Alabama. Kuphusincrassatus,however,isalsopresent in the Red Bluff-equivalent carbonate deposits in southwestern Alabama, and in the lower Miocene Chipola Formation of western Florida. Although the Chickasawhayan appears to represent a peak zone of K. incrassatus, its temporal range is more extensive than once thought and it can no longer be used for precise correla:tion.
On the other hand, the common occurrence of K. incrassatus at the top of the Suwannee Limestone section in southwestern Georgia and in the Withlacoochee River area of Georgia and Florida, may indicate that an unrecognized, overlying formation of younger Oligocene age may be present in that area. These sediments differ from typical Suwannee lithologies and reflect even shallower water conditions than that of typical Suwannee Lime.. stone.
The few macrofossils of the Suwannee Limestone with reasonably established ranges are restricted to the Vicksburgian of the eastern Gulf Coastal Plain. It is, therefore, concluded in this report that the best estimation of the age of the Suwannee Limestone in its type area along the Suwannee River in Florida, and in Georgia, is Early Oligocene, Vkksburgian (Rupelian). Because other Vicksburgian formations underlie the Suwannee Limestone, because the Suwannee occurs at the top of the local Oligocene stratigraphic section, because the Okapilco Limestone in the Gulf Trough contains a younger, Bucatunna planktonic foraminiferal suite, and because the Suwannee grades laterally into the Lazaretto Creek Formation that contains the planktonic foraminiferal plexus of Globorotalia increbescens-Globigerinaampliapertura that most resembles that of the Byram Formation of Mississippi, the Suwannee Limestone is correlated in this report with the upper Vicksburgian, Byram Formation. On that basis, the Suwannee Limestone would be included in the Cassigerinella chipolensis-Pseudohastigerina micra Zone of Stainforth and others (1975), and in Zone P19 of Blow (1969),{Pl. 1). For a listing of Suwannee smaller benthic foraminifera, see Horowitz (1979).
ATLANTIC CONTINENTAL SHELF STRATIGRAPHIC ASSOCIATION
LAZARETTO CREEK FORMATION (new name)
Definition The name Lazaretto Creek Formation is pro-
posed here for calcareous sand, sandstone and sandy

77

limestonein the shallow subsurface ofthe northerncoastal ers, 1987).

area of Georgia, from Glynn County in the south to

Macrofossils are rare and are known to consist

Chatham County in the north. The Lazaretto Creek only of mollusks. Where present, the macrofossils occur

Formation was referred to as "undifferentiated Oligo- . in concentrations of molds and casts in the sandstone or

cene" in ChathamCountyby Furlow (1969, p. 14-15), and limestone.

the narrie Lazaretto Creek Formation was informally

In cores, the sediment has the appearance of

applied by Huddlestun (1981) and Hetrick and others being massive-bedded with no distinct primary sedi-

(1987).

mentary or biogenic structures. Stratification, where

evident, is rude and ill-defined.

Type Section

Stratigraphic Relationships

The name Lazaretto Creek is taken from the tidal

creek, Lazaretto Creek, which separates McQueens Is-

The Lazaretto Creek Formation is known to oc-

land from Tybee Island in the coastal area of Chatham cur only in the northern coastal area of Georgia (Fig. 34).

County, The Lazaretto Creek Formation is a subsurface It grades laterally westward into the Suwannee Lime-

unit and the site of the Georgia Geologic Survey core stone but it pinches out southward and northward. There

Chatham 11 (GG5-1393)isheredesignated the type local- are no Oligocene deposits in the southern coastal area of

ity of the formation (Fig. 32). The location of the core site Georgia and eastern Florida, nor in the lower Port Royal

of Chatham 11 is approximately 1 airline mile (1.6 km) Sound area of South Carolina. It is not known whether

southeast of the US 80 bridge over Lazaretto Creek on the Lazaretto Creek Formation grades laterally eastward

Tybee Island, on the highway right-of-way of a county under the continental shelf into the Cooper Formation or

road 0.6 mile (1.0 km) south of the junction of the county ifit pinches outunder the innercontinental shelf. Because

road with US 80. The unit-stratotype (holostratotype) of the Lazaretto Creek Formation either grades laterally

the Lazaretto Creek Formation occurs in the ihterval126 into relatively pure limestones or pinches out, and it

feet to 196 feet in the core Chatham 11 (GG5-1393) (Fig. overlies relatively pure carbonates (Ocala Limestone),

33). The core Chatham 11 (GG5-1393) is stored at the the source ofquartz sand for the formation is problemati-

Georgia Geological Survey in Atlanta, Georgia.

cal. It must, however, have been derived from the north,

The site of the core Petit Chou 1 (GG5-1164) is possibly via southward flowing continental shelf cur-

here designated a reference locality of the formation. The rents flowing along the trend of the Beaufort Arch. There

Petit Chou 1 was taken on the beach near the western end are no other Lower Tertiary quartz sand sources for the

of Petit Chou Island (also known as Beach Hammock Lazaretto Creek Formation to the east, south, or west.

Island) in Chatham County (Fig. 3). The parastratotype

The Lazaretto Creek Formation generally over-

section of the Lazaretto Creek Formation occurs in the lies the Ocala Limestone disconformably. Where the

interval159 feet to 215 feet in the core Petit Chou 1 (GG5- Lazaretto Creekgrades laterally into the Suwannee Lime-

1164). The core is stored attheGeologyDepartment ofthe stone, it also locally overlies the Suwannee conformably

University of Georgia in Athens, Georgia.

and gradationally (Pl. 4). No lithologies are known that

are transitional from Suwannee to Lazaretto Creek. The

Lithology

Lazaretto Creek :.is disconformably overlain by the

Parachucla Formation.

The lithology of the Lazaretto Creek Formation

The Lazaretto Creek Formation is distinguished

ranges from an unconsolidated, incoherent, calcareous from the Ocala Limestone, Suwannee Limestone and

quartz sand; to a soft, friable, very calcareous quartz Cooper Formation in being consistently sandy and lo-

sandstone; to a friable, moderately indurated to uncon- cally phosphatic. The Parachucla Formation differs from

solidated, sandy, fine- to medium-grained, calcarenitic the Lazaretto Creek in being lithologically more variable,

limestone. Subordinate lithic components include clay in being more argillaceous, and in consistently being

minerals, phosphate in the form of small pellets or grains, more phosphatic. Over short intervals of core, however,

and glauconite. The pelletal phosphate is the most con- the lithology of the Lazaretto Creek closely resembles the

spicuous subordinate component of the lithology but is lithology of the Parachucla, and distinguishing the two

known to occur in only local and minor concentrations. formations may be difficult. However, there is generally

Phosphate is most conspicuous in the more sandy phases a prominent disconforrnity between the two formations

of the formation. Both glauconite and clay are very in which the uppermost Vicksburgian and

inconspicuous in the Lazaretto Creek Formation and the Chickasawhayan are missing.

clay is known to occur only interstitially and in low

In Chatham County, the Lazaretto Creek

concentrations. The clay minerals that have been re- Formtion ranges from 56 feet (17m) thick in the Petit

ported include smectite and kaolinite (Hetrick and oth- Chou 1 (GG5-1164) to 70 feet (21 m) thick in the Chatham

76

,'

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f

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Figure 33.

The type locality of the Lazaretto Creek Formation (U.S. Geological Survey, Beaufort, South Carolina-Georgia, 30 X 60 minute series, and Wassaw Sound, Georgia, 30 X 60 minute series [topographic-bathymetric quadrangles]).

79

CHATHAM 11

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Figure34.

The measured holostratotype of the Lazaretto Creek Formation.

80

N
t
Locality
Atlantic Ocean

Gulf of Mexico
DIXIE

0 10 20 30 40 50
H E3 H

miles

Figure35.

The areal distribution (subcrop) of the Lazaretto Creek Formation in Georgia.

81

11 (GGS-1393). It averages approximately 60 feet (18 rn) in thickness in Chatham County. The thickness distribution of the Lazaretto Creek Formation in the coastal area south of Chatham County is unknown due to lack of core control. It is present in the U.S. Geological Survey test wellS (GGS-1063) from Brunswick in Glynn County but its occurrence is not apparent from well log descriptions of Herrick (1961) in coastal Bryan, Liberty, Mcintosh, and Chatham Counties.
TheLazaretto CreekFormation was deposited in relatively shallow water on the continental shelf. The foraminiferal assemblage of the Lazaretto Creek is suggestive of inner neritic conditions under approximately normal marine salinities. In general, the benthic foraminiferal fauna of the Lazaretto Creek is less diverse and shows higherspeciesdominance than does the Suwannee foraminiferal fauna (for a listing of Suwannee foraminifera, see Horowitz, 1979). This suggests that the Lazaretto Creek Formation may have been deposited in shallower water than that of the Suwannee Limestone.
Age
The Lazaretto Creek Formation is interpreted to be late Vicksburgian, Rupelian, Early Oligocene in age. The Lazaretto Creek Formation contains a meager planktonic foraminiferal suite that consists of the following:
Globorotalia increbescens Globigerina ampliapertura.
. Globigerina eocaena
The occurrence of G. increbescens in the Lazaretto Creek indicates the formation is within the Cassigerinella chipolensis-Pseudohastigerina micra Zone of Stainforth and others (1975). In addition, the presence of well developed and moderately common G. ampliapertura relative to G. increbescens is characteristic especially of the upper Vicksburgian Byram Formation in Mississippi. Therefore, because G. increbescens and G. ampliapertura are not presentin_the Bucatunna Clay orthe Okapilco Limestone, both of which are of Vicksburgian age, the Lazaretto Creek Formation is correlated with the Byram Formation (Pl. 1). The presence of the above three species in the Lazaretto Creek formation could be construed to indicate a latest Eocene age for the Lazaretto Creek. However, the presence of the benthic foraminiferal species Pararotalia byramensis and P. mexicana requires an Oligocene age for the formation).
COOPER FORMATION
Definition The Cooper Formation, part of which is Oligo-
cene in age, is restricted to the continental shelf in the

Georgia area, and consists of massive and structureless, generally unconsolidated, finely to very fin.ely granular and even-textured, rnicrofossiliferous, variably argillaceous limestone.
The name Cooper was originally applied to calcareous deposits cropping out along the Cooper and Ashley Rivers in SouthCarolinaby Tuorney (1848). Sloan (1908, p. 462-464) referred to the Cooper variably as "Ashley-Cooper marls," "Cooper River marl," "Cooper marl,", and "Ashley marl," and to the marl cropping out along the Ashley River as Ashley Marl. He believed the Ashley and Cooper marls to be lithologically. similar enough to be combined under the name Ashley-Cooper marl. Sloan noted, however, that the "Ashley marl" tended to be more phosphatic than the "Cooper marl." In addition, (Sloan, 1908, p. 463) suggested that the marl along the Cooper River is of Eocene age whereas he suspected that the marl along the Ashley River might possibly be of Oligocene age. Cooke (1936, p. 82-89) simplified the stratigraphic terminology by recognizing only the name Cooper Marl, noting, however, that the upper part of the formation is more phosphatic than the lower part.
In the Georgia area, the Cooper Formation is present onlyunder the continental shelf and ranges inage from Late Eocene (late Jacksonian) to Early Miocene (Aquitanian). The Miocene component of the Cooper Formation beneath the continental shelf of Georgia was described previously by Huddlestun (1988) and the description of the Cooper Formation in this report will be restricted to the Oligocene portion of the formation. In contrast to the Oligocene sections onshore in Georgia, both Lower and Upper Oligocene (Vicksburgian and Chickasawhayan) componentsofthe Series are presentin the TACTS cores and in the USGS core AMCOR 6002. In these cores, the lithologies of the Early Oligocene, Vicksburgian; Late Oligocene, Chickasawhayan; and the Miocene parts of the Cooper Formation differ somewhat as will be described below.
Type Section
The name Cooper is derived from the Cooper River north of Charleston in South Carolina. No specific type locality was ever designated for the Cooper Formation along the Cooper-river, nor has the Cooper outcrop area along the Cooper River (or the Ashley River) been clearlydelineated (compare with Cooke, 1936,p. 87,pl.2). According to Ward (pers. corn., 1991) and Ward and Blackwelder (1979, p. 14), the Cooper Formation along the Cooper River is poorly exposed and the sediments are poorly preserved. Ward and Blackwelder (1979, p. 14) proposed that the section of Cooper Formation exposed in the quarry of the Giant Portland Cement Company near Holly Hill, Dorchester County, South Carolina, be

82

the lectostratotypeoftheformation and they changed the sense of the formation from Cooper Marl to Cooper Formation. In addition, they (1979, p. 14) designated the exposuresoftheCooperFormationinthebluffatGivhans Ferry State Park on the left bank of the Edisto River in DorchesterCountyasa referencesection(hypostratotype).
For reference purposes, the Oligocene component of the Cooper Formation under the continental shelf of Georgia occurs in the interval from approximately 289 feet to approximately 508 feet in the core AMCOR 6002 (Hathaway and others, 1976, p. 29-38)(Fig. 2).

Lithology

In the Georgia area, the Cooper Formation is

known to occur only under the outer continental shelf in

theTACTScoresandin the USGS core AMCOR6002. The

following lithologic descriptions are only for the Oligo-

cene part of the formation in these cores. With the small

amount of data available from these cores, the Oligocene

Cooper Formation on the outer shelf of Georgia can

tentatively be subdivided into three parts, based on a

progressive subtle change in lithology through the Oligo-

cene. These stratigraphic intervals include a lower

Vicksburgian component, a locally occurring uppermost

Vicksburgian component, and a Chickasawhayan com-

ponent. Generally the Oligocene Cooper Formation con-

sists of olive-gray, massive, structureless, even-textured,

finely to very finely granular, finely macrofossiliferous

(macrofossil debris), microfossiliferous, unconsolidated

and soft to slightly recrystallized and crumbly, variably

argillaceous limestone or "marl". Calcite or limestone is

the predominant lithic component of the formation

whereas clay minerals are variably minor to trace compo-

nents of the lithology. The clay mineral suite of the

Oligocene part of the Cooper Formation in the AMCOR

6002 is dominated by smectite with subordinate illite and

kaolinite (J.H. Hetrick, pers. com., 1985). Other minor to

trace componentsofthe CooperFormation include phos-

phate, glauconite, and silt or fine-grained quartz sand.

Pyrite, heavy minerals, mica, and gypsum occur as trace

components in some samples.

The lower, Vicksburgian component of the Coo-

per (Cassigerinella chipolensis-Pseudohastigerina micraZone)

is slightly phosphatic and glauconitic. It is largely a

foraminiferal coquina to foraminiferal coquinoid "marl"

but other bioclastic components are conspicuous. These

consist of fine bioclastic debris that includes echinoid

fragments, ostracodes, mollusk shell fragments, bryozoa,

and barnacles.

-

Phosphate is present in most samples and occurs

in the forms of vertebrate bone debris, shiny ovoid pel-

lets, and more irregular, rough-surfaced, subrounded to

rounded pellets that range in color from amber to tan

through brown to black. All pelletal phosphate ranges

from less than 1 mm to very fine sand size. Glauconite and pyrite more commonly occur as trace components but are not apparent in all samples.
Quartz sand is also present in most samples and, in one sample from the core nearest to the coast (A-237), constitutessomewhatlessthanonehalfofthebulksample. The sand in A-237, however, is poorly sorted, wellrounded to subangular, and medium- to coarse-grained. In other samples, quartz sand occurs as fine- to very fine grained sand in minor to trace amounts.
The upper-most Vicksburgian, Bucatunna-
Okapilco-equivalent (probable Globigerina ampliapertura
Zone) was detected in two samples, F-329 and C-253. Although two samples (or even two sections) are inadequate to define any stratigraphic patterns, the lithologies ofboth of the samples differ significantly from that of the older Vicksburgian and these differences may reflect the evolving depositional environment of the outer shelf. In sample F-329, the sediment consists of an argillaceous, phosphatic limestone or "marl" with gypsum bloom and scattered fine to very fine quartz sand. The sediment is exceptionally phosphatic and the washed residue may be described as phosphatic, foraminiferal coquina. The phosphate consists of both pellets and vertebrate debris. In C-253,on the otherhand, the sedimentisnotexceptionally phosphatic but the lithology is conspicuously dominated by foraminifera as in the Upper Oligocene.
The Upper Oligocene, Chickasawhayan is represented by five samples and represents a continuation of the evolving lithologies of the Cooper Formation. Of the fivesamples,however,three(C-223.5,C-204,andAMCOR 6002 sample 11.2) are represented by typical Cooper "marl" whereas sample B-300 is a clay and Sample D322.5 is a medium to coar~ sand.
Sample B-300 consists of a light olive gray (5Y5I
2), massive and structureless, silty, calcareous, phosphatic, foraminiferal clay. The washed residue consists of a foraminiferal, phosphatic, fine- to very fine grained quartz sand. The phosphatic component is common and consists of vertebrate skeletal debris and pelletal phosphate that is subrounded to subangular, and amber to dark brown in color.
Sample D-322.5 consists of light olive gray (5Y5I
2), massive and structureless, calcareous, phosphatic, clayey sand with phosphate pebbles. The washed residue consists of calcareous, phosphatic sand. The sand component is poorly sorted, very coarse (well-rounded) to very fine (angular); the largest sand grain size is roughly 1 mm. In the coarser fractions, the phosphate component consists of poorly sorted phosphate pellets and pebbles up to.l c~ in greatest dimension. The finer fraction consists ofvertebrate skeletal debris, tan to brown to black pellets, and some shiny ovoidal pellets. The calcareous fraction consists mostly of foraminifera and nondescript calcitic particles. Foraminifera and echinoid

83

spines are rare in the coarser fraction but are mqre common in the finer fractions. Glauconite, pelletal phosphate, and heavy minerals also are more common in the finer fractions.
With five samples, it is difficult to generalize on the lithostratigraphy of the Upper Oligocene component of the Cooper Formation in the TACTS area. However, three samples are compatible with the Cooper Formation whereas the other two samples are siliciclastic and phosphatic variants of the Cooper. In general, the Upper Oligocene is generally more siliciclastic-rich, phosphatic, and the foraminiferal sediment is coarser textured than the underlying Vicksburgian.
The difference between the foraminiferal coquina of the lower Vicksburgian Cooper compared with that of the upperVicksburgianCooperand the Chickasawhayan Cooper is that there is declining micrite and fine, broken macrofossil debris upward through the section. This trend culminated in the Upper Oligocene and Miocene. As a result, the Upper Oligocene Cooper is more coarsely granular in texture and conspicuously foraminiferal whereas the Vicksburgian Cooper is finer grained and tends to be more chalky when dry.
Stratigraphic Relationships
The Cooper Formation is restricted to the continental shelf in the Georgia area but is probably continuous northward with the onshore Cooper Formationin the Charleston area in South Carolina (Fig. 35, Pis. 4 and 5). The stratigraphic relationships of the Oligocene component of the Cooper Formation with the Georgia onshore Oligocene section are uncertain however. Because there are no Oligocene deposits present in the coastal area of Georgia south of the vicinity of Brunswick in Glynn County, I must conclude that both the Lower and Upper Oligocene parts of the Cooper Formation thin westward and pinch out under the inner continental shelf in that area (Pl. 5). In the northern coastal area of Georgia, north of the vicinity of Brunswick, the Upper Oligocene, Chickasawhayan component of the Cooper Formation likewise thins and pinches out under the inner continental shelf (Pl. 3). The Lower Oligocene, Vicksburgian component, on the other hand, appears to grade laterally westward into the Lazaretto Creek Formation under the inner continental shelf (Pl. 4). The southern limit of the Cooper Formation on the continental shelf is unknown at this time.
The Cooper Formation is distinguished from other limestone formations in eastern Georgia in consisting of light olive gray, finely equigranular, microfossiliferous, phosphatic, argillaceous limestone ("marl") whereas the other limestone formations in the area are non-argillaceous and more coarsely granular to bioclastic in texture. The Lazaretto Creek Formation is

also sandy and locally phosphatic, and the Miocene Parachucla Formation in the coastal area is sandy, argillaceous, phosphatic, variablymacrofossiliferous, and locally dolomitic. Under the outer continental shelf, the lower Aquitanian (lower Parachucla equivalent) component of the Cooper Formation is consistently more siliciclastic-rich and more phosphatic.
The thickness distribution of the Oligocene component of the Cooper Formation under the continental shelf is variable. It is approximately 186 feet (57 m) thick in AMCOR 6002, is at least 145 feet thick in TACTS core C, but is only approximately 30 feet thick in TACTS core A). The environment of deposition of the Oligocene component of the Cooper Formation is marine, outer neritic, continental shelf.
Age
All oftheages of the Oligocene deposits that have beenidentified at onshore sitesin the southeasternUnited States, have also been identified in the Oligocene component of the offshore Cooper Formation. The oldest Oligocene interval is the Cassigerinella chipolensisPseudohastigerina micra Zone of Stainforth and others (1975)orZonesP18toP19ofBlow(1969). Thisplanktonic foraminiferal zone has been identified in the interval327 feet to 508 feet in the AMCOR 6002, 220 feet to 250 feet in TACTScoreA, and 261 feet to T.D. at336 feet in TACTS core C. The age assignment is based on the identifications of the following planktonic foraminifera:
Globorotalia increbescens Globigerina ampliapertura
c;. eocaena
G: angiporoides G. officinalis G. praebulloides G. cf. ciperoensis Globorotaloides suteri Pseudohastigerina barbadoensis Cassigerinella chipolensis Chiloguembelina cubensis
This zone is present throughout most of the onshore Vicksburgian and includes the Bumpnose Limestone-Red Bluff Clay stratigraphic interval through the Suwannee-Byramstratigraphicinterval(Pl.l). Theageof this portion of the Cooper Formation is, therefore, considered to be Early Oligocene, Vicksburgian (Rupelian).
The latest Vicksburgian, Bucatunna-equivalent has been identified in the interval of approximately 235 feet to 265 feet in the TACTS core C and approximately 325 feet to T. D. at 336 feet in TACT'S core F. This correlation is based on the identifications of the following

84

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t

TAYLOR
FRANKUN
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~ Gulf of Mexico

0 10 20 30 40 50
E3 E3 H

miles

Figure36.

The areal distribution (subcrop) of the Cooper Formation beneath the continental shelf of Georgia.

85

planktonic foraminifera:
Globigerina eocaena G. officinalis G. praebulloides G. anguliofficinalis G. cf. ciperoensis Chiloguembelina cubensis
The above correlation is based on the absence of
Globorotalia increbescens and Pseudohastigerina spp. which became extinct near or at the top of the Cassigerinella chipolensis-Pseudohastigerina micra Zone, and the absence of Globigerina angulisuturalis which evolved within the lower part of the Globorotalia opima opima Zone (Pl. 1). As
a result, this stratigraphic interval is tentatively assigned
to the Globigerina ampliapertura Zone of Bolli (1957),
Stainforth and others (1975), and Zone P20ofBlow (1969). The Upper Oligocene, Chickasawhayan interval
hasbeen identified in the interval289 feet to 327feet in the AMCOR6002(sample11-2,9Q-100cm),approximatelyin the interval295 feet to T.D. at300 feet in theTACTScore B, approximately 193 feet to 235 feet in TACTS core C, approximately 310 feet to T.D. at 323 feet in TACTS core D,andapproximately319feettoT.D.at330feetinTACTS core F. This age assignment is based on the following planktonic foraminifera:

phosphatic and cherty calcareous sand, sandy limestone, limestone, and "marl". Itis restricted in occurrence to the northeastern part of the Gulf Trough area. (Fig. 36). The unit is poorly defined because 1) it is not known to crop out, 2) there are no. cores from its area of occurrence, and 3) its lithology can be approximated at this time only through descriptions of well-cuttings (Herrick, 1961; McFadden and others, 1986). However, well-cuttings of Oligocene sediments from most sites in updip eastern Georgia, centered in the central Ohoopee River area, are consistently reported to be sandy and variably "marly", cherty and phosphatic. As a result, these Oligocene sediments can not be included in other named Oligocene limestone formations of Georgia and must, therefore, be described separately. The undifferentiated sand and sandy limestone does resemble the Lazaretto Creek Formation of the coastal area. However, Lazaretto Creek lithology is not apparentin the well logs of Herrick (1961). In addition, there is no consistent occurrence of phosphatic, sandy Oligocene sediments between the upper Gulf Trough area in Montgomery and Toombs Counties, Georgia, and the coastal subcrop area of the Lazaretto Creek in Georgia. Finally, it is not clear whether this undifferentiated calcareous sand consists of one formation or more than one formation.
Lithology

Globigerina angulisuturalis G. eocaena G. praebulloides G. ciperoensis Cassigerinella chipolensis Chiloguembelina cubensis
Theabove planktonic foraminiferal assemblageis consistent with Zones P21 or P22 of Blow (1969) and with the
Globorotalia opima opima zone or Globigerina ciperoensis
Zone of Bolli (1957) and Stainforth and others (1975). The assemblageofplanktonic foraminifera is similarto that of the Chickasawhay and Paynes Hammock Formations of Alabama and Mississippi (Poag, 1966; 1972). As a result, this portion of the Cooper Formation is correlated with the Chicksawhay and Paynes Hammock Formations (Pl. 1).
STRATIGRAPHIC ASSOCIATION OF UNCERTAIN AFFINITIES
UNDIFFERENTIATED CALCAREOUS SAND AND SANDY LIMESTONE
Definition This undifferentiated Oligocene unit is a subsur-
face formation that consists variably of sporadically

Based on well-cuttings descriptions, the lithology of the undifferentiated calcareous sand and sandy limestone consists variably of calcareous sand and sandy limestone with lesser amounts of relatively pure limestone, "marl", and calcareous clay. The quartz sand ranges from fine-grained to very coarse grained, and the sorting ranges from well-sorted to poorly sorted. Minor lithic components include phosphate, chert, glauconite, and rare claystone and mica. The deposits are generally but variably macro- and microfossiiiferous.
Stratigraphic Relationships
The undifferentiated calcareous sand and sandy limestone isknown to occur onlyin easternGeorgiain the northeasternpartof theGulfTrough and northwestof the trough (Fig. 36). Its known occurrence centers in Treutlen and Emanuel Counties but it is also found in Laurens, Wheeler, Montgomery, and Toombs Counties. There are scattered occurrences of the unit in northwestern Tattnall and western Candler Counties, and lithologically similar well-cuttings have been reported from Oligocene sediments at scattered sites from northern Bulloch County (McFadden and others, 1986).
The calcareous sand and sandy limestone unit appears to grade laterally southward and eastward into theSuwanneeLimestonein the vicinityoftheGulfTrough.

86

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... 3?.~
Atlantic ,,. Ocean

TAYLOR
of Mexico
DIXIE

0 10 20 30 40 50
H

miles

~

VOLUSIA

'l~

'-./'""-, r-

\j

Figure37.

The areal distribution (subcrop) of the undifferentiated calcareous sand and sandy limestone.

87

The unit into which the calcareous sand and sandy limestone grades into southwestward in the Gulf Trough is not clear at this time. If the calcareous sand and sandy limestone unit grades laterally into the Suwannee Limestone, then it is seems likely that within the Gulf Trough, the unit would grade laterally into the upper part of the Pridgen Limestone Member of the Ochlockonee Formation. Because the calcareous sand and sandy limestone is unusually thick in the eastern end of the trough, it is also possible that the upper part of the deposit may grade laterally southwestward in the Gulf Trough into the Okapilco Limestone.
The thickness of this sandy unit, based on published thicknessdata ofHerrick (1961),Herrickand Vorhis (1963), and McFadden and others (1986), ranges from approximately 30 feet (9.1 m) to 240 feet (73.2 m).
The environment of deposition of the undifferentiated calcareous and sandy limestone is marine, inner continental shelf. Considering the paucity of siliciclastics in Oligocene deposits in Georgia, Florida and South Carolina, the unusually large amount of siliciclastic material inthis undifferentiated unit suggests a nearby river source.
Age
The undifferentiated calcareous sand and sandy limestone is assigned an Early Oligocene, Vicksburgian (Rupelian) age because its known microfauna consists of characteristically Oligocene species, and it grades laterally into the Suwannee Limestone which is considered to be Early Oligocene, late Vicksburgian in age. The undifferentiated calcareous sand and sandy limestone contains the following benthic foraminifera, which are compatible with a Vicksburgian age:
Pararotalia mexicana P. byramensis Asterigerina subacuta Dictyoconus sp. Baggina xenoula

Huddlestun 1988) (Florida Plateau of Vaughan, 1910; Cooke, 1945) (Fig. 38) is that segment of the Coastal Plain that consists of peninsular Florida and its continental shelves. Basement of the Florida Platform consists of Paleozoic sedimentary rocks called the Suwannee terrane (Dallmeyer,1987),and plutonicigneous and metamorphic rocks that variously have been called African craton (Chowns and Williams, 1983),and African basement (Nelson and others, 1985a,1985b). For simplicity
in this report, the basementof the Florida Platform will
be called African basement (Andress and others, 1969; Goldstein and others, 1969; Cook and others, 1979; WilliamsandHatcher,1982;Smith,1982,1983;Mueller and Porch, 1983; Chowns and Williams, 1983; Nelson and others, 1985a, 1985b; Dallmeyer, 1987).
A thick Coastal Plain sequence of flat lying to gently dipping, shallow-water, carbonate bank and assciated deposits of Late Jurassic? through Early Tetiary age overlies the African basement in peninsular Florida. The northern boundary of the Florida Platform is the Georgia Channel System, north of which these shallow-water, carbonate bank sediments were not dposited. African basement in this region is not restricted to the Florida Platform. The Florida panhandle and southern Alabama west and north of theGeorgia ChannelSystem, andmuchoftheGeorgia Channel System also are underlain by African Basement (Suwannee basin of Arden, 1974).
South Georgia Rift
Overlying the African basement in western
Florida and Georgia is a thick sequence of Triassic-
Jurasic(?) red beds of fluvial, probably braided
stream origin (Chowns and Williams, 1983) that has
been asigned to undifferentiated Newark Group
(Huddlestun and others, 1988). These red beds were
deposited in a large Triassic graben called the South
Georgia riftbyDanieland others,1983 (also see Chowns
and Williams,1983;Popenoe and Zietz, 1977; Popenoe,
1987; Gohn and others, 1978; Chowns, 1979)(Fig. 39).

Because this UIJ.differentiated sandy unit is unusually thick in the Gulf Trough, it is possible that the unit is correlative with both the Ochlockonee Formation and Okapilco Limestone within the Gulf Trough.

DISCUSSION
PRIMARY STRUCTURAL ELEMENTS Florida Platform
TheFloridaPlatform6 (Owens,1960;Chen,1965;

~e Florida Platform probably should be considered as continuous with the Bahamas Platform as described by Owens (1960). Sheridan andothers (1981) indicatethatthedeeperMesozoicstrataarecontinuous from Florida to the Bahamas Platfrom: but the Florida-Bahamas Platform is bisected by the Northern Strait of Florida, a sedimentary constructional feature closely related in origin to the Georgia Channel System

88

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0 10 20 30 40 50

H

H

miles

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\../""", r-

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Figure38.

Proposed shallow structural elements controlled by basement structure in the Coastal Plain of Georgia and northern Florida.
89

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- - - - - -----1---,-~ /-----..\ ___ .... I

\\ ' \ " Alabama

...... __

',

Georgia

South Carolina

I

\
\

'\.. ' .....
-~, ..._......,r-r-r-

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ATLANTIC OCEAN

GULF OF MEXICO

Figure39.

The South Georgia rift from Daniel and others (1988).

90

This Triassic basin has also been referred to as the Main rift zone (Daniels and others, 1983), the South CarolinaGeorgia basin (Gohn and others, 1978), and the Tallahassee Graben (Opdyke and others, 1987). Two smaller grabens, the Riddleville basin and the Dunbarton basin, are associated with and north of the South Georgia rift. These Triassic grabens are similar to those farther north in the eastern United States except the South Georgia rift . and Riddleville basin are oriented in a more east-northeast direction than the northern Triassic grabens.
The origin of the Suwannee Strait and the Georgia Channel Systemare best sought inthe SouthGeorgia rift of Daniels and others (1983). The South Georgia rift may also be continuous with a similar Triassic-Jurassic(?) basin referred to as the Apalachicola basin (Klitgord and others, 1984) in the northeastern Gulf of Mexico. If the South Georgia rift remained mildly and intermittently active (subsiding) during the middle and Late Cretceous, then the presence and orientation of the fault-block basins would be sufficient to make them progenitors of the SuwanneeStrait during the Late Crtaceous. In this model, the origin of the coastal Apalachicola Embayment is the underlying Triassic-Jurassic(?) Apalachicola basin and the origin of the Suwannee Strait and Georgia Channel Sytem is the underlying South Georgia rift. Once the water depth in the SuwanneeStraithad become sufficient to permit large scale movement of water from the Gulf of Mexico into the Atlantic Ocean, the Suwannee Current and the Georgia Channel System were established.
Piedmont slope
The Piedmont Slope (Cramer and Arden, 1980, Fig. 3; Huddlestun, 1988, p. 13) is a loosely defined segment of the Coastal Plain in Georgia characterized by a structurally simple wedge of Coastal Plain sediments over a consistently southward to southeastward dipping crystalline basement (Fig. 38). The Piedmont Slope extends from the Fall line in the north to a poorly defined area in the south where a reduction in the dip of the basement occurs (compare with Maher, 1965, pl. 6; 1971, pl. 13). The slope change appears to be irregular but generally occurs along a trend from the southwestern corner of Georgia (the viCinity of Seminole and Decatur Counties), northeastward through Screven County (Pl. 2; compare withHerrickandVorhis, 1963,Figs.3,6, 10, 14, 16, 18). However, the slope change cannot be readily identified in Applin and Applin, 1967, pls. 4D, 4E, 6C). The Georgia Channel System occurs at the toe of the Piedmont Slope.
The stratigraphic and structural relationship between the Piedmont Slope and the Florida Platform is ambiguous because the postulated boundary between the slope and platform approximates the trend of the Georgia Channel System and is, therefore, obscured by

the overlying sedimentary constructional feature. The relationship of the Piedmont Slope to basement type and province is also not as apparent as that of the Florida Platform to African basement. However, the Piedmont Slope appears to be underlain by North American basement and the Paleozoic accreted terranes of Nelson and others (1985a, 1985b), and possibly by portions of disturbed or overthrust Africimbasement (Dallmeyer, 1987). It may be that the major distinction between the Florida Platform and Piedmont Slope is that the basement of the platformis relative.ly "homogeneous" whereas that of the slope is heterogeneous, and the boundary is a zone and not a line.
Peninsular Arch
The Peninsular Arch has in the past been considered to be a north-northwest--south-southeast trending arch or structural high that influenced only Cretaceous deposits in Florida (Applin, 1951; Toulmin, 1955; Puri and Vernon, 1964; Maher, 1965; Banks, 1976). In this report, the Peninsular Arch can be recognized in Georgia as far north as Ben Hill and Irwin Counties (Fig. 40)(compare with Maher, 1965, pl. 7). In Georgia the Peninsular Arch appears to have influenced the structural attitudes of deposits as late as the Claibornian (Huddlestun and others, in review) but in Florida its influence on deposits younger than the Cretaceous is not apparent (Applin and Applin, 1967; Maher, 1965, 1971). Additionally, the Peninsular Arch appears to have influenced depositional patterns in the region as young as the Oligocene because no pre-Suwannee deposits occur east of .the arch and all Oligocene deposits are absent along the crest of the arch in northern Florid'a.
The Peninsular Arch is a subtle structural feature in Georgia. The Georgia Channel System has overprinted much of the arch in southern Georgia so that its presence is difficult to detect. However, it can be identified as an arch on Plate 7 of Maher (1965) and in Figure 41, a stratigraphic cross section normal to the Peninsular Arch and paralleling the Gulf Trough. However, the Peninsular Arch appears to be more than simply a structural arch. Its influence on the Oligocene stratigraphy in the area suggests that it may also serve as a structural hinge between the Gulf of Mexico and Atlantic Coastal Plain. The extent of the Peninsular Arch thus appears to be greater and it appears to have persisted longer than previously thought.
There is evidence that the Peninsular Arch influenced the configuration of the latest Cretaceous-Early Paleocene Suwannee Channel and the later Gulf Trough. I suggest here that the Suwannee Saddle of Applin and Applin (1967) is a direct consequence of the Peninsular Arch; i.e., the Suwannee Saddle is a constriction that occurs where the channel crosses the arch (Fig. 40). As

91

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Gulf of Mexico
0 10 20 30 40 50 miles
H HH

Atlantic Ocean
VOLUSIA

Figure40.

The Peninsular Arch and related features in Georgia and northern Florida. 92

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~

Figure41.

Stratigraphic cross-section across the Peninsular Arch and paralleling the trend of the Gulf Trough from Dougherty County to Emanual County.

93

such, the Peninsular Arch divided the Tallahassee Embayment to the west from the Southeast Georgia Embayment to the east (Fig. 40). It is not known whether the floor of the Suwannee Saddle was shallower than the rest of the channel during the occupation of the channel by the Suwannee Current. If future studies indicate that it was, then the Peninsular Arch also could have formed a sill that acted as a blockage to the Suwannee Current during the terminal Midwayan low stand of the sea.
The Peninsular Arch also may have influenced the position of the Gulf Trough. The only feasible explanation for the dog-leg in the Gulf Trough in Colquitt, Tift, Cook, Berrien, and Irwin Counties, Georgia (Fig. 41), is that the floor of the Suwannee Strait was bathymetrically high along the axis of the Peninsular Arch during the Claibornian. This shallowing caused the Suwannee Current to veerslightly seaward into deeper water offshore of the shoal. This model can explain both bends in the trough, the western bend in Colquitt County where the shoaling began, and the eastern bend in Irwin County. Where the shoaling ended, the current appears to have resumed its northeastward flow. Thismay havebeen due to the Suwannee Current being dragged northeastward by the northward flowing water-masses of the paleoFlorida Current and paleo-Antilles Current merging off of Georgia to form the paleo-Gulf Stream (compare with Popenoe and others, 1987, Fig. 6).
CONSTRUCTIONAL FEATURES OF SEDIMENTARY ORIGIN
Georgia Channel System
As defined by Huddlestun and others (in manuscript), the Apalachicola Embayment, Chattahoochee Embayment, Tallahassee Embayment, Gulf Trough, and Suwannee Channel, are components of a system of sedimentary constructional features called the Georgia Channel System (Fig. 42). The Georgia Channel System was formed largely through nondeposition or diminished deposition under the axis of the Suwannee Current (seep. 110-112-), a Late Cretaceous through Early Tertiary com:. ponent of the western North Atlantic Ocean current system (Huddlestun and others, in manuscript). It is postulated here that the Suwannee Current and Georgia Channel System must have dominated or at least strongly influenced the sedimentary patterns, stratigraphy, and faunas of most of the Coastal Plain of Georgia from the Late Cretaceous (upper Tayloran or Navarroan to the Middle Miocene (lower Serravallian).
The Georgia Channel System is divided into two spatially and temporally separate but analogous channels. There is an older, Late Cretaceous (TayloranNavarroan) through Middle Eocene channel which consists of the Suwannee Channel with a southwestward

flaring component called the Tallahassee Embayment and an eastern component called the Southeast Georgia Embayment (Fig. 43)(Huddlestun and others, in manuscript). Second, there is a younger Middle Eocene to Middle Miocenecomponent that is called the GulfTrough and which hasa southwestward flaring component called the Chattahoochee Embayment (Fig. 44)(Huddlestunand others, in manuscript). The combined southwestward flaring Tallahassee and Chattahoochee Embayments are referred to collectively as the Apalachicola Embayment (Fig.42-44). The presence of the two spatially and temporally distinct channels is postulated to have resulted from a reduction and change in flow direction of the Suwannee Current during the Late Paleocene (early Sabinian). This usage differs from, but is compatible with, previous usage.
The distinction made here between the Chattahoochee Embayment and Gulf Trough is that proposed by Huddlestun and others (in manuscript). The Chattahoochee Embayment is the flaring southwestern part of the Gulf Trough (Fig. 44), which gradually narrows and shallows to the northeast. The Gulf Trough constitutes the entire channel, including the Chattahoochee Embayment, from at least the coastal area (and probably across the entire continental shelf of eastem panhandle Florida), northeastward to the vicinity of Candler County, Georgia. East of the Chattahoochee Embayment inColquitt County, Georgia, the GulfTrough is a roughly parallel sided, relatively narrow feature. In addition, the stratigraphy of the Chattahoochee Embaymentdiffers somewhatfrom thatoftheGulfTrough northeast of the er,nbayment. For the Oligocene, typical Ochlockonee Formation is confined to the Chattahoochee Embayment whereas the Pridgen Limestone Member of the Ochlockonee is present only in the parallel sided Gulf Trough to the northeast. The Wolf Pit Dolostone and Okapilco Limestone are largely confined to the parallelsided northeastern part of the trough and the interior of the Chattahoochee Embayment in Colquitt County and, perhaps as far southwest as Grady County. These formations are not known to be presentfarthersouthwest in the Chattahoochee Embayment.
This imperfect distinction between the Chattahoochee Embayment, Apalachicola Embayment, and Gulf Trough is at variance with past distinctions between the features. The Apalachicola Embayment generally has been believed to be an ancient, Jurassic to Miocene, westward to southwestward flaring, structurally subsiding feature that is largely confined to Florida (Murray, 1961; Schmidt, 1984). However, the southwestward flaring Suwannee Channel and Gulf Trough were pointed outby Huddlestun and others (in manuscript) to be temporally and, to a lesser extent, spatially distinct features. Therefore,Huddlestun and others (in manuscript) assigned two diffei'ent names for these embayments in the

94

N

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t

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Atlantic Ocean

Gulf of Mexico

fvlt'i.RION
. ---. -- -i

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Figure42.

Constructional features of sedimentary origin.

95

N
t

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32'

Atlantic Ocean

Gulf of Mexico

0 10 20 30 40 50 miles

H

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Figure43.

Reconstruction of the Suwannee Channel, Tallahassee Embayment, and Southeast Georgia

Embayment in Georgia and northern Florida.



96

N
t

Atlantic Ocean

Gulf of Mexico

DIXIE

LEVY

0 10 20 30 40 50 miles

H

E3 E3

Figure44.

Reconstruction ofthe GulfTroughand ChattahoocheeEmbayment in Georgia and northern Florida.

97

interest of precision in communication. Huddlestun and others (in manuscript) also concluded that there may be some utility in retaining the concept of the Apalachicola Embayment as the collective southwestward flaring feature of the channel system.
In Georgia, the entire channel system has been variously called the Suwannee Strait (Rainwater, 1956; Manker and Carter, 1987), Suwannee Channel (Chen, 1965; McKinney, 1984), or Gulf Trough (Herrick and Vorhis, 1%3; Sever and others, 1%7; Gelbaum, 1978; Gelbaum and Howell, 1982) whereas in Florida the system has generally been referred to as the Apalachicola Embayment, Suwannee Strait, or Suwannee Channel (see Huddlestun and others [in review] for a discussion of the usage ofthe terms). However, Huddlestun and others (in manuscript found that there are no valid distinctions in the channel system on either side of the Florida-Georgia state line.
The general morphologies of the Gulf Trough and SuwanneeChanneldiffer somewhat. TheGulfTrough (Fig. 44) flares southwestward southwest of Tift County (Chattahoochee Embayment) and, other than two minor bends in the channel, it remains relatively straight, narrow and parallel sided until it shoals and merges with the continental shelf in eastern Georgia. The Suwannee Channel has a different morphology. The Tallahassee Embayment (Fig. 43) flares to the west and is narrowest where it crosses the Peninsular Arch in the LowndesEchols County area in Georgia. The Southeast Georgia Embayment opens eastward from there.
Based on data presented here, the time span of the Suwannee Channel was Late Cretaceous (late Tayloran) through Middle Eocene (Claibornian) with channel-infillingoccurringfrom LatePaleocene (Sabinian) through Middle Eocene (Claibornian)(also see Hull, 1962). The time span of the Gulf Trough was from the middle to late Middle Eocene (Claibornian) to Middle Miocene (earlySerravallian)withchannel-infillingoccurringfrom the Oligocene (Vicksburgian) into the Middle Miocene (Serravallian)(see Plates 2, 3, 5)(Huddlestun and others, 1988).
The Gulf Trough originated with the northwestward migration of the carbonate depositional province on the Florida Bank to the southern margin of the Suwannee Current during the middle Claibornian (Huddlestun and others, in manuscript). This expansion of the carbonate province resulted from a decrease in siliciclastic input to the continental shelf from the continent. Because current velocities would decline on either side of the Suwannee Current, skeletal sediment accumulationand upbuildingofthecarbonateshelfbottomwould occur away from the current. In contrast, there was reduced sedimentation or nondeposition under the current (resulting in relatively deep water conditions). Once the channel margins were constructed in this manner, the

current was locked in place and could not migrate laterally.
The Gulf Trough reached its greatest development and depth near the end of the Eocene when topographic relief in the vicinity of the trough may have been as much as 600 feet in southwestern Georgia (Huddlestun and others, in manuscript). Diminished volume of the Suwannee Current and diminished current velocity at the end of the Eocene raised the base level of sedimentational equilibrium on the floor of the Gulf Trough. Thus channel-infilling was initiated at the end of the Eocene and beginning of the Oligocene (Fig. 45).
Southeast Georgia Embayment
The Southeast Georgia Embayment was considered by Huddlestun and others (in manuscript) to have originated as the eastward flaring component of the Suwannee Channel (Fig. 43)(compare with Pinet and Popenoe,1985). Thatis,itoriginated throughnondeposition on the continental shelf under the massive Suwannee Current. Therefore, they concluded that the latest Cretaceous and Tertiary Southeast Georgia Embayment was not so mucha result ofbasement tectonics and differential subsidence, but of sedimentary processes. This is consistent with the observation of Maher (1965) where he considered the Southeast Georgia Embayment to be a passive structure. Subsequent to the massive reduction in the Suwannee Currentafter the Midwayan, theSuwannee Channeland its eastern component, the Southeast Georgia Embayment, became a depocenter on the continental shelf. By the end of theMiddleEocene, muchoftheonshorepartoftheSuwannee. Channel had been filled with sediment. As a result, Upper Eocene and Oligocene deposits in eastern Georgia do not reflect the presence of the Southeast Georgia Embayment and they are uniformlyand relatively thin across the region. The Miocene "depocenter" in the Southeast Georgia Embayment was a.scribed by Huddlestun ahd others (in manuscript) to deep entrenchment of the paleo-Altamaha River system during the Late Oligocene low stands of the sea.
Beaufort Arch
The Beaufort Arch (Heron and Johnson, 1966, p. 54; Huddlestun, 1988, p. 15) is a low, broad, structural high trending south-southwestward from Beaufort County, South Carolina, onto the continental shelf off Georgia (Fig. 41). The Beaufort Arch is present on-shore in Georgia only in eastern Chatham County. South of Chatham County, the Beaufort Arch occurs only on the inner continental shelf and has been traced as far south as offshore Cumberland Island (Woolsey, 1976, p. 56, Fig. 3; Foley, 1981, p. 48-49, Fig. 20).
Huddlestun (1988) thought that the Beaufort Arch

98

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did not exist prior to Miocene time and, therefore, was a Neogenestructural element. However,subsequentwork (Huddlestun and others, in manuscript) has shown that the BeaufortArch can be traced on structural contours on the top of the Eocene but not on the tops of any older horizons in the area. In addition, the only known occurrences of the shallow-water, sandy Lazaretto Creek Formation of Vicksburgian age are on, and in the vicinity of, the Beaufort Archin Chatham and GlynnCounties, Georgia. This suggests that the Beaufort Arch influenced sedimentation patterns during the Early Oligocene. Because the Beaufort Arch cannotbe recognized prior to the Upper Eocene; it is concluded that the arch may have formed as a result of differential carbonate shelfsedimentation. That is, the Beaufort Arch represents a linear area where Late Eocene sedimentation rates were relatively high compared with the surrounding continental shelf. Therefore it is concluded that the Beaufort Arch is not a structural feature related to basement tectonics but is probably associated with differential sedimentary processes on the continental shelf during the Late Eocene.
Ocala Arch
The Ocala Arch (Fig. 42) is a structural high that in Florida is also reffered to as the Florida Platform (pers. com., T. Scott, 1992). For discussion, see Huddlestun, 1988, p. 13-15). Huddlestun (1988) reasoned that if tectonic upliftoccurred on the arch, it must havebeen minor, and that the major structural movement associated with the "arch" was subsidence on the flanks of the Peninsular Arch. Winston (1976) also denied the uplift model of the Ocala Arch and he described the structure as a ''blister dome". Winston (1976, p. 993) observed that the:

outcrop pattern of Oligocene and older formations in northwestern peninsular Florida. On this basis, the Ocala Arch can be identified as far northwest as the lower Withlacoochee River in southern Brooks and Lowndes Counties, Georgia. The occurrence of karst terrain in southern Lowndesand Brooks Counties also results from the presence of th(i! Ocala Arch.
HYPOTHETICAL STRUCTURES
Chattahoochee Arch
For a comprehensive survey of the history of the name Chattahoochee Arch (also referred to as Chattahoochee uplift and Chattahoochee anticline), see Patterson and Herrick (1971). TheconclusionsofPatterson and Herrick (1971, p. 13-14) concerningtheChattahoochee Arch are as follows:
So many different ideas on the location and extent of the Chattahoochee Anticline have been published... without supporting evidence that anyone who reviews them has difficulaty indistinguishing the imagined from reality. Accordingly, interpretations of this feature, presented without evidence, should 'De considered as no more than hypothetical. Sufficient geologic evidence is now available to conclude tfiat the original proposal of the existence of this anticline by Veatch and Stephenson (1911), and the redifinition by Sever (1965) should be considered invalid.

...direction of thickening in all formations is southwestward, and the rate of thickening in all units except the Lake City is fairly constant. In the Lake City, the rate of thickening increases abruptly.... beneath the crest of the Ocala feature, then return to normal farther southwest....
Winston (1976) interpreted the arching of the Ocala feature to be the result of the initial uniform dip to the southwest and anabrupt thickening of the Lake City Formation. The "arch" was formed later by subsidence and tilting of the continental margin to the east or northeast. As such, the Ocala Arch is not a true structural arch; it has the geometric appearance of an arch in the upper part of the geologic section but not in the lower part of the geologic section or basement (see Winston, 1976, Figs. 3 and 4). In addition, the Ocala Arch cannot be separated from the Peninsular Arch on Plate 8 of Maher (1965).
The trend of the Ocala Arch can be traced by the

In the present study, I must conclude that the opinion ofPatterson and Herrick (1971) is correctand that the Chattahoochee Arch (or uplift or anticline) exists neither as a real nor apparent structural feature. The concept of the Chattahoochee Arch is rejected here based on three lines of evidence. First, if the Chattahoochee Arch were a true positive element (i.e., defined either by uplift along the crest of the structure or by subsidence in adjacent areas), it should stand outprominently on structural contour maps on deeper stratigraphic horizons. No such significant structural relief can be observed on the top of the pre-Upper Cretaceous, base of the Austinian, top of the Tayloran, top of the Cretaceous, top of the Paleocene-Lower Eocene, top of the Middle Eocene, or top of the Upper Eocene in the eastern panhandle of Florida or southwestern Georgia (Applin and Applin, 1967, pis. 2,4. 6; CP.-en, 1965, Figs. 7,8,10-12; Herrick and Vorhis,1963,Fig.10,14,16;Miller,1986;Huddlestunand others, in manuscript). Therefore, there is no stratigraphic evidence for the existence of the arch.

100

A second line of reasoning involves regional subsiding basin, to the east. It is the juxtaposition of the

strike. The structural strike of various Upper Gulf Coast Basin and the Gulf Trough that gives the

Cretaceousand Tertiaryhorizons and the outcrop pattern illusion of the presence of an arch in the area between.

of Tertiary strata in the vicinity of the postulated

In summary, I strongly urge that the use of the

Chattahoochee Arch in the Florida panhandle is approxi- names Chattahoochee Arch, Chattahoochee uplift, and

mately west-northwest-east-southeast to east-west Chattahoochee anticline be discontinued. No data have

(Applin and Applin, 1967, Pis. 2,4,6; Chen, 1965, Figs. 1, been presented by any author that supports the existence

8, 10-12; PennWell Publishing Co., 1982; Huddlestun, of the Chattahoochee Arch, and all of the published data

1984, Figs. 6-9; Huddlestun and others, in manuscript; relevant to the Chattahoochee Arch are incompatible

also compare with Applin and Applin, 1944; Herrick and with the presence of an arch, anticline, or uplift at the site

Vorhis, 1963; American Association of Petroleum Geolo- of the postulated structure.

gists, 1975). In contrast, the strikes of the various postu-

lated axes of the Chattahoochee Arch vary from approxi- Barwick Arch

matelynorth-southto southwest-northeast(see Patterson

and Herrick, 1971, Fig. 1). If there were a structural arch

The Barwick Arch was named by Sever (1966a, p.

in the vicinity of the postulated Chattahoochee Arch, the 7-8, Figs. 2-6) for a southwest-northeast trending struc-

resulting deflection in the regional strike of formations tural high on top of the Suwannee Limestone in Thomas

and stratigraphic horizons should be evident in local County, Georgia. He described the structure as follows:

occurrencesofnorth-southor southwest-northeaststrikes.

No such trends are evident, and no such strikes have been

Contours drawn on the top of the

reported.

Suwannee Limestone of Oligocene

Structural strikes of stratigraphic horizons or

age and the Tampa Limestone of early

formations in Alabama (Cooke, 1926, pl. 1; PennWell

Miocene age...show that these rocks in

Publishing Co., 1982), and Georgia (Herrick and Vorhis,

northwestern Thomas County are

1963;Chen,1965;Huddlestunandothers,inmanuscript),

downfolded along a northeast-plunging

also suggest that there is a smooth, general rotation of

structure called the Miegs basin... In

structural dips around the southeastern corner.of the

central Thomas County the rocks have

continent in eastern Alabama and western Georgia. The

been upfolded along a northeast

southeastern comer ofthe continentis thus characterized

trending arch named the Barwick Arch.

bya gradual swingofstructural contourson stratigraphic

These folds are separated by the

horizons from west-northwest-east-southeast in Ala-

Ochlockonee fault which has a

bama and western Florida (eastern Gulf Coastal Plain) to

displacement of about 200 feet in

southwest-northeast in Georgia (Atlantic Coastal Plain).

northern Thomas County... Rocks on

This gradual rotation of the structural contours is inter-

the southeast side of the fault are

rupted in the upper part of the geologic section (Middle

upthrown with the amount of

Eocene-Middle Miocene) by the presence of the Gulf

displacement increasing to the northeast.

Trough in the eastern panhandle of Florida and south-

western Georgia. Were it not for the presence of the Gulf However, Patterson and Herrick (1971, p. 13) concluded:

Trough, the structural contourson stratigraphichorizons

in the upper part of the section would probably trend

The elevations of the top of the Suwannee

east-west across the panhandle of Florida (compare with

that were determined at many well

the Oligocene'outcrop belt in American Association of

sites and outcrops do not differ

Petroleum Geologists, 1975).

greatly from those illustrated by Sever

A third line of reasoning results from the older

(1966a, Fig. 1: 1966b, Fig. 2). We therefore

formations occurring at relatively high elevations in the

agree with Sever to the extent that the top

Holmes-Washington-Jackson Counties area of Florida.

of the Suwannee is high in the vicinity

When considering only the structural attitudes of forma-

of his "Barwick Arch".., which is a short

tions in Florida and ignoring those in Alabama and

distance east of the proposed fault ....

Georgia, the structurally high occurrences of those for-

mations in Florida give the appearance of an "arch" or

The "high" in the top of the Suwannee

"uplift." The appearance of an arch in Florida is inferred

Limestone along the so-called Barwick

by the occurrence of the Gulf Coast Basin (or Gulf of

Arch of Sever (1966a, Fig. 1; 1966b, Fig. 2)

Mexico sedimentarybasin, orGulfgeosyncline ofMurray,

does not prove the existence of this

1961), a tectonically subsiding sedimentary basin to the

anticline, and it too should be

west, and the Gulf Trough which is not a tectonically

questioned. One of the reasons for

101

questioning this arch is that water wells in this vicinity do not penetrate through Oligocene rocks, and there is little information to prove or disprove the existence of such a feature. With the evidence now available, we cannot rule out the possibility that the apparent reversal of the regional dip from the arch into the Gulf Trough is an initial dip resulting from deposition on the east side of a strait or a submarine valley. The apparent dips in this vicinity also may have been modified significantly by carbonate solution, inasmuch as structure contour maps on the top of the Oligocene in areas south of the arch (Hendry and Sproul, 1966, Fig. 16; Yon, 1966, Fig,. 10) show a buried karst topography having high areas of the same magnitude as that illustrated by Sever for Barwick Arch.
So, the original basis for postulating the existence of the Barwick Arch was the supposed topographically high (and presumable structurally high) occurrence of Suwannee Limestone and Chattahoochee Formation ("Tampa Limestone") along a southwest-northeast trend that passes near the community of Barwick in Thomas County, Georgia (Sever, 1966a, Figs. 2 and 3). Based on cores in the same area, I have not been able to reproduce the structurally high upper contact of the Suwannee Limestone (Pl. 3) and, based on cores and well-cuttings, only a broad, low "undulation" is recognizable on top of the Suwannee Limestone south of the Gulf Trough in southwesternGeorgia (Huddlestun and others, in manuscript). In addition, structural contours on stratigraphic horizons older than the Middle Eocene show no indication of an arch in the postulated position of the Barwick Arch (see Herrick and Vorhis, 1963; Applin and Applin, 1967; Huddlestun and others, in manuscript). Because older reports based on deep but sparse control, and newer reports with more stratigraphic control than that of Sever (1966a) do not show any evidence for the existence of the Barwick Arch, it is concluded that the Barwick Arch of Sever (1966a) does not exist as a structural arch (a feature resulting from tectonic processes).
A low, broad undulation on the top of the Oligocene does occur parallel to and south of the Gulf Trough, roughly in the position of the Barwick Arch, and may have resulted from one of two causes. The high occurrence of the Suwannee Limestone (and adjacent formations) may result from the interruption of the normal regional dip to the southeast by the depression of stratigraphic horizons within the Gulf Trough (see Pl. 3). Therefore the Barwick Arch, or the low, broad undulation

south of the channel, is an artifact of the Gulf Trough much as is the Chattahoochee "arch" in western Florida.
Alternatively, this low, broad undulation could be the result of increased sedimentation rates on the southern flank of the Gulf Trough. The sea floor would stand bathymetrically high where there was greater organic production and, therefore, greater rates of sedimentation (much as a bioherm). In support of this model, it is in the vicinity of the community of Pavo (near Barwick) in eastern Thomas County that the relatively thick Bridgeboro Limestone grades laterally southeastward into the Ellaville Limestone and Suwannacoochee Dolostone (Pl. 3) both of which are restricted to and characteristic of the Florida Platform.
The results of current investigations support the conclusionofPattersonand Herrick(1971) that the Barwick Arch does not exist. I therefore also recommend that the name Barwick Arch be abandoned because, with increased and improved data and stratigraphic control, the presence of the arch as a structural (tectonic) feature has not been verified and its presence as a sedimentary constructional feature, if real, 'is trivial.
Faults
A number of faults have been proposed to account for lithostratigraphic and thickness anomalies in thevicinityoftheGulfTrough(seePattersonandHerrick, 1971). All of these proposed faults can be interpreted as involving Oligocene stratigraphy or sedimentation patterns. Consequently, they should be discussed in this report. Those postulated faults that can be construed to bound the Gulf Trough (or Chattahoochee Embayment) include two parallel, unnamed faults with downthrown southeastern sides (Callahan, 1964, p. 33); '1inears" or faults which bound the South Georgia Trough, or graben (Gulf Trough), of Tanner (1966, p. 84, 85, 87) (in part the Bainbridge-Chattahoochee-Blountstown fault as interpreted by Patterson and Herrick, 1971); the Cypress fault of Moore (1955, p. 26-29) which marks the western flank of the Chattahoochee Embayment in Jackson County, Florida; and the Ochlockonee fault of Sever (1966a, p. 78, 1966b) which bounds the southeastern flankoftheGulf Trough in Thomas County, Georgia. Concerning these faults, Patterson and Herrick (1971, p. 13) concluded:
...none of the reports in which faults outlined above were proposed, present adequate supporting evidence. Insofar as the authors of this article are aware, mo-st of these faults are hypothetical.
The above observation also holds for subsequent reports where the Gulf Trough is interpreted as being a fault-bounded structure (Cramer and Arden, 1980;

102

GelbaumandHowell, 1982;Miller, 1982, 1986). Similarly, no data hasbeen submitted that supports the existence of the BigSatillafaultofGelbaumand Howell (1982, p.149).
There is no evidence for fault displacement of the top of the Cretaceous in the vicinity of the Gulf Trough in Georgia (Huddlestun and others, in manuscript; also compare with Herrick and Vorhis, 1963; Applin and Applin, 1967) or in the vicinity of the Chattahoochee Embayment in Florida (see Chen, 1965, Fig. 8; Applin and Applin, 1967, Pl. 6C). Therefore, it is concluded in the present report that all of the above faults are hypothetical and have not been shown to exist.
PALEOGEOGRAPHIC ELEMENTS
Florida Bank
For a substantial period of the history of the Coastal Plain Province, the physiographic expression of the FloridaPlatform was that of a marine, shallow-water, carbonate bank analogous to the present Bahamas Banks (Fig. 45, 46). The surface of the platform did not become a shallow water bank until near the end of the Tayloran (Campanian) or beginning of the Navarroan (Maastrichtian) when the Lawson Formation, the first of the carbonate bank formations, was deposited on the deeper water Pfne Key Formation. Prior to the deposition of the Lawson Formation, the physiographic expression of the Florida Platform during the Late Jurassic, Early Cretaceous, and early Late Cretaceous was a peninsula, island, or archipelago of moderate to low topographic relief (Levy Hills of Banks, 1976a). This land area was surrounded by a shallow shelf upon which siliciclastic sediments were deposited in the north and upon which shallow water carbonates and evaporites were deposited in the south (see Applin and Applin, 1965, 1967; Babcock, 1969). The Florida Bank probably persisted as a physiographic feature from the latest Cretaceous into the Early Miocene. During the Miocene, siliciclastic shelf sediments, eroded from the rejuvenated Appalachian Mountain system, spread southward across the shelf from the Georgia area into the Florida area. Before the end of the Middle Miocene, siliciclastic sedimentation sutured the former Florida Bank onto the continental mainland as the Florida peninsula and filled the Gulf Trough and made the former bank continuous with the continental shelf.
The northern bank-edge of the Florida Bank is defined by the northernmost occurrence of Florida Bank carbonate formations. These include in ascending order: the Upper Cretaceous Lawson Formation, the Paleocene to possibly Lower Eocene? Cedar Keys Formation, the Upper Paleocene? to Lower Eocene? Oldsmar Formation, the Middle Eocene Avon Park Formation (including the Lake City formation of Applin and Applin, 1944), the Oligocene Suwannacoochee Dolostone, and the Oligo-

cene Suwannee Limestone. The northern bank-edge occurred on the southern flank of the Suwannee Channel during the latest Cretaceous through Middle Eocene. The Florida Bank environment prevailed briefly north of the trough during deposition of the late Vicksburgian Suwannee Limestone (Fig. 46). Although there were bathymetric highs''and lows on the floor of the Suwannee Strait and former Florida Bank during the Late Eocene, the Florida Bank environment ceased to exist at that time in onshore Georgia and Florida. Despite the Gulf Trough having been initiated during the Middle Eocene, the northern bank-edge of the Florida Bank remained on the southern flank of the Suwannee Channel during that time.
The site of the Suwannee Channel remained a site of relatively deep water during the Middle Eocene and the channel does not appear to have been filled in until the end of the Middle Eocene. Although the Suwannee Strait continued to exist through the Late Eocene, carbonate shelf conditions prevailed during that time from the nearshore, inner neritic shelf and coastal area (where they interfingered with the coastal, siliciclastic Barnwell Group), across the Florida Platform almost to the shelf edge. This great expanse of shelf carbonates (Ocala Limestone) was bisected by the Gulf Trough in which deep-water limestones were deposited (Fig. 47).
During the Late Eocene, then, the Florida Bank does not appear to have existed as a discrete paleogeographic province on the present peninsula of Florida. It is probable that bank-type conditions continued to prevail on the Florida Platform under the present western peninsular Florida continental shelf of the Gulf of Mexico because the younger, Oligocene Suwannee Limestone containsa few taxa commonto relictFlorida Bank (Tethyan or Caribbean) foraminiferal fauna (with special reference to Dictyoconus cookei, D. floridana, Valvulimmina spp., Valvulina spp., and Discorinopsis spp.) that is characteristic of Middle Eocene and older sediments of the Florida Bank. This Tethyan (Caribbean) fauna must have existed in refugia somewhere nearby during the Late Eocene, as discussed earlier, because there seems to be no record of it in the world after the Middle Eocene (also see Cole and Applin, 1964). Therefore, as such the Suwannee Strait must have continued to exist, but the site of the strait, in the strict sense, would have been farther west than the earlier strait.
At the end of the Eocene and during the Early Oligocene, there were a series of sea level drops and low stands punctuated by progressively lower high stands (Pl. 1). During the early Vicksburgian, water depths on the Florida Platfo:r:m remained sufficiently great so that carbonate shelf conditions continued to prevail across most of the shelf as during the Late Eocene. However, with the abrupt fall in sea level (that resulted in the deposition of the Suwannacoochee Dolostone), Florida

103

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t

Gulf of Mexico
0 10 20 30 40 50 miles
A E3 E3

Atlantic Ocean

Figure46.

Early Oligocene paleogeographic elements of Georgia and northern Florida. 104

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BANK?

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0 10 20 30 40 50 miles
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Figure47.

Late Eocene paleogeographic reconstruction of the Coastal Plain area of Georgia and northern Florida.

105

Bank conditions became reestablished across the entire continental shelf of Georgia (excluding the Gulf Trough). Additional distinctions between the Florida Bank of the Oligocene and the earlier Cretaceous-through-MiddleEocene Florida Bank exists. Whereas the earlierbank was topographicallydiscontinuousandfaunallyisolatedfrom the continental shelf region north of the Suwannee Channel, during the Oligocene the Florida Bank bathymetrically and faunally was continuous with the continental shelf around the eastern end of theGulf Trough in eastern Georgia. This permitted some degree of faunal interchange between the continental shelf region and the Florida Bank. The most widespread Oligocene bank limestone formation (Suwannee Limestone) is a modified bank formation, being environmentally, lithologically, and faunally intermediate between the earlier Cretaceous-and-Early-Tertiarycarbonatebank formations and the continental shelf carbonate units (Ocala Limestone and Ellaville Limestone). This indicates that there was only a partial return to the earlier carbonate bank environment during the Oligocene.
The Florida Bank as a shallow water carbonate bank probably ceased to exist in Georgia after Vicksburgian time but a bank type of environment probably persisted somewhere else on the continental shelf of Florida throughout the Oligocene. Although Upper Oligocene (Chickasawhayan) deposits are not present in Georgia, even within the Gulf Trough. Their presence has not been conclusivelydemonstrated in peninsular Florida. The vestiges of a Florida Bank (Tethyan) foraminiferal fauna in the Early Miocene, Aquitanian Chattahoochee Formation in Florida and Georgia (e.g., Discorinopsis sp.) requires the persistence of the Oligocene fauna in refugia during the later Oligocene. However, during the Late Oligocene, the former bank was continuous with the mainland and the bank had been grafted onto the continental mainland as a peninsula (Fig. 48).
Based on the occurrence of Arikareean land mammals in peninsular Florida (Tedford and Hunter, 1984), it is clear that terrestrial conditions had certainly become established on the Florida Platform by the Early Miocene (Aquitanian), and the former bank may have become physiographically a part of the continental mainland at least during low sea level stands of the Oligocene and Miocene. It is possible that parts of the Florida Bank continued to exist during the earliest Miocene (Aquitanian). Islands analogous to the Bahamas Islands of today would occur on the topographically highest parts of the bank and carbonates were deposited in the topographic (or bathymetric) lows (Tampa Limestone Member of the Arcadia Formation (Scott, 1988) and associated shallow water carbonates). However, the Florida Bank as such certainly ceased to exist in the late Early Miocene (Burdigalian) 'Yhen siliciclastics

(Hawthorne Group) from the Piedmont finally inundated and buried the shallow-water, carbonate sediments of the Florida Bank.
Suwannee Strait
The name Suwannee Strait has often been used synonymously with Apalachicola Embayment, Suwannee Channel, and Gulf Trough. However, as defined by Huddlestun and others (in manuscript) and as applied in this report, the Apalachicola Embayment, Chattahoochee Embayment, Gulf Trough, Tallahassee Embayment, and Suwannee Channel are sediment filled channel structures and they are defined on their channel morphology and their sediment fill. The term "strait," however, is a geographic descriptive term that is defined as a narrow marine passage connecting two larger bodies of water. The word "strait," therefore, is not a morphological or sedimentary descriptive term and can not be applied to the above sedimentary constructional features (channel structures).
In the introductionofthename "SuwanneeStrait," Dall (1892, p. 111, 120-122) described the Suwannee Strait as,"a passagebetweenFlorida and the mainland" (p.121) and noted that the strait was now completely sediment filled. Dall (1892) was unaware of the existence of the Suwannee Channel and Gulf Trough and gave no evidence or clear idea of the existence of the channel system as presently understood. Therefore, in this report the name Suwannee Strait is used in the paleogeographic sense of Dall (1892) as that constricted marine seaway ~onnecting the Gulf of Mexico with the Atlantic Ocean across the eastern panhandle of Florida and southern Georgia (Figs. 49, 50). Typically a strait occurs between two shoals or land masses. The later may have been the caseduringearlyEaglefordian to Austinian (Cenomanian to Santonian), during the Miocene history of the strait, and during the Early Pleistocene high stands of the sea (that produced the high marine terraces in Georgia) between the continental shoreline and the Brooksville Ridge in Florida. However, during much of the history of the Suwannee Strait, the strait was flanked on the north by the continental mainland and on the south by the shallow water expanse of the Florida Bank.
During the history of the Suwannee Strait, the northern margin of the strait remained in the coastal area of the continental mainland of North America whereas the southern margin shifted through time (Fig. 46). During the early part of the Late Cretaceous (Eaglefordia:n to Austinian), the southern margin of the strait was an island or archipelago on the Peninsular Arch in northeastern Florida (see Applin and Applin, 1967; Babcock, 1969) and has been referred to as the Levy Ranges by Banks (1976a). Later in the Cretaceous (upper Tayloran or Navarroan [upper Campanian or Maastrichtian])

106

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0 10 20 30 40 50 miles

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Figure48.

Latest Oligocene paleogeographic reconstruction of the Coastal Plain of Georgia and northern Florida.

107

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GULF OF MEX~- -

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Suggested Bathymetric Contours Ocean Currents

Figure49.

Proposed paleogeographyand paleoceanographiccurrent distributionsofthe Florida andSuwannee Strait Region during the Midwayan highstand of the sea.

108

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Figure 50.

Proposed paleogeography and paleoceanographic current distribution of the Florida and Suwannee Strait region during the Sabinian high stands of the sea.

109

through Middle Eocene, the southern margin of the Suwannee Strait was the southern margin of the Suwannee Channel and northern bank-edge of the Florida Bank.
During the Late Eocene, most of the Suwannee Strait area and much of the former Florida Bank was combined to form an areally extensive carbonate shelf bisected by the deeper-water Gulf Trough (Figs. 47, 51). However, the site of the former Florida Bank still remained a site ofshallower waterdepositionin peninsular Florida (Carter, 1990). In addition, the proposed refugia of the Tethyan (Caribbean) foraminiferal fauna suggests that a small portion of the Florida Bank continued to exist on the continental shelf off the present coast of the northwestern peninsula of Florida. Therefore, a strait probably still existed in the region during the Late Eocene.
When the Florida Bank became reestablished in peninsular Florida during the late Vicksburgian, due to relative lowering of sea level, the Suwannee Strait as it had existed earlier was not reestablished. In the central Coastal Plain of Georgia, the Florida Bank Suwannee Limestone extended approximately 40 miles (64 km) north of the Gulf Trough and probably extended into the coastal marine area during that time. Therefore, most of the continental shelf that had been the Suwannee Strait briefly became Florida Bank (Fig. 45). During that period of time (deposition of Suwannee Limestone) and later during the Oligocene, the only feature that could be equated with the Suwannee Strait would have been specifically the Gulf Trough. In other words, during these periods of time, the Suwannee Strait would have been confined to the Gulf Trough.
Duringlow sealevel stands intheLate Oligocene to the early part of the Middle Miocene, the Suwannee Strait region was a partof the continental mainland to the north and land areas on the former Florida Bank to the south. Thus, a paleo-Florida Peninsula came into existence (Fig. 48). During the Early and early Middle .Miocene high stands of the sea, the Suwannee Strait continued to exist as a shallow water seaway in the unfilled Gulf Trough between the continental mainland to the north and a landmass, island, or archipelago in peninsular Florida to the south. After prograding fluvial deposits (Altamaha Formation) filled in and buried the Gulf Trough during the early Middle Miocene, the Suwannee Strait no longer existed, except briefly during the Early Pleistocene.
Atlantic Continental Shelf
This is a vaguely defined belt that roughly parallels the trend of the continental shelf in southern South Carolina and northern coastal Georgia. Oligocene sediments of varying lithologies and depositional environ-

ments are present in this area and, locally or regionally, Oligocene sediments are also absent (Fig. 32, 35, 46). Deeper water sediments are present onshore in southern South Carolina and on the continental shelf of Georgia (Cooper Formation). Shallow-water, sandy sediments are present in the northern coastal area of Georgia but correlative sediments are absent in the Port Royal Sound area of South Carolina and in southeastern Georgia and eastern Florida south of Glynn County, Georgia. The stratigraphic variability of the Atlantic coastal and continental shelf area Q.uring the Oligocene suggests an environmentally distinct region from that of the continental shelf of the eastern Gulf Coastal Plain, Florida Bank, or Suwannee Strait.
SUWANNEE CURRENT
The Suwannee Current was identified by Huddlestun and others (in manuscript) as a gradient current that was generated by the hydrostatic head between the Gulf of Mexico and the Atlantic ocean. During its entire existence, the Suwannee Current served along with the Florida Current as the major currents passing from the Gulf of Mexico into the Atlantic Ocean (Figs. 4951). The Suwannee and Florida Currents can be viewed as sibling currents. The Florida Current appears to have come into existencefirst, probablyduring the Cenomanian, and is the surviving current. The Suwannee Current seems to have come into existence somewhatlater during the Late Cretaceous and is a northward continuation of the paleo-Caribbean Currentin the easternGulfofMexico. After passing through the Yucatan Strait, the paleo-Caribbean Current separated into two currents, an eastward flowing current (paleo-Florida Current) that passed through the Straits of Florida into the Atlantic Ocean, and a northward flowing current (Suwannee Current) that flowed into the Atlantic Ocean through the Suwannee Strait. The northern outlet of the Gulf of Mexico, the Suwannee Strait, is thought to be the natural outlet from the Gulf of Mexico for the Caribbean Current because of both the inertia of the moving water mass and the Coriolis effect. However, the northern outlet was more vulnerable to tectonism on the margin of the North American continent, to eustatic falls in sea level, and to sedimentation which ultimately filled the outlet. It was the combinationofthe last two factors that terminated theSuwannee Current during the Oligocene, leaving the Florida CurrentastheonlycurrentexitingtheGulfofMexicointothe Atlantic Ocean.
The Suwannee Current is envisioned as having occupied that water mass within the upper part of the water column of the marine channels (Suwannee Channel and Gulf Trough) during the Oligocene high stands of the sea (Huddlestun and others, in manuscript). During these high stands, it is thought that the current was not entirely

110

N
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---
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Suggested Bathymetric Contours Ocean Currents

Figure 51.

Proposed paleogeography and current distribution of the Florida and Suwannee strait region d~ring the late Jacksonian.

111

confined to its channel but that the margins of the current also extended some distance beyond the channel proper and may have had some latitude for lateral movement (Fig. 52). During the low stands of the sea, however, the Suwannee Current is envisioned as having been lowered into the channel, confined to the channel or locked in place, thus frequently resulting in nondeposition within the channel or, during more drastic sea level low stands, scouring the floor of the channel (Fig. 51).
OLIGOCENE FAUNAL PROVINCES
Three faunal provinces (or subprovinces) were present in the southeastern Coastal Plain during the Oligocene (Fig. 53). Although the Oligocene faunas characteristic of each province have not yet been so identified in the literature, they are recognized in this report and briefly described. For discussion purposes, the three faunal provinces are referred to as the Gulf of Mexico faunal province, the Atlantic faunal province, and the Florida faunal province. The Gulf of Mexico and the Atlantic faunal provinces were physically connected throughout the Late Cretaceous and Early Tertiary, but were probably faunally distinct because of currents, differing water-masses, and differing substrate on the continental shelf. The Gulf of Mexico and the Atlantic faunal provinces were probably subdivisions of a larger western North Atlantic continental shelffaunal province. The Florida faunal province, on the other hand, was isolated from the other two provinces and appears to have been a subdivision of the Caribbean (or Tethyan) faunal province.
The most thoroughly described of these faunas is that of the continental shelf of the eastern Gulf of Mexico (Gulf of Mexico faunal province) or Gulf Coastal Plain (For Oligocene faunas, see Cushman, 1922a, l922b, 1923, 1929, 1935; Cushman and McGlamery, 1938, 1939, 1942; Cushman and Todd, 1946, 1948; Cole and Ponton, 1930; Bandy, 1949; Todd, 1952; Poag, 1966; Hazel and others, 1980; Mansfield,1938,1940; Dockery,1982; MacNeiland Dockery, 1984; Cooke, 1942, 1959). The Oligocene foraminiferal fauna of the Gulf of Mexico faunal province in Georgia includes the faunas of the Gulf Trough (and Chattahoochee Embayment)(Bridgeboro Limestone and Ochlockonee Formation) and the Oligocene continental shelf region to the north and west of the Gulf Trough (Marianna and Glendon Limestones).
The Oligocene fauna of the Florida faunal province has not been as well documented as that of the easternGulfCoastalPlain(Cole,1941; ApplinandApplin, 1944; Horowitz, 1979; Mansfield, 1937; Hunter, 1972; and Cooke,1942, 1959) and, therefore, ithas notbeen seen to be faunally distinct. Earlier investigations on the older faunas of the Florida Bank (Applin and Applin, 1944; ApplinandJordan,1945; Cole and Applin, 1964,Palmer,

1953) indicated that the Middle Eocene Florida Platform fauna wasdramatically different from that of the contemporaneous faunas,.of the continental shelf region in Alabama but was strongly affiliated with th~ Caribbean (Tethyan) fauna. Palmer (1953) observed that the Avon Park and Inglis mollusks were closely related to the Tethyan faunal province of the Caribbean region and of the eastern hemisphere but unrelated to those of the continental shelf of North America. Evidently the deeper water conditions on the Florida Platform during the Late Eocene terminated most of the Tethyan faunal elements of the Florida faunal province. However, the marine environment in which the Tethyan fauna flourished was partiallyreestablished during theOligocene; and, briefly, the remaining faunal elements that had survived the Late Eocene submergence again flourished on the Florida Bank. An additional factor also subdued the faunal differences between the Oligocene continental shelf and Florida Bank. The Florida Bank was continuous with the Atlantic continental shelf in eastern Georgia; and, in the middleSavannahRiverarea, the Florida Bankfauna is the only foraminiferal fauna present (excluding the endemic foraminiferal fauna of the Lazaretto Creek Formation in Chatham County).
The Gulf qfMexico foraminiferal fauna is characterized by Pararotalia mexicana. This species is especially abundant in the Chickasawhayan deposits of Mississippi and Alabama. However, it is also present, but rare, in the Vicksburgian Mint Spring and Byram Formations in the eastern Gulf Coastal Plain. In Georgia, P. mexicana occurs throughout the Oligocene section. Pararotalia mexicana also occurs south of the Gulf Trough in Georgia, but it is less common there, and very rare in Florida (compare with Herrick and Vorhis, 1963, Fig. 5). Dictyoconus cookei, on the otherhand, isespeciallycharacteristic ofthe Florida faunal province during the Oligocene. It is also found within and on the northern flanks of the Gulf Trough in the central Georgia Coastal Plain, and in the Savannah River region northeast of the trend of the Gulf Trough. Elsewhere it is absent in Oligocene continental shelf deposits.
Among the mollusks, the Pecten perplanus stock, Chlamys anatipes and C. duncanensis are characteristic of Gulf of Mexico faunal province. Cardium suwanneense, Cerithium hernandoensis, C. hernandoensis blackwaterensis and Orthaulax hernandoensiss are characteristic of the Florida faunal province. Curiously, the Oligocene echinoids do not appear to show any substantial tendencies toward province preference (Carter, 1987).
The Atlantic faunal province is less well defined than the other two because of lack of study. The characteristic Atlantic Oligocene foraminiferal suites occur only in the shallow-water Lazaretto Creek Formation in the present coastal area of Georgia, and in the deeper water Cooper Formation in South Carolina and the continental

112

NW

SE

Sea Level High Stand

Suwannee Current

Gulf Trough

NW

SE

Sea Level Low Stand

Suwannee Current

Gulf Trough

Figure 52.

Hypothetical cross-section of the Suwannee Current in the Gulf Trough during the Oligocene high stands and low stands of the sea.

113

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Gulf of Mexico

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Figure 53.

Distribution of Oligocene faunas in the Coastal Plain of Georgia and northern Florida during the deposition of the Suwannee Limestone.
114

shelf of Georgia. The foraminiferal fauna of the Cooper is relatively deep water (probably outer neritic), but it is distinct from that of the broadly contemporaneous deepwater assemblages in the Ochlockonee Formation in the Gulf Trough in Georgia, and in the Marianna Limestone and Red Bluff Oay in south-western Alabama.
EOCENE I OLIGOCENE BOUNDARY
Two events described here are associated with the Eocene/Oligocene boundary in the southeastern United State and it is not clear which of these two events represents the cosmopolitan Eocene/Oligocene boundary. The first event is a change in the planktonic and benthic foraminiferal fauna that can be traced from Mississippi eastward to Georgia. In terms of planktonic foraminiferal zonation, it marks the zonal boundary between the Late Eocene Globorotalia cerroazulensis Zone (G. cerroazulensis cocoaensis) and the Early Oligocene Cassigerinella chipolensis- Pseudohastigerina micra Zone of Stainforth and others (1975). This boundary is interpreted as representing the standard Eocene/Oligocene boundary in condensed sections. There may also be an associated macrofossil change associated with this event but I have yet to locate a section in which the faunal change occurs with certainty in outcrop or in cores. The only areas that I know of that may contain dep&ition across this stratigraphic interval is in eastern Mississippi, and the tongue of Shubuta Clay in southwestern Alabama. In Alabama, whatever change in the macro- and microbenthos that may have occurred across that interval would be more deeply influenced by the change in the environment from carbonate shelf bottom to clay mud bottom. Elsewhere, there is no apparent lithologic change across this boundary where I have observed the overlying section.
The second event is a stratigraphic and benthic foraminiferal boundary. The stratigraphic boundary in question is the conventional top of the Eocene lithostratigraphic units in the southeast and, therefore, is arbitrarily defined as the Eocene-Oligocene boundary in this report. In eastern Mississippi this boundary represents the Shubuta Oay/Red Bluff Oay formation boundary; in eastern Alabama and Jackson County, Florida, it represents the Ocala Limestone/Bumpnose Limestone contact. These formation contacts represent the conventional boundary between the Jacksonian Stage and the Vicksburgian Stage. They also represent the conventional change between the relatively deep water, late Jacksonian foraminiferal suites in eastern Mississippi and western Alabama, and the progressively shallower water Vicksburgian foraminiferal suites of the same area. The second event is thought to represent the eustatic low stand event (TA4.4) of Haq and others (1987). However, it should be pointed out that the first event could also

have resulted in a shallowing from the typical Shubuta high-stand of the sea. The fauna is compatible with the interpretation that there was a lowering of sea level with the first event in that there appears to be lower faunal diversity in the Shubuta Clay and Ocmulgee Formation above the event. However, it is not clear whether the sea level fall that appears to have initiated the first event continued into the second event, or whether there were two very closely spaced falls in sea level, the second being the greater and correlated with TA4.4. Whichever the case, the two events described here that are associated with the terminal Eocene event in the southeast may appear as one event in condensed sections.
It is stressed that there are no clear, regional lithostratigraphic changes associated with the lower boundary. At the Red Bluff type locality at Hiwannee, Mississippi, the underlying Shubuta Clay is of characterisitic Shubuta lithology although its planktonic foraminiferal composition is that of the Cassigerinella chipolensis-Pseudohastigerina micra Zone. A similar situation prevails in the central Georgia Coastal Plain where all of the Ocmulgee Formation in the near vicinity of Hawkinsville, Pulaski County, Georgia, is correlated with the Shubuta sectiop at Hiwannee, Mississippi. That is, all of the Ocmulgee Formation exposed at and in the subsurface near Hawkinsville represents Ocmulgee Formation of the Cassigerinella chipolensis-Pseudohastigerina micra Zone. Virtually identical Ocmulgee Formation is exposed northwest of Hawkinsville (Stop 5 of Huddlestun and others, 1974) that contains a typical benthic and planktonic foraminiferal suite of the Globorotalia cerroazulensis Zone. In the near vicinity of Hawkinsville, however, no OcmulgeeFormationhasyet beenidentified that contains a G. cerroazulensis cocoaensis Zone planktonic foraminiferal suite.
Eastward from eastern Mississippi throughwestern Alabama, thehiatus betweenthe top of theJacksonian and the overlying Vicksburgian contains progressively more missingsection. TheuppersectionofShubutaCiay at St. Stephens Quarry and Little Stave Creek appears to contain the boundary "zone" of the G. cerroazulensis Zone and Cassigerinella chipolensis-Pseudohastigerina micraZone; but this zone as well as the Shubuta Oay thins progressively eastward. In the vicinity of Claiborne Bluff on the Alabama River, the Vicksburgian directly overlies Late Eocene carbonate~ that are lithologically transitional between the Shubuta Oay and the Ocala Limestone and which contain a planktonic foraminiferal suite of the C. cerroazulensis cocoaensis Zone. This stratigraphic sequence also prevails along the Conecuh and Sepulga Rivers in Covington and Conecuh Counties, Alabama (Huddlestun and Toulmin, 1965; Huddlestun, 1965), and inJackson County, Florida, where the lowerVicksburgian Bumpnose Limestone disconformably overlies Ocala Limestone containing a G. cerroazulensis cocoaensis Zone

115

planktonic foraminiferal fauna. The stratigraphy is more complex in the
Hawkinsville, Georgia, area, where the occurrence of the C. chipolensis-P. micra Zone of the Ocmulgee Formation is the only known occurrence of that zone within the Ocmulgee Formation. All other known planktonic foraminiferal suites from the Ocmulgee Formation are compatible with the G. cerroazulensis cocoaensis Zone and not with the C. chipolensis-P. micra Zone.
In summary, two events are recognized to be related to the Eocene\Oligocene boundary in the moderately extended (thickened) sections in the southeastern United States. The first and older appears to be largely a biostratigraphic event that contains the planktonic foraminiferal zone boundary between the G. cerroazulensis cocoaensis Zone and the C. chipolensis-P. micra Zone. Some benthic foraminiferal changes are also noted as occurring with this event, and other faunal changes may also to occur with it.
Planktonic foraminifera that do occur above this first biostratigraphic event include the following:
Globorotalia cerroazulensis cocoaensis Hantkenina alabamensis Cribrohantkenina inflata
Common benthic foraminifera that are not known to occur above this biostratigraphic event include the following:
Bulimina jacksonensis Uvigerina cocoaensis (in outcrop)
Bulimina sculptilis is a commonbenthic foraminifer that consistently occurs above this event but is not known to occur below it.
The second, younger event is a lithostratigraphic boundary, a stage boundary, and a biostratigraphic (benthic foraminiferal) boundary. Commonbenthic foraminifera that are not known to occur above the second biostratigraphic event include the following:
Planulina cooperensis Uvigerina jacksonensis Marginulina cocoaensis
Common benthic foraminifera that are not known to occur below the second biostratigraphic event include the following:
Lenticulina vicksburgensis Uvigerina vicksburgensis Planulina vicksburgensis

Bolivina caelata Cibicides cookei
It is not the function ofthis report to fully address the problem of the Eocene\Oligocene boundary in the southeastern United States. Therefore, the conventional Eocene\Oligocene boundary of the region that occurs at the Shubuta/Red Bluffcontact is that which is arbitrarily adopted here (Pl.l).
CORRELATION OF OLIGOCENE STRATIGRAPHIC UNITS,
SEQUENCE STRATIGRAPHY, AND PALEOGEOGRAPHY ACROSS
GEORGIA AND NORTHERN FLORIDA
Introduction
Near the end of the Eocene, the shoreline of Georgia lay directly on crystalline rocks of the Piedmont north of the present Fall line. Both because the lithology of the Upper Eocene deposits along the Fall line become progressively more marine in character westward in Georgia, and due to the presence of outliers of Barnwell Group on the Piedmont near Sparta in Hancock County and at the Fall line at Rich Hill in Crawford County, it is suggested that the shoreline at the end of the Eocene may have trended obliquely to the present Fall line, being oriented more east-west. As a result, in western Georgia theshorelineattheendoftheEocenernayhavebeenasfar north as the vicinity ofPine Mountainin Meriwether and Harris Counties (Fig. 51).
Because the uppermost Eocene deposits (Ocala Limestone) contain a rich and diverse biota, it is inferred from the present study that they were deposited within the photic zone in water depths probably not much greater than 200 feet (61 m) and possibly less (also see Cheetham, 1963, p. 31-33). Haq and others (1987) have estimated a eustatic sea level drop of about 165 feet (50 m) at the end of the Eocene. A sea level drop of roughly 165 feet (50 m) would have caused a significant seaward retreat of the shoreline and left much of the continental shelf covered by very shallow water. The Suwannee Current during this low-stand would have been entirely confined to the Gulf Trough.
This scenario is supported by the common occurrence of dolomitization near the top of the Ocala Limestone south of the Gulf Trough and the less common occurrence of intraclastic or brecciated dolostone at the top of the Ocala Limestone in cores from southernmost Georgia. Within the Gulf Trough, either dolomitization occurs at the top of the Eocene or there is a sharp disconformity at the topo.f the Eocenebelowa basal Ochlockonee phosphatic zone. The disconformity at the top of the Eocene section within the Gulf Trough is consistent with

116

the Suwannee Current having been lowered into and and in Georgia. However, no Oligocene sediments have

confined to the trough at the end of the Eocene, resulting yet been identified in the near vicinity of the Fall line in

in a lowered baselevel and and nondeposition or scour Georgia. The known updip limits of Oligocene deposits

within the trough. Dolomitization at the Eocene-Oligo- in Georgia, most of which consists of residuum in out-

cene boundary within the Gulf Trough may be explained crop, occur between 20 and 30 miles (32 to 48 km) south

by the influx of chemically abnormal sea-water flowing of the Fall line and along a line from the Screven-Burke

into the trough as density currents from the very shallow Counties line on Brier Creek in the east, through northern

water expanse of continental shelf adjacent to the Gulf Emanual County, northern Laurens County, to southern

Trough.

Twiggs and Houston Counties in the west (Fig. 10). This

The position of the shoreline and the paleogeog- Oligocene residuum is overlapped by fluvial deposits of

raphy of the Georgia Coastal Plain during the terminal the earliest Miocene, Aquitanian, Altamaha Formation

Eocene,low stand of the sea can only be approximated in (Huddlestun, 1988) from western Screven County in the

this report (Fig. 54). There is no record of any coastal east to the vicinity of the Oconee River in the west. In that

marine deposits known to be associated with this eustatic area, the updip limits of the Oligocene occur in the

low stand of the sea, and the apparent absence of the subsurface. Farther updip, the Altamaha Formation di-

Bumpnose-Red Bluff sequence in Georgia combines to rectly overlies the Upper Eocene, Barnwell Group in

eliminate any possibility at this time ofprecisely identify- outcrop. In eastern Georgia, the Oligocene outcrop belt

ing either of these geographic features.

occurs only in northern and eastern Screven County

The beginning of the Oligocene Epoch as recog- (Figs. 10 and 32).

nized in this report commenced with the rise in sea level

Incentral Georgia from northernLaurens County

after the abrupt eustatic fall in the sea that is interpreted to Houstonand Pulaski County (also see Pickering, 1970),

to be TA4.4 of Haq and others (1987). Baum and Vail however, either the Altamaha Formation or Hawthorne

(1988, Mancini and Tew, and Tew and Mancini (1992) Group deposits directly overlie deeply weathered Oligo-

have argued that the Eocene/Oligocene boundary in the cene deposits or residuum. North of this there is no

eastern Gulf coastal Plain is a condensed section pro- information because both the Altamaha and Oligocene

duced by a high stand of the sea rather than an erosional have been removed by late Tertiary or Quaternary ero-

or nondepositional disconformity. They place the Lower sion.

Oligocene Forest Hill Formation and Red Bluff Clay

In western Georgia, the northern limit of Oligo-

within their Upper Eocene TE3 sequence. Dockery (1990) cene residuum extends southwestward through Sumter

' and Coleman and Galloway (1990) have presented evi- to northern Randolph Counties (Fig. 10). Residuum that

dence that the Eocene/Oligocene boundary does indeed may include Oligocene material occurs as far north in

represent an unconformity. Myobservationsare compat- western Georgia as the vicinity of Preston in Webster

ible with those of Dockery (1990) and Coleman and County and Buena Vista in Marion County (Georgia

Galloway, 1990).

Geological Survey, 1976).

After this terminal Eocene low stand of the sea,

Except for the coastal area during the Oligocene,

there was a succession of four progressively lower high most of the Suwannee Strait region remained within the

stands of the sea during the Vicksburgian. These high carbonate deposition province. In contrast to the preced-

stands were punctuated by progressively more severe ing Late Eocene, h.owever, the Gulf Trough during the

but brief low stands of the sea that were unrecorded by Oligocene exerted a profound influence on the carbonate

Haq and others (1987) (Pl. 1). With the low stand ofthe sea sediment distribution patterns in the Suwannee Strait

at the close of the Vicksburgian Stage (probably TA4.5 of region. The Vicksburg Group and its offshore strati-

Haq and others, 1987), itislikely that even the floor of the graphic equivalent, the Florala Limestone Member of the

Gulf Trough was subaerially exposed. It is interpreted Bridgeboro Limestone, are restricted to the continental

here that the progressively falling sea level, with progres- shelf region north and west of the Gulf Trough. A

sively more severe low stands of the sea during the different suite of formations, typically exposed along the

Oligocene, culminated in the reduction and final termina- Suwannee River in Florida, is restricted to the shallow

tion of the Suwannee Current and initial filling of the Gulf shelf region south of the trough. The Gulf Trough, on the

Trough. Although there is evidence that the Suwannee other hand, contains a unique suite of formations that

Current was severely diminished as a gravity current at initially were ofrelatively deep water origin. However, as

the end of the Eocene, there also is evidence that the the Gulf Trough filled with sediment and sea level con-

Suwannee Current, in a progressively diminishing state, currently dropped late in the Vicksburgian, the younger

continued to occupy the Gulf Trough during the high formations were deposited in progressively shallower

standsofthe sea through the duration oftheVicksburgian. water. A rhodolithic limestone, the Bridgeboro Lime-

Oligocene deposits appear to be slightly regres- stone, occurs on both flanks of the Gulf Trough in south-

sive in relation to the Upper Eocene deposits in Alabama western Georgia, but is more prominently developed on

117

N
t
- 32~

Atlantic Ocean

n.
Gulf of Mexico

0 10 20 30 40 50 miles

H

H

H

'l_ ""-

VOLUSIA

'-../""'-' r-
\j

Figure 54.

Paleogeographic reconstruction of Georgia and northern Florida during the terminal Eocene low stand of the sea.

118

the north side of the trough.

Depositional history

Because all ofthe nearshore Oligocene sediments

consist of limestones, clayey residuum with silicified limestone, or fine-grained siliciclastics (clay and finegrained sand), it is suggested that the Piedmont rivers during the Oligocene were near geomorphic base-level and were not undergoingincision into fresh countryrock. The lithology of the updip Oligocene deposits is compatible with only mild erosion of saprolite (i.e., minor influx of siliciclastic sediments). According to this model, then, at the beginning of the Oligocene much of the Georgia

In this report, the Oligocene Series is divided into five depositional sequences or phases that were deposited during eustatic high stands of the sea (Pl. 1). These high stand deposits are separated from each other either by disconformities or by dolostones postulated to have been deposited during low sea level events. The depositional sequences (or stratigraphic intervals) include from oldest to youngest:

Coastal Plain was part of the continental shelf (Fig. 54), and either there was no coastal plain at that time or it

Disconformity or paraconformityon top ofOcala

consisted at the most of a narrow, marshy, swampy plain between the topographically subdued Piedmont to the 1) Bumpnose-Red Bluff-Forest Hill depositional sequence

north and the open ocean to the south. As with the underlying Upper Eocene, there are

Post-Bumpnose-Red Bluff hiatus-Paraconformity

no discernable systematic lithologic differences between

the Oligocene formations on the site of the Middle Eocene 2) Ellaville-Marianna-MintSpring-Glendon depositional

and older Florida Bank and the same formations on the

sequence

site of the former Suwannee Channel. Therefore there

were only minor bathymetric or other environmental

Disconformity or gradation- Suwannacoochee

differences between the sites of the former Suwannee

low stand of the sea

Channel and the Florida Bank region to the south.

The diminishing of the Suwannee Current after 3) Suwannee-Byram depositional sequence

the Eocene is indicated from two other lines of reasoning.

(1) During the Middle and Late Eocene, deposits within

Disconformity or gradation- Wolf Pit low stand

the Gulf Trough were thin compared with correlative

of the sea

deposits outside of the trough. In contrast, the Oligocene

is very thick within the Gulf Trough compared with the 4) Okapilco-Bucatunna depositional sequence

thickness of the Oligocene outside of the trough. (2) The

deposits within the Gulf Trough consist of thick accumu-

Disconformity- post-Vicksburgian low stand of

lations of finely granular, foraminiferal limestone and

the sea

minor dolostone. In the vicinity of the Florida state line,

the Oligocene fill in the trough is approximately 1000 feet 5) Chickasawhay depositional sequence

(305m) but thins rapidly northeastward in the trough (Pl.

2). From Colquitt County to Jeff Davis County the Oligo-

Disconformity-post-Chickasawhaylowstand(s)

cene channel fill a:verages about 400 to 500 feet (122 to 152

of the sea

m) but in Toombs County it has thinned to less than 400

feet (122m). The main part of the Oligocene channel-fill,

The following discussion will be based on

the Ochlockonee Formation, ranges from near 300 feet (91 correlationof all other formations with these standard,

m) in Coffee County, thins to a little more than 250 feet (76 provincial Vicksburgian and Chickasawhayan forma-

m) in the vicinity of the Peninsular Arch in Berrien tions. It is noted here, however, that the interpretations

County, thickens to almost 400 feet (122 m) in Colquitt by Dockery (1982), MacNeil and Dockery (1984), and

County, and then thickens to almost 900 feet (274m) near Dockery (pers. com., 1992) of the contract relationships of

the Florida-Georgia state line. The Ochlockonee Forma- the Marianna/Glendon Limestones through the rest of

tion may be as thick as 1200 feet (366 m) in Gadsden the younger Vicksburgian in Mississippi is diametrically

County, Florida. Evidently the Gulf Trough served as a opposed to those interpretations of the correlative sec-

basinthat was rapidly filled with deep-water, fine-grained tions presented in this report. That is, in the Mississippi

carbonates during the Early Oligocene. If the Suwannee Vicksburgian section, the Marianna/Glendon contact is

C"!Irrent had not weakened significantly but remained a perceived to be disconformable whereas the Glendon/

strong current as during the latest Eocene, the accumula- Byram and Byram/Bucatunna contacts are perceived as

tionofdeep-watercarbonatesduringtheEarlyOligocene being gradational and conformable. We have no expla-

would have been impeded.

nation for these differences in interpretations at this time.

119

Bumpnose-Red Bluff-ForestHill depositional sequence
There are no known deposits outside of the Gulf Trough in Georgia that are thought to be correlative with the Red Bluff Clay of Mississippi and Alabama or the Bumpnose Limestone ofAlabama and Florida. TheOcalalike (but glauconitic) Bumpnose Limestone has not been found in Georgia. Georgia deposits that are closest in age to the Red Bluff, outside of the Gulf Trough, are the Ocmulgee Formation in the vicinity of Hawkinsville (whichisinterpreted to beyoungest Jacksonianbutwithin the Cassigerinella chipolensis-Pseudohastigerina micraZone) and the overlying, middle Vicksburgian Marianna Limestone. The apparent absence of the Bumpnose-Red Bluff stratigraphic interval on the continental shelf in Georgia is problematic. Although it is interpreted that the basal Oligocene,Red Bluff stratigraphic interval is off-lap of the latest Eocene, Shubuta high stand of the sea in the southeastern United States, the Marianna/Glendon depositional sequence commonly is interpreted to be off-lap of the Red Bluff depositional sequence. However, the Marianna and Glendon Limestones are both present in centralGeorgia where the Bumpnose or Red Bluff-equivalent is absent.
One possible interpretation is that the MariannaGlendon depositional sequence is on-lap to that of the Red Bluff. That is, the Bumpnose-Red Bluff high stand of the sea neither equaled that of the previous Shubuta high stand nor that of the subsequent Ellaville-Glendon high stand. This is a valid interpretation across Mississippi as far east as St. Stephens Quarry in southwestern Alabama, where the open marine, continental shelf Mint Spring Formation or Marianna Limestone overlies the coastal marine or deltaic Forest Hill Sand or the relatively nearshore Red Bluff Clay with apparent disconformity.
However, farther east in Alabama, the correlative Bumpnose-Red Bluff carbonates contain an apparently deeper water and more diverse benthic foraminiferal fauna than that of the overlying Marianna or Glendon Limestones. This is consistent with the occurrence of a 15 feet (4.6 m) thick bed of Lepidocyclina-rich dolostone in the Bumpnose, stratigraphically between the underlying Ocala Limestone and the overlying Marianna Limestone in the interval133 feet to 150 feet in the Florida Geological Survey core Duncan Church 1 (W-11487)from Washington County, Florida. The Red Bluff-Bumpnose is also consistently thin in outcrop across Alabama, averaging roughly 15 feet (4.6 m) in thickness. This is consistent with the thickness of the dolostone interval in the Duncan Church core. The underlying Upper Eocene deposits and overlying Marianna Limestone are considerably thicker than the Red Bluff-Bumpnose depositional sequence in Alabama and Florida (Huddlestun, 1965; Huddlestun and Toulmin, 1965; Huddlestun, 1966).
It is noted here that there was a siliciclastic pulse

of sedimentation associated with this depositional se-
quence. Itis notlikely that the ForestHill Sand represents
strictly an off-lap, nearer shore sedimentary event because as far east as the Gulf Trough, all deposits of the
Bumpnose-Red Bluff-Forest Hill depositional sequence
are more sandy, argillaceous, or glauconitic than that of the underlying and overlying deposits. It is, therefore, interpreted here that the siliciclastic sedimentary pulse is real, and that the Mint Spring Formation and the lower glauconitic part of the Marianna Limestone in western Alabama represents the middle Vicksburgian fading of this event.
As a result of the above discussion, the working model in this report is that the Bumpnose-Red BluffForest Hill depositional sequence is off-lap of the underlying Upper Eocene deposits (also see Dockery, 1990), and the middleVicksburgianEllaville-Marianna-Glendon deposition sequence is off-lap of the Forest Hill-Red Bluff-Bumpnose depositional sequence. This is consistent with the lithology of the Bumpnose Limestone resembling more the lithology of the underlying Ocala Limestone and the offshore, Vicksburgian Florala Limestone than that of the overlying Marianna Limestone.
Georgia is relatively more tectonically stable than the eastern Gulf Coastal Plain and has experienced less subsidence and contains fewer stratigraphic intervals in the geologic column than that of western Florida, Alabama, and Mississippi (see Huddlestun and others, 1988, Huddlestun and others, in manuscript). It is suggested, therefore, that the continental shelf of Georgia during the Bumpnose-Red Bluff-Forest Hill depositional sequence may have been a surface of sedimentary bypass, that the shelfbottom occurred within the zone of base-level oscillation and the shelffloor was often sweptby currents (Fig. 55). Theworkingmodel ofthisreportis thatthe Suwannee Current was severely reduced after the terminal Eocene event and was again reduced after the Forest Hill-Red Bluff-Bumpnose depositional sequence. The current velocities on the shallower Georgia continental shelfduring the period in question may have been sufficientto impede sedimentation on the shelf. However, with the subsequent decline in the Suwannee Current, the currents on the Georgia continental shelf were insufficient to impede sedimentation. This is consistent with the absence of planktonic foraminifera in the Marianna and Glendon Limestones in Georgia in contrast to their abundance in the same formations in western Florida and Alabama.
The depositional situation was probably different within the Gulf Trough and deeper water Florida Platformfarther south. Thelower part ofthe Ochlockonee Formation in the Gulf Trough is the most argillaceous part of the formation and contains a foraminiferal fauna that is largely compatible with that of the deeper water facies of the calcareous "Red Bluff" in southwestern Alabama. The continued occurrence, however, of the Jacksonian Uvigerina cocoaensis in the lower Ochlockonee

120

N
t

Atlantic Ocean

n.
Gulf of Mexico

-~L--j \
"t~'

w ~, r-

0 H

2E0 "330

40 50
H

mile-' . :
5\u

Figure 55.

Paleogeographic reconstruction of Georgia and northern Florida during the Bumpnose-Red BluffForest Hill depositional sequence.

121

Formation appears anomalous until it is noted that the lower part of the Ochlockonee Formation represents an unusuallydeepwater CoastalPlaindeposit, evendeeper water than that of the Shubuta Clay in Mississippi and Alabama. In addition, the outer neritic Vicksburgian under the outer continental shelf of Georgia (cores AMCOR 6002 and TACTS cores A-D, F) contains this species in addition to other typical deep-water Vicksburgian benthic foraminifera and a planktonic foraminiferal suite of the Cassigerinella chipolensisPseudohastigerina micraZone. It is concluded here that the benthic foraminifer U. cocoaensis did not become extinct after the Jacksonian, but only during the late Jacksonian were water depths on the continental shelf sufficiently deep for this species to briefly colonize much of the shelf floor of the southeastern North American continental margin. After Jacksonian time, the species withdrew toward the outer shelf where deeper water conditions prevailed. The geographic range of this species on the continental shelfduring the Oligocene was possiblymore restricted because of progressively shallower water conditions on the continental shelfand a consequent narrowing of the shelf.
Similarly, it is likely that the basal Oligocene, Bumpnose-Red Bluff-Forest Hill depositional sequence is present farther south on the Florida Platform. Because the limestone lithology of this interval is elsewhere similar to that of the underlying Ocala, the Bumpnosee-Red Bluff-Forest Hill depositional sequence of peninsular Florida may not have been differentiated lithostratigraphically from that of the underlying Ocala Limestone (see Banks, 1976b; Hunter, 1976).
It would appear that with the first high stand of the sea during the Oligocene (Bumpnose-Red Bluff-Forest Hill depositional sequence), the water depth in the Gulf Trough may have been sufficiently deep to. still accommodate a gradient current in the Gulf Trough. However, as with the earlier reduction in the Suwannee Current at the end of the Midwayan (Huddlestun and others, inmanuscript),thereductionof theSuwannee Current at the end of the Eocene was a one way event. When the inertia of the augmented Florida Current became established during the low stand of the sea at the end of the Eocene, additional water was not quickly diverted through the Suwannee Strait with the following high stand of the sea. Evidently the Suwannee Current had been so reduced by the terminal Eocene low stand of the sea that it could no longer exist as a strong gradient current.
Once sea level had risen during the earliest Oligocene and the Suwannee Current was no longer confined by the flanks of the Gulf Trough, the current appears to have risen out of the confines of the marine channel, and spread out as a shallow, broad current (Fig. 56a and 56b). Thick deposits of relatively deep water, argillaceous, foraminiferal carbonates appear to have

been deposited in the Gulf Trough at this time. It is not clear to what extent the Suwannee Current may have existed as a small gradient current or was in part a drift current. There does not appear to have been a reduction in hydrostatic head between the Gulf of Mexico and Atlantic Ocean at the end of the Eocene because any change in head would also have had a similar impact on the Florida Current. However, there is no evidence of a reduction of the Florida Current on the Blake Plateau at the end of the Eocene (Popenoe, pers. com., 1991). Therefore it is concluded that during the early and middle Vicksburgian (Red Bluff through Glendon deposition), the Suwannee Current continued to flow across the Suwannee Strait area as a further reduced gradient or drift current.
Post-Bumpnose-Red Bluff hiatus
A eustatic low stand of the sea is postulated to separate the Red Bluff depositiona! sequence from that of the overlying Marianna-Glendon. At numerous localities in Alabama and northwestern Florida, the Marianna Limestoneoverlies the BumpnoseLimestoneorRed Bluffequivalent carbonates with a marked discontinuity and lithologic change. Because there are no known Red Bluffequivalent deposits outside of the Gulf Trough in Georgia, the position of the strand line in the Suwannee Strait area during this low stand of the sea can only be conjectural (Fig. 57). It is possible that the low stand of the sea that terminated the Red Bluff-Bumpnose depositional sequence may have been as low as that of the.preceding terminal Eocene low stand. If so, the strand line of this low stand probably would have occurred somewhere between Hawkinsville, Georgia, and the northern flank of the Gulf Trough.
It is expected that the Suwannee Current would have been strictly confined to the Gulf Trough again at this low stand of the sea and one would expect to find a physical discontinuity within the lower part of the Ochlockonee Formation within the trough. However, there is no indication of a sedimentation break within the lower part of the Ochlockonee Formation within the deeper parts of the Gulf Trough.
On the other hand, on the northern margin of the trough in northwestern Colquitt County in the Georgia Geologic Survey core Colquitt 11 (GGS-3545), there is a marked disconformity at 490 feet that may represent the low stand of the sea between the Bumpnose-Red BluffForest Hill depositional sequence and the EllavilleGlendon-Marianna-Mint Spring depositional sequence (see McFadden an.d others, 1986, p. 333-223). Typical dolomitized Ochlockonee Formation occurs above this discontinuity and the basal few feet of the unit is phosphatic and glauconitic. The lithology of the underlying limestone is not typical Ochlockonee and is chalky and

122

NW

Gulf

Trough

=

Marianna- Glendon Ellaville NW

Gulf Trough

SE Sea Level
SE Sea Level

End of Red Bluff NW

Gulf
(::Trough ~=) SUWANNEE CURRENT

Red Bluff-Bumpnose NW

Gulf Trough

SE Sea Level
SE Sea Level

End of Jacksonian NW

Gulf Trough

Late Jacksonian

SE Sea Level

0' 100' 200' 300' 400'
500' 600'

Figure56a.

Model of seq~ential diminishing and termination of the Suwannee Current in the Gulf Trough from the latest Eocene through the Oligocene.

123

NW

SE

Gulf
======~~~~~~~~
End of Vicksburgian

NW

SE

v -Gulf
~ Sea L~ evel ~~~~ Troug~ h ,..)'u~ wann~ ee C~ urrent~~~~.A
=
Okapilco-Bucatunna

NW

SE

- ~ ======~eSa~Leve) Gulf Suwannee Current
Wolf Pit

NW

SE

Gulf Suwannee Current
~ Sea L~ evel ~~~Troc ugh I~ ll' ~~~~~~

Suwannee

V!J'

NW

SE

=r - - Gulf
~S~e~a~L~e~ve~I============~Ti~ro~u~g~h~'~S~uw=a=n=n=ee==C=u=rr;en;t;:::::~~"
=
Suwannacoochee

Figure56b.

Model of sequential diminishing and termination of the Suwannee Current in the Gulf Trough from the latest Eocene though the Oligocene.

124

N
t

Atlantic Ocean

Gulf of Mexico

' ~

VOLUSIA

1-~. 0 10 20 30 40 50 E3 H

r-
\J

Figure 57.

Paleogeographic reconstruction of Georgia and northern Florida during the post-Bumpnose-Red Bluff hiatus.

125

cherty. It does, however, contain a typical Ochlockonee foraminiferal fauna in its lower part. It is interpreted here that the lower cherty, chalky phase of the Oligocene channel fill at this site is Red Bluff-equivalent, and the overlying dolomitized Ochlockonee Formation and Florala Limestone represent the Ellaville-GlendonMarianna-Mint Spring depositional sequence (Pl. 3).
Based on the preceding discussion, during the Red Bluff-Marianna low stand of the sea the Suwannee Current was so diminished that, when confined to the Gulf Trough, it was too feeble to influence bottom conditions in the deepest parts of the trough. However, the Suwannee Current remained substantial enough that in shallower water environments along the margins of the Gulf Trough, it impeded sedimentation when it was confined to the marine channel).
Ellaville-Glendon-Marianna-Mint Spring depositional sequence
During the subsequent high stand of the sea (Fig. 58), the middle Vicksburgian Florala Limestone Member of the Bridgeboro Limestone, Marianna Limestone, and Glendon Limestone were deposited north of the Gulf Trough and the Ellaville Limestone south of the Gulf Trough. The Bridgeboro Limestone was deposited along the flanks of the Gulf Trough in the influence of the Suwannee Current whereas the Florala Limestone Member was deposited mainly seaward of the Vicksburg Group and beyond the direct influence of the Suwannee Current in the Gulf Trough. These formations are included in the same depositional cycle because the Marianna and Glendon are conformable in Alabama and Georgia, because the Ellaville Limestone has generally been correlated with the Glendon Limestone (Cooke and Mossom, 1929), and because the Florala Limestone Member grades laterally into typical Bridgeboro Limestone.
The Marianna and Glendon Limestones in Georgia occur along the right bank of the Ocmulgee River below Hawkinsville, Pulaski County, Georgia (also see Pickering, 1970; Huddlestun and others, 1974; Glawe, 1974;thisdocument,p.16, 18-20,21). These exposures are considered to be outliers, and the formations are thought not to be physically continuous in the subsurface due to subsequent erosion and dissolution of limestones in the DoughertyPlain area northeastofJacksonCounty,Florida. In addition, it is not likely that the Marianna and Glendon Limestones had been deposited appreciably farther north than the vicinity of Hawkinsville. In northernmost Bleckly County, Georgia, north of Hawkinsville, the Shellstone Creek beds, a series of thinly stratified, argillaceous fine sands of Barnwell Group appearance but with silicified Oligocene macrofossils (Clypeaster rogersi and Rhyncholampas gouldii) occur in the stratigraphic position of the Marianna and Glendon

Limestones at Hawkinsville. The Marianna and Glendon Limestones at
Hawkinsville appear to be conformable and gradational, and the benthic foraminiferal faunas do not appear to reflect any substantial differences in the temporal or bathymetric aspects of the two formations. It is for these reasons that the Marianna and Glendon Limestones are postulated to have been deposited during a single eustatic high stand of the sea. Their differing lithologies are a reflection ofa temporallyabrupt changein thecontinental shelf water mass conditions from a relatively long term, stable water mass (reflected in the deposition of the Marianna Limestone), to periodically changing to a periodically varying water mass oscillating with respect to its oceanographic conditions (reflected in the deposition of the Glendon Limestone). That is, periodic changes resulted in the typical ledge and re-entrant characteristic of the Glendon Limestone. This quality is also present in the Bridgeboro Limestone at its type locality but on a largerscale (Fig. 24). Because the basal Vicksburgian, Red Bluff-equivalent carbonates and Bumpnose Limestone also exhibit this ledge and re-entrant characteristic, similar shelf water-mass conditions may have existed during the deposition of both the older Bumpnose Limestone and the younger Glendon Limestone.
The Marianna and Glendon Limestones do not occursouthand east of the Hawkinsvilleexposures. Near Cochran in Bleckley County and as far south as Abbeville in Wilcox County, Georgia, the Bridgeboro Limestone occurs in the stratigraphic position of the Marianna and Glendon Limestones (Pl. 1). The Bridgeboro Limestone in the Ocmulgee River area appears to be laterally continuous with the Bridgeboro Limestone in its type area in that there are numerous exposures of the Bridgeboro Limestone between the type area and the Ocmulgee River.
Between Decatur County, Georgia, and Washington County, Georgia, there is a gap in the known occurrence of the Bridgeboro Limestone. It is observed that the Bridgeboro Limestone is not known to occur in Jackson County, Florida (one cannotinterpret Bridgeboro lithology in Moore, 1955), butat Duncan Church in Washington County, Florida, the Bridgeboro Limestone gradationally overlies the Marianna Limestone.
The Marianna Limestone is not known to occur between the vicinity of Hawkinsville, Georgia, and Jackson County, Florida. Presumably the absence of the Marianna from this area is due to subsequent erosion or dissolution.
South of the Gulf Trough in Georgia and the northern peninsula of Florida, the type section of the Ellaville Limestone is correlated with the Glendon Limestone. As has been described earlier in thi~ report, the Rotularia vernoni Zone is present on the Suwannee River and appears conformable with the overlying Ellaville

126

N

t

PIEDMONT

? .

TAYLOR

DIXIE

Gulf of Mexico

0 10 20 30 40 50
H H H

miles

."

81

C')

I

,. 0

0

"tJ
m
.:.c,

0
:c
s:
~31
l>
-f

0
z

Atlantic Ocean

Figure 58.

Paleogeographic reconstruction of Georgia and northern Florida during the Ellaville-GlendonMarianna-Mint Spring depositional sequence.

127

Limestone. It is also noted that at 39 feet in the Florida Geological Survey core Ellaville 1 (W-10657), taken at Ellaville, the Ellaville Limestone disconformably? overlies limestone of Ocala appearance that contains .abundant Lepidocyclina sp. and Nummulites sp., similar to the exposures down river. If the Rotularia vernoni Zone is lowestOligocene,Red Bluff-equivalent,then theMarianna stratigraphic position probably occurs in a disconformity or in a condensed section at Ellaville. There may be considerable topographic relief on the top of the Eocene or basal Oligocene (Red Bluff-equivalent) in that area.
The Marianna-Glendon stratigraphic positions are postulated to occur within the Ochlockonee Formation within the GulfTrough. However, as yet there is no biostratigraphic data from the Ochlockonee Formation that explicitly indicates correlation with any part of the Vicksburgian Stage other than lower or middle Vicksburgian, Red Bluff through Glendon. In addition, there is no evidence of a physical discontinuity or hiatus within the middle and lower parts of the Ochlockonee Formation along the axis of the GulfTrough. However, as discussed above (p. 120, 122, 126), there is evidence for a disconformity within the Ochlockonee Formation on the northern margin of the Gulf Trough that appears to occur in the stratigraphic position of Marianna/Red Bluff disconformity. The lithology of the formation above this disconformity is typical dolomitized Ochlockonee. This dolomitic Ochlockonee interval also grades up-section into limestone that is indistinguishable from the Florala Limestone, again supportingcorrelationwith the Glendon Limestone.
In Georgia and peninsular Florida, all of the lower and middle Vicksburgian (Red Bluff through Glendon stratigraphic intervals) are restricted to the region west of the vicinity of the Peninsular Arch (Fig. 58)(Huddlestun and others, in manuscript). No Oligocene of this age is known to occur in eastern Georgia or northeastern Florida although it is possible that the lower part of the undifferentiated calcareous sand/sandy limestone formation within the northeastern extremity of the Gulf Trough in Georgia may represent lower or middle Vicksburgian deposits. On the other hand, the lower or middle Vicksburgian does occur offshore on the outer continental shelf of Georgia in the relatively deep-water Cooper Formation (p. 83-84).
The presence ofmiddleVicksburgian (Glendon/ Marianna-equivalent), relict Barnwell-type (coastal marine), nearshore deposits in the vicinity of the Ocmulgee River in Houston and Bleckley Counties in central Georgia (Fig. 9) indicates not only a similar depositional environment but also a similar spatial distribution (and shoreline position) to the Late Eocene. As during the Late Eocene, the positions of the shorelines during the early and middle Vicksburgian must be inferred indirectly because there seems to be no surviving Vicksburgian

shoreline deposits in Georgia. If the shoreline during the early and middle Vicksburgian (earliest Oligocene) did occur near the Fall line (Figs. 54, 57), a band of nearshore to coastal marine .Oligocene sediments at least 20 to 30 miles (32 to 48 km) across must have been removed by erosion in Georgia prior to the Miocene.
Evidence concerning the nature ofthe Suwannee Current during the middle Vicksburgian can be gleaned from the Bridgeboro Limestone. Modern rhodolith accumulations occur near shelf breaks with strong currents. In the case of the Bridgeboro Limestone, the current energy is presumed to be the Suwannee Current flowing from the Gulf of Mexico into the Atlantic Ocean. There are other hypothetical sources of current energy to produce the rounded rhodoliths, but the continued existence of a current above the Gulf Trough, the proximity of the Bridgeboro Limestone to the Gulf Trough, and the occurrence of the limestone only on the flanks of the trough point to the Suwannee Current as the source of energy. It is hypothesized here that the older formations in the vicinity of the Gulf Trough are non-rhodolithic because the Suwannee Current previous to the Oligocene had been a strongly-focused current and the bottom environment that was in contact with the current was below the photic zone. Other formations were deposited too far from the current for rhodoliths to flourish.
The abundance of rhodoliths in the Bridgeboro Limestone is taken, then, to indicate the presence of a current flowing from the Gulf of Mexico into the Atlantic Ocean during middle Vicksburgian time. Based on the width of the Bridgeboro Limestone subcrop belt, both south and north of the Gulf Trough, the current spread out from roughly 15 miles (24 km) across in the Colquitt County area during the Late Eocene, to very roughly 45 miles (72 km) across in the same area during the Early Oligocene (Fig. 56a and 56b)(also see Huddlestun and others, in manuscript). The fact that the current affected only shallow water in the strait allowed the Gulf Trough to continue to rapidly fill with finely granular, foraminiferal (mainly smaller benthic foraminifera), argillaceous, relatively deep-water calcareous sediments. This resulted from the raising of sedimentational base level within the Gulf Trough above the bottom the trough, permitting net accumulation of sediments.
The shoaling and spreading out of the Suwannee Current after the Eocene is problematic. It could be interpreted as the transformation of the Suwannee Current from a gravity current to a drift current, or as a diminishing of the hydrostatic head between the Gulf of Mexico and Atlantic Ocean as discussed earlier.
Suwannacoochee low stand of the sea
Following the deposition of the middle Vicksburgian Glendon, Bridgeboro, and Ellaville Lime-

128

stones, during the Late Oligocene, there occurred the first cur north of the Gulf Trough. However, a thin, six inch

of a series of brief but drastic sea level drops that culmi- bed of chert occurs in the Suwannacoochee stratigraphic

nated in the subaerial exposure of most ofthe continental position at the top of the Bridgeboro Limestone and

shelf of southeastern North America (compare with below the overlying Suwannee Limestone in Rockhouse

Fisher and Ward, 1984)(Fig. 59). In most areas of the Cave in Crisp County, Georgia, approximately 40 miles

eastern Gulf Coastal Plain, this low stand of the sea is (64 km) north of the Gulf Trough. Both stratigraphic

represented by the disconformity between the Glendon position and the fact that the Suwannacoochee Dolostone

Limestone and Byram Formation, between the Glendon commonly contains minor amounts of chert suggests

Limestone and Bucatunna Clay where the Byram is ab- stratigraphic relationship between the chert bed in

sent (as at St. Stephens Quarry in Washington County, Rockhouse Cave and the Suwannacoochee. The origin of

Alabama), or between the Marianna Limestone and the chert is problematic and is not considered to have

Bucatunna Clay where both the Glendon and Byram are been primary. It may represent nondeposition and re-

locally absent (see Dockery, 1982, p. 21; MacNeil and placement of the top of the Bridgeboro Limestone during

Dockery, 1984, p. 22).

the Suwannacoochee low stand of the sea. Similarly, it is

South of the Gulf Trough in south Georgia and possible that the present patchy distribution of the

northwestern peninsular Florida, this stratigraphic inter- Glendon Limestone in the vicinity ofHawkinsville, Geor-

val is occupied by the Suwannacoochee Dolostone. The gia, may be the result of subaerial exposure and dissolu-

lowering of the sea associated with the deposition of the tion oftheGlendonin that area. Thus theSuwannacoochee

Suwannacoochee Dolostone had a profound sedimen- shore line probably occurred somewhere between

tary influence on the entire continental shelf perhaps as Hawkinsville and Cordele (Fig. 59). If the silicification is

far south as central Florida. During this apparently brief subaerial in origin, the shoreline would then have been

period, the entire continental shelf of Georgia and north- between Cordele and the Gulf Trough (south of

em Florida was under extremely shallow water, perhaps Cordele).

with near sea level conditions. Considering the vast areal

The water depth within the Gulf Trough during

extent of this shallow water shelf, the chemistry of the sea the Suwannacoocheelow stand of the sea is projected to

water must have deviated considerably from that of have been less than 300 feet (91 m) in Colquitt County but

normal sea waters. In addition, the common occurrence may have been as much as 400 feet (122m) in Berrien and

of rip-:up clasts in the dolostone indicates periodic and Coffee Counties and, therefore, the trough remained in

widespread high energy (storm?) conditions whereas the relatively deepwater (compare with Pl. 3). The general

presence of a sparse, low-diversity, depauperate fauna paleoenvironment within the Gulf Trough appears not to

suggests environmentally extreme conditions. In Geor- have been substantially altered during the

gia, there are occurrences of thinly bedded to laminated, Suwannacoochee event because, except for minor dolo-

very fine grained, gray dolostone that may be of primary mitization, the general lithology of the Ochlockonee For-

originin the lower part of the Suwannacoochee . In mation within this stratigraphic interval was not altered.

addition, the presence of laminated dolostone indicates i.e., it remained finely granular and bioturbated.

the absence of an infauna which further supports a bio-

Because the generallithologyof theOchlockonee

logically restrictiveenvironment for the Suwannacooch~ Formation within the Gulf Trough remained essentially

Dolostone.

constant across this interval, it is suggested that the

The prevailing dolomitization of the Suwannee Current continued to flow through the Gulf

Suwannacoochee is thought to be penecontemporaneous Trough during the Suwannacoochee low stand of the sea.

with deposition. The dolomitization is postulated to have The current may have maintained its strength but was

resulted from the sea water that reacted with the fine- strictly confined to the trough (Fig. 52, 56b, 59).

grained, calcitic material being deposited on the shelf in

a tropical to subtropical climate. It is suggested that the Suwannee-Byram depositional sequence

sea water on the shelf could have become somewhat

hypersaline. This chemically abnormal sea water also .

The high stand of the sea subsequent to the

couldhave been sweptoff the shelfas drift currents by the Suwannacoochee low stand resulted in the deposition of

easterly trade winds and the denser water could flow into the Byram Formation in Mississippi and the deposition of

the deeper Gulf Trough as gravity currents. Such a the Suwannee Limestone in Georgia and peninsular

scenario could account for the dolomitization in a persis- Florida (Fig. 60).

tent stratigraphic interval in the upper part of the

During this phase, the deposition of the Byram

Ochlockonee Formation.

Formation signaled the end of carbonate deposition in

The shelf north of the Gulf Trough may have the nearshore area of the eastern Gulf Coastal Plain. As

been bathymetrically higher than the shelf south of the yet I have not identified the Byram stratigraphic

trough. No Suwannacoochee Dolostone is known to oc- interval in southwestern Alabama. Those deposits that

129

Modern Fall
32"

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Atlantic Ocean

DIXIE

Gulf of Mexico

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Figure 59.

Paleogeographic reconstruction of Georgia and northern Florida during the Suwannacoochee low stand of the sea.

130

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Figure60.

Paleogeographic reconstruction of Georgia and northern Florida during the Suwannee-Byram depositional sequence.

131

have been correlated with the Byram, e.g., the thin bed of and containsconspicuousintraclastbeds (intraformational

"marl" overlying the Glendon Limestone at St. Stephens rip-up breccia). The latter is characteristic of shallow

Quarry, are correlated with the Bucatunna Clay on the water, high energy conditions and is suggestive of a

basis of the planktonic foraminiferal fauna. The upper- pronounced sea level drop during the final phase of

most part of the Florala Limestone in its type area maybe Suwannee Limestone deposition. Because the Suwannee

correlative with the Byram Formation and the Byram Limestone is at the top of the Oligocene section in all of

stratigraphic interval is thought to occur in the Florala Georgia outside of the Gulf Trough, the effects and posi-

Limestone throughout western Florida.

tioning of the subsequent eustatic fall in sea level that

TheSuwanneehighstandofthesea did notattain terminated Suwannee deposition cannot be observed in

the same high level as the previous high stands but outcrop. Howeve.r, additional Oligocene sediments are

conformed to the orderofprogressivelylowerhigh stands present within the Gulf Trough including sediments

of the sea through the rest of the Early Oligocene. The deposited during the subsequent low stand and follow-

Suwannee shore line must have been considerably north ing high stand of the sea.

of that of the Suwannacoochee. However, there is no

Within the Gulf Trough in Georgia, the upper

evidence of limestone or chert that contains the typical part of the Ochlockonee Formation is correlated with the

Suwannee "mealy" lithologyin the updip, Hawkinsville- Suwannee Limestone and Byram Formation. The upper

Cochran area in Georgia. In that area the youngest part of the Ochlockonee Formation is lithologically the

identifiable Oligocene is Glendon Limestone and the same as that below the dolomitized zone in the upper

correlative silicified Bridgeboro Limestone. In eastern Ochlockonee but it is generally more lithified and less

Georgia, on the other hand, silicified Suwannee Lime- argillaceous than the lower parts of the formation.

stone occurs as far north as the vicinity of the Burke-

Although no foraminifera have been extracted

Screven Counties line along Beaverdam Creek (Figs. 10 from the upper part of the Ochlockonee Formation, the

and 32). It appears likely that the Suwannee Limestone typical lithology would indicate conditions similar to the

and its coastal deposits were removed by erosion or older part of the Ochlockonee. Therefore, it is concluded

dissolution subsequent to deposition in the updip area. It thattheSuwanneeCurrentwasstillactivewithintheGulf

is also noted that fossiliferous chert that occurs at the top . Trough during the Suwannee-Byram high stand of the

of the section farther north in Burke County contains an sea (Fig. 56b).

Late Eocene fauna and not an Oligocene fauna. The

The Gulf Trough continued as a very constricted

Miocene Altamaha Formation is known to disconform- but still relatively deep water conduit for the Suwannee

ably overlie the Upper Eocene in Burke County. There- Current during the Suwannee high stand of the sea.

fore, if any Suwannee Limestone had once had been During this brief period, the deep-water Ochlockonee

present in Burke County, Georgia, either its silicified Formation contin~ed to be deposited within the Gulf

remnants have not yet been identified or it was subse- Trough but the remnant of the Suwannee Current must

quently removed by erosion or dissolution before the have been entirely confined to the Gulf Trough. The

Miocene.

Suwannee Limestone on either side of the Gulf Trough is

The depth of water on the continental shelf south barren of planktonic microfossils and has a low diversity,

of the Gulf Trough in Georgia and Florida was substan- shallowwaterbenthicmacro-andmicrofauna. Thedepth

tially less than it had been during preceding high stands of water on the shelf south of the Gulf Trough during this

of the sea and is thought to have been less than 50 feet (15 period was insufficient to sustain any large, directed

m). As a result, the peculiar Tethyan (Caribbean) benthic current or eddies thereof.

foraminiferal fauna characteristic of the earlier shallow

The model adopted here for the paleogeography

water Florida Bank, characterized especially by of the Georgia coastal area and continental shelf during

Dictyoconus (having survived the Late Eocene and earli- the Suwannee-Byram depositional sequence is as follows

est Oligocene inundations somewhere in refugia) became (Fig. 60): in central Georgia, the Suwannee shoreline

reestablished on the shelf south of the Gulf Trough. The probably occurred somewhere in the vicinity of

presence of the Suwannee Limestone north of the Gulf Hawkinsville or immediately south of Hawkinsville. In

Trough in central Georgia and east of the Gulf Trough in eastern Georgia, the Suwannee coastal area probably

eastern Georgia (Fig. 60), indicates that the Tethyan (Car- occurred in Burke County. It is possible that during

ibbean) Florida Bank foraminiferal fauna brieflyexpanded deposition of the Suwannee Limestone, limestone

its range. Previously it had been restricted to the Florida depositionalso occurred in the shoreline but it is also pos-

Bank.

sible there may have been a narrow, sandy coastal area.

The uppermost part of the Suwannee Limestone During the Suwannee high stand of the sea, and only during

in outcrop (especially along the Withlacoochee River in thishighstand,it appears that a modifiedFloripa Bank faunal

Brooks and Lowndes Counties, Georgia) differs from province may have extended all the way from the earlier

typical Suwannee Limestone in that it is more stratified Horida Bank in the Aorida peninsular area in the south,

132

northward to the coastal area of North America in Georgia (Figs. 48,49). During this brief, diminished high stand of the sea, there would have been a mingling of eastern Gulf Coastal Plain, southern Atlantic Coastal Plain, and Florida Bank faunas in the coastal waters.
In the vicinity of the modem Oconee River, however, the nearshore, subsurface, undifferentiated calcareous sand and sandy limestone suggests that the paleoOconee River flowed near its modem course and was a considerable local source of siliciclastics during the Oligocene. Physical correlation indicates that at least the upper part of this sandy sequence is correlative with the Suwannee Limestone and, therefore, presents a siliciclastic, coastal marine phase of the Suwannee Limestone. The abrupt appearance of siliciclastics in this part ofthe Vicksburgianis compatiblewith the Atlantic Coastal Plain suite of formations where the Lazaretto Creek Formation indicates a siliciclastic source from the north, and with the eastern Gulf Coastal Plain Vicksburgian where the Byram Formation presents an abrupt influx of siliciclastic sediments. The earlier Glendon depositional phase represents the greatest westward expansion of carbonate deposition during the Tertiary of the southeastern United States. The sudden but minor increase in siliciclasticdeposition during the Byram-Suwanneedepositional sequence is interpreted as representing a second pulse of siliciclastic deposition during the Oligocene. The sandy phase of late Vicksburgian deposition has not yet been identified in the Vicksburgian residuum west of the vicinity of the Ocmulgee River, nor east of the vicinity of the Ogeechee River.
Wolf Pit low stand of the sea
The second in the series of sudden, drastic but brief sea level falls followed the deposition of the Byram Formation in Mississippi and the Suwannee Limestone in Georgia and Florida (Fig. 61). This low stand of the sea was more severe than the preceding low stands and the Gulf Trough briefly became a vast, shallow water embayment projecting obliquely into the Coastal Plain of southeastern North America (Fig. 61). The Wolf Pit low stand of the sea also represents the termination of Oligocene sedimentation in Georgia outside of the of the Gulf Trough and outer continental shelf.
This fall in sea level was even more severe than that of the Suwannacoochee low stand and resulted in the deposition of the Wolf Pit Dolostone within the Gulf Trough and the probable subaerial exposure of the continental shelf outside of the Gulf Trough in Georgia and Florida. Within the Gulf Trough, the Suwannee-equivalent Ochlockonee Formation is gradationally and conformably overlain by the Wolf Pit Dolostone. The Wolf Pit is lithologically similar to the Suwannacoochee Dolostone but it occurs in a stratigraphically higher position and at

much lower elevations than the Suwannacoochee and, therefore, is not considered to be correlative with the Suwannacoochee (PI . 3). The Wolf Pit Dolostone is considered to represent the low stand of the sea following the deposition of the Suwannee Limestone on the continental shelf adjacent to the Gulf Trough. In Coffee County, the Wolf Pit Dolostone appears to have been deposited in a very shallow water, restricted environment, probably near sea level similar to the Suwannacoochee Dolostone. The Wolf Pit in the type core in Colquitt County appears to have been deposited largely as fossiliferous and bioturbated limestone that was penecontemporaneously or subsequently dolomitized. The Gulf Trough (Chattahoochee Embayment) is broader in Colquitt County than in Coffee County so the Wolf Pit Dolostone may have been deposited in more open marine cond.itions and in deeper water in Colquitt County than in Coffee County.
The depth of sea water within the Gulf Trough must have been inadequate to pass any more than a trickle of water through it and, if the eastern end of the trough was higher in elevation than the western end, it is likely that the eastern end of the trough was also exposed subaerially. Therefore there would have been no water passage during theWolfPit event. Ifthe easternend of the trough was subaerially exposed during the Wolf Pit event, the Gulf Trough would have been a long, narrow, linear embayment like a vast estuary. The shelf on either side of the trough would have been subaerially exposed, and the former Florida Bank was a peninsula for the first time (Fig. 61) since the early Late Cretaceous. The Suwannee Current, therefore, must have been finally terminated during this low stand ofthe sea (Fig. 56b). The outer, southwestern part of the Chattahoochee Embayment probably was the siteofeither shallow water limestone deposition, or of nondeposition, depending on the degree of up-welling of the dying Suwannee Current against the continental margin of North America.
During the Wolf Pit low stand of the sea, the emergent continental shelf outside of the Gulf Trough must have been covered with land, swamp, or marsh vegetation because of no established terrestrial drainage patterns (Fig. 61). Shallow water marine conditions prevailing within the Gulf Trough indicate that the shoreline during this event must have occurred deep within the trough along the northern and southern flanks. It is conjectured here that the thinning of the Byram Formation in eastern Mississippi (Johnson, 1982) and its absence in outcrop in southwestern Alabama is the result of subaerial erosion during the severe low stand of the sea following the deposition of the Byram Formation.
Okapilco-Bucatunna depositional sequence
With the subsequent rise in sea level following

133

N
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0 10
H

20 30 40 50
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miles

Figure 61.

Paleogeographic reconstruction of Georgia and northern Florida during the Wolf Pit low stand of the sea.

134

the Wolf Pit low stand of the sea, a normal marine Trough in Georgia during the Okapilco high stand of the

environment became reestablished within the Gulf sea, then the terrane outside of the trough in Georgia and

Trough. In the eastern Gulf Coastal Plain, the post-Byram northern Florida would have remained near or above sea

(post-Suwannee) high stand of the sea is represented by level and probably had the appearance of vast coastal,

the deposition of the Bucatunna Clay in nearshore areas freshwater swamp. If, on the other hand, the sea was not

in Mississippi and Alabama, and in offshore areas by the confined to the trough, then the shelf outside of the

upper part of the Florala Limestone in the western pan- trough would have been under extremely shallow water.

handle of Florida. In Georgia this sedimentary interval is Such deposits that may have been deposited (Bucatunna

represented by the Okapilco Limestone within the Gulf Clay? or dolostone) could have been removed by erosion

Trough (Fig. 62). The Okapilco Limestone is a relatively prior to the Miocene. There is evidence that Bucatunna

shallow-water deposit that contains abundant colonial Clay may have been deposited in deeper water along the

corals and therefore, must have been deposited well gently sloping northern flank of the Gulf Trough in

within the photic zone.

Georgia because the weathered clay overlying the

The deposition of the granular, commonly fine Bridgeboro Limestone at the type localityofthe Bridgeboro

grained, bioturbated carbonates of the Middle Eocene lithologically resembles the Bucatunna Clay and con-

through most of the Early Oligocene did not resume tains silicified Oligocene mollusks.

during the Okapilco high stand in the Gulf Trough.

Rather, a more coarsely granular limestone that was Post-Vicksburgian-pre-Chickasawhayan low stand of

replete with colonial corals was deposited. The biota of the sea

this limestone is of low diversity. In addition, although

the benthic foraminifera indicate that open marine condi-

There is no known marine record in Georgia for

tions again prevailed in the trough, the diversity of the the subsequent Oligocene. At all known sites outside of

population is low and is indicative of only moderate the trough, the Suwannee Limestone is the youngest

water depths, consistent with the premise that the Gulf known unweathered formation that occurs at the tops of

Trough had been largely filled by the end of the the local sections. The youngest unweathered Oligocene

Vicksburgian.

-deposits in Georgia occur only within the Gulf Trough.

It is unlikely that the Okapilco shoreline was far All subsequent information on the Oligocene history of

from the flanks of the Gulf Trough (Fig. 62). Rather, it the Gulf Trough has been lost during weathering and

appears likely that the shore line in Georgia for the erosion events prior to the Miocene. A core taken by the

Okapilco-Bucatunna high stand lay near the upper flanks Florida Geological Survey from the Florida panhandle in

of the trough.

Walton County (Mathis 1; W-8102) near the town of

Farther southwest in the Chattahoochee Florala in Alabama, however, contains a richly foramini-

Embayment in Florida, limestone deposited during this feral, late Vicksburgian and Chickasawhayan succession

high-stand resembles the Bridgeboro Limestone, though that can be employed to interpret the later Oligocene

with anastomosing algae rather than rhodoliths. It is geologic history of Georgia and of the Gulf Trough (Fig.

concluded, therefore, the Suwannee Current is rejuvinated 63). In the Mathis 1 (W-8102), the section from327 feet to

and substantial current energy was expended by the T.D. at375 feetconsistsofdenselypacked, subcoquinoid,

Suwannee Current as it encroached on the continental Lepidocyclina-rich Florala Limestone. Above 327 feet the

shelf of Florida. That the Gulf Trough still served as a limestone is unconsolidated and less densely packed

conduit for the Current is indicated by the presence of a with Lepidocyclina but contains a rich and diverse suite of

substantial suite of planktonic foraminifera in the planktonic and benthic foraminifera. The core above 287

Okapilco Limestone in Coffee County, Georgia. The feet also consists of hard, indurated, coarsely fossilifer-

current, although feeble, must have been strong enough ous, Lepidocyclina-rich limestone.

for open-marine water-mass conditions to prevail as far

The top of the Lepidocyclina-rich Florala Lime-

northeast as Coffee County. A directed ocean current, stone occurs at 274 feet and is a useful stratigraphic

therefore, became reestablished in the Gulf Trough after marker in the panhandle of Florida. The limestone from

the Suwannee Current had ceased during the Wolf Pit 274 feet to 251 feet is the limestone unit exposed at

low stand of the sea. A feeble current reentering the Gulf Natural Bridgein northern Walton County, Florida (Cooke

Trough is not surprising in that the descendent of the and Mossom, 1929; Cooke, 1945; Puri and Vernon, 1964)

Suwannee Current, the modern Loop Current, still exists and is a calcareous subdivision of the Bucatunna Clay.

-in the eastern Gulf of Mexico and if the proper geologic This limestone is generally slightly argillaceous, finely

and geographic conditions were to become reestablished granular with scattered Lepidocyclina, Nummulites, and

in Georgia and northern Florida in the geologic future, Pecten poulsoni byramensis. A thin feather-edge of calcar-

there could be a rebirth of the Suwannee Current.

eous Bucatunna Clay occurs from 252 feet to 245.5 feet in

If the sea were restricted largely to the Gulf the core Mathis 1 and is overlain 1.5 feet of argillaceous

135

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Figure62.

Paleogeographic reconstruction of Georgia and northern Florida during the Okapilco-Bucatunna depositional sequence.

136

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Figure63.

The Oligocene geologic section exposed in the Florida Geological Survey core Mathis 1 (W-8102) 137

dolostone. The dolostone is interpreted to represent a eustatic low stand of the sea.
The Chickasawhay Formation abruptly overlies thedolostoneat244feet. Above244feettheChickasawhay section consists of unconsolidated, slightly argillaceous and micaceous, granular limestone that grades upward into calcareous clay at 218 feet. The upper part of this clay bed is dolomitic and the clay in turn is overlain abruptly by dolostone at 201 feet. The dolostone is disconformably overlain by Lower Miocene sands at 192 feet (Also see Huddlestun, 1984, Fig. 21).
This section is interpreted as follows: Based on planktonic foraminifera the section from the top of the Florala Limestone at 274 feet to T.D. at 375 feet is correlated with the Byram Formation or Glendon Limestone . The local top of Pseudohastigerina micra occurs at 304 feet and that of Globorotalia increbescens-Globigerina ampliapertura at 290 feet. The changing benthic foraminiferal population above 317 feet indicates a progressive shoaling of the sea. The discontinuity at 274 feet is interpreted as representing the Wolf Pit low stand of the sea arid is correlative with the Bucatunna/Byram disconformity (and the WolfPit Dolostone. Thelack ofdolomitization and other disconformity characteristics indicates that the continental shelf near Florala at this time in the Oligocene was in sufficiently deep water relative to the Suwannee Strait region to the east to mask the drastic effects of the Wolf Pit low stand.
The benthic foraminifera below 300 feet in the Mathis 1 (W-8102) are indicative of much deeper water than the benthic foraminifera from the type locality of the Byram Formation. The deeper water benthic foraminiferal populations below 300 feet in the core Mathis 1 are more similar to the benthic foraminifera of the Red Bluff Clay, Marianna Limestone, and Glendon Limestone of southwestern Alabama (St. Stephens Quarry and Little Stave Creek). However, the benthic foraminifera at 276 feet, near the top of the Florala Limestone in the core, indicate considerably shallower water, yet deeper still than that at the type locality of the Byram or of the Glendon at Vicksburg, Mississippi.
It is interpreted here that the close correlation between the top of the Lepidocyclina-rich Florala Limestone and the local extinctions of Pseudohastigerina at 304 feet and Globorotalia increbescens and Globigerina ampliapertura at 290 feet is significant. It is suggested here that the Wolf Pit low stand event not only approximates the base of the Bucatunna but also the boundary between the Globigerina ampliapertura and the Cassigerinella chipolensis-Pseudohastigerina micra Zones. It is also suggested that the subsequent consistent absence of the Globorotalia increbescens end-member of the plexus represents the extinction of that end-member, and the surviving end-member, G. ampliapertura, must have adopted a deeper-water habit because it too is consistently absent in

the youngest, relatively planktonic foraminiferal rich, Vicksburgian deposits of the southeastern United States.
The Bucatunna Clay occurs in the interval 274 feet to 244 feet in the Mathis 1 (W-8102) and the interval 251 feet to 245.5 feet is represented by typical but calcareous Bucatunna Clay. The benthic foraminiferal suite within this interval is interpreted as originating in a significantly shallower water environment than that of the underlying Lepidocyclina-rich Florala Limestone, but still deeper water than the foraminiferal suites from outcropping Bucatunna Oay. It is concluded, therefore, that aswasthecaseintheSuwanneeStraitregion,theOkapilcoBucatunna high stand of sea in the eastern Gulf Coastal Plain was considerably lower than that of the previous Oligocene high stands of the sea.
Based on the occurrence of dolostone gradationally overlying the Bucatunna Oay at 245.5 feet in the core Mathis 1{W-8102) and in turn beingoverlain with a sharp contactbycoarsely fossiliferous limestone, it is concluded that the post-Vicksburgian (post Okapilco-Bucatunna) low stand of the sea (TA4.5 of Haq and others, 1987) was considerably lower than the previous Wolf Pit low stand. The continental shelf in the Florala area was exposed to very shallow water conditions that resulted in penecontemporaneous or subsequent dolomitization of the sea floor sediments. If this interpretation is correct, then the low stand of the sea (TA4.5) following the deposition of the Okapilco Limestone in the Gulf Trough was even lower than that of the Wolf Pit low stand. This postVicksburgian low stand would have not only exposed the Suwannee Strait region to subaerial erosion but also would probably have left the floor of the Gulf Trough subaerially exposed as well (Fig. 64). If there were topographic relief on the floor or the trough, i.e., highs and lows, then it is likely that the Gulf Trough could have contained a series of lakes and large, interconnecting streams. Through-flowing rivers could have become established at that time.
The only other evidence that I am aware of concerning the post-Vicksburgian low stand of the sea is the occurrence of the Waynesboro Sand of eastern Mississippi (Johnson, 1982). The Waynseboro Sand appears to be associated with the regressive stage of the Bucatunna Clay. Johnson (1982) reported thatthe Waynesboro Sand not only appears to grade latterally into the Bucatunna Clay but locally also disconformably overlies the Byram Formation:, the Glendon Limestone, and the Marianna Limestone.
Chickasawhay depositional sequence
The Chickasawhay Formation abruptly overlies the dolostone at the top of the Bucatunn~ Oay at 244 feet in the Mathis 1(W-8102)core. Evidentlythe Chickasawhay Formation was deposited in the depositional cycle that

138

----
N

t

PIEDMONT

Modern Fall
.... ...... "~....

''' "'
........
' .......
"' "

Gulf of Mexico

0 10 20 30 40 50
E3 E3 H

miles

Figure 64.

Paleogeographic reconstruction of Georgia and northern Florida during the post-Vicksburgianpre-Chickasawhayan low stand of the sea.

139

followed after some lag of time the low stand of the sea that terminated the Vicksburgian (TA4.5). The appearance of the planktonic fauna suggests a relatively long period of time had lapsed between the time of Bucatunna deposition and the time of Chickasawhay deposition.
The benthic foraminiferal fauna of the Chickasawhay Formation is indicative of'even shallower water conditions than the underlying Bucatunna section both in the Mathis 1 core and in outcrop in Mississippi and Alabama. To the east in Georgia then, if the high stand of the Chickasawhayan sea was noticeably lower than that of the earlier Okapilco-Bucatunna high stand, then much of the continental shelf south of the Gulf Trough must have remained subaerially exposed during the Chickasawhayan. The Gulf Trough would have existed as a narrow, shallow, linear embayment of the sea, a large estuary, ora river valley with a large estuaryat its southwestern end (Fig. 65). Most of the Georgia Coastal Plain would have been subaerially exposed and there probably occurred an incipient Florida peninsula to the south. In addition, it is likely that the terrane south of the Gulf Trough in Georgia and Florida remained a low elevation, fresh water plain reminiscent of the modem Everglades of Florida.
Thisscenariowould explaintheabsenceofknown Chickasawhayan deposits throughout Georgia outside of the lower Chattahoochee Embayment. The reports of shellyresiduurnofChickasawhayanageonthe Dougherty Plain sternsfrom correlationsby earlierworkersfrom the 1930's and 1940's and since then has not been supported by field work. The stratigraphic cross-sections on Pl. 3 are not consistent with the presence of any Chickasawhayan deposits outside of theGulf Trough in Georgia.
The Chickasawhayan, Upper Oligocene occurs only as deep water, outer neritic deposits in adjacent SouthCarolina, under the outer continental shelfofGeorgia (Ashley Member of the Cooper Formation), and possibly within the Chattahoochee Embayment in Florida. The interpretation of the Late Oligocene geology in the Suwannee Strait region, therefore, is problematic. There are two principle contributing factors to the problem of what happened during the later Oligocene. (1) My observations of high stands and low stands of the sea during the Oligocene are generally consistent with the eustatic sealevelcurvesofHaqand others (1987). However, Irecognize more high amplitude eustatic sea level fluctuations during the Early Oligocene than reported by Haq and others (1987). This is more consistent with the sea level fluctuation proposed by Baurn and Vail (1988) and Mancini and Tew (1990, 1991). (2) There is as yet no consensuson correlationbetween the cosmopolitan stage boundaries of the Oligocene and planktonic foraminifera zones. For example, Haq and others (1987) place
the Globigerina ampliapertura Zone within the middle part
of the Rupelianand place their TA4.5/TA4.4 boundary at
thetopoftheG.ampliaperturaZone. Thelowerpart of the

Globorotalia opima opima Zone, of which the
Chickasawhayan provincial stage is part, is partially in their Chattian Stage (Pl. 1),, This is consistent with the appearanceofthe stratigraphicrelationshipsbetween the upper part of the Vicksburgian and Chickasawhayan Stages in the southeast. That is, there appears to be no greater disconforrnity between the Chickasawhay Formation and Bucatunna day than there is between the Bucatunna Oay and Byram Fon.nation. On the other hand, there is considerably more faunal evolution betweentheplanktonic foraminiferaoftheChickasawhayan and Bucatunna, than between the Bucatunna and the Red Bluff, which bespeaks a greater time interval between the Chickasawhay and Bucatunna than between the Bucatunna and Red Bluff (PL. 1).
Hardenbol and Berggren (1978) included the G.
ampliapertura Zone in the Chattian and, therefore, all of the Globorotalia opima opimaZone is within their Chattian.
That interpretation is more compatible with the constitution of the Chickasawhayan planktonic foraminiferal suite than that of the Vicksburgian.
Post-Chickasawhay low stand(s) of the sea
The eustatic low stand of the sea following the deposition of the Chickasawhay Formation and Paynes Hammock Sand appears to have been unusually low relative to all of the Tertiary low stands of the sea that preceded it (Fig. 48). The post-Chickasawhay Formation low stand would appear to be that of TB1.1 of Haq and others (1987).
No preserved Oligocene deposits subsequent to the Chickasawhay and equivalent deposits are known from outcrop or cores from the Coastal Plain of Alabama, Georgia, Florida, South Carolina, or the continental shelf of Georgia and South Carolina. Based on the amplitudes of the eustatic sea level fluctuation of Haq and others (1987), it is most likely that the Coastal Plain of this region was subaerially exposed. This also includes the floor of the Gulf Trough and, as a consequence, there must have been at leasta practical Florida peninsula during the Late Oligocene. During this period of subaerial exposure of theGeorgiaand FloridaCoastalPlain,theentireSuwannee Strait region must have been a vast, low-elevation karst plain. The Gulf Trough would have been a large valleylike feature that may have contained a series of lakes of varying size with poor drainage between the lakes or was a large river valley. During the high stands of the sea during the latest Oligocene, it is possible that the trough could have been a vast estuary that either contained salt marshes or a continuous, brackish arm of the sea. The deposits associated with these environments, if they ever existed, must have been eroded and removed during the subsequent low stands. They may also have been removed during the earliest Miocene, Aquitanian re-

140

N
t
PIEDMONT
"C
m
:D "TI
0
:D
s::
l>
"""' 0
z

Gulf of Mexico

0 10 20 30 40 50

H H

H

miles

Figure 65.

Paleogeographic reconstruction of Georgia and northern Florida during the Chickasawhayan depositional sequence.

141

entrance of the sea into the trough. Based on the species constitution of the basal
Miocene planktonic foraminiferal fauna (see Huddlestun, 1988), there is even more faunal evolution between the Chickasawhayan and Aquitanian, than between the Vicksburgian and Chickasawhayan. This suggests either a greater span of time between the former than the latter or more intense extinction/evolution between the Chickasawhayan and Aquitanian. On the basis of the above discussion, I suggest that the TB1.1/TA4.5 cycle boundary of Haq and others (1987) occurs not at the base of the Chattian but in the early part of the Chattian, that the Globorotalia opima opima/Globigerina ampliapertura Zones boundary approximates the Chickasawhayan/ VicksburgianStagesboundaryand theChattian/Rupelian Stages boundary (Pl. 1).
According to this model, the extreme low stand of the sea, TBl.l, was not a sudden event as indicated by Vail and others (1977) and Haq and others (1987). Rather, it was preceded by a series of progressively lower low stands of the sea punctuated by progressively lower high stands of the sea. The culmination of these falling sea levels was the extreme low stand at the beginning of depositional cycle TBl.l. Haq and others (1987) show a progressive rise in eustatic sea level following the TBl.l low stand. These subsequent high stands, TB1.2 and TB1.3 consistofcyclesofprogressivelyhigher high stands of the sea punctuated by progressively higher low stands of the sea.
Because the GulfTrough extendsmore than three quarters of the way across the Coastal Plain of Georgia, it must have intercepted a number of large, Piedmontdrainingriversduring theOligocene low stands (and also during the Miocene low stands) of the sea. These rivers would have included the paleo-Chattahoochee, paleoFlint, paleo-Ocmulgee, and paleo-Oconee rivers. Even if the Gulf Trough intercepted only one major river of the size of one of the above rivers, the Gulf Trough would have become an over-sized river valley during the subsequent Oligocene low stands of the sea and, at most, a large estuary during the Late Oligocene high stands of the sea. As a result itis postulated here that during the low stands of the sea of the Late and post-Vicksburgian Oligocene (and during the sub8equent Miocene low stands), the Gulf Trough served as a large river valley system (Figs. 48, 64). Southwest of Coffee County, Georgia, the river system flowed southwestward into the Gulf of Mexico via the remnant of the Chattahoochee Embayment. The modem Ochlockonee River that flows southwestward along the southern margin of the Gulf Trough in Georgia and Florida may be the descendent of this Late Oligocene-Miocene river.
The floor of the Gulf Trough on the top of the Oligocene is topographically high in Coffee County, and it is interpreted that the Coffee County area (within the

Gulf Trough) was a drainage divide. To the southwest of Coffee County it is speculated, the Late Oligocene Gulf Trough river (paleo-Ochlockonee River) drained southwestward througp. the Gulf Trough into the Gulf of Mexico via the remnantof theChattahoocheeEmbayment. To the northeast of Coffee County, the Gulf Trough is thought to have been occupied by a large lake or inland swamp at this time. The paleo-Oconee River flowed into the basin from the north and tributary streams flowed into it from the northeast and southwest along the axis of the Gulf Trough (Fig. 48). This segment of the Gulf Trough drained into the Atlantic Ocean through the large river valley of the paleo-Altamaha River. It is unlikely that the Ocmulgee River was captured by the Oconee River during the Late Oligocene or Early Miocene because the Early Miocene marine transgressions (high stands of the sea) submerged the modern lower Ocmulgee/Oconee Rivers area. Subsequently, the fluvial Middle Miocene Altamaha Formation (of probable braided stream origin) blankets the area. Such a depositional environment on an active flood plain does not seem an appropriate place for stream capture by large streams. Yet curiously, and probably not coincidentally, the northeastward bend of the Ocrnulgee River occurs east of the topogrnphichigh within thetop alongthe buriedGulfTrough.
No siliciclastics are known to occur in any of the marine Chattahoochee Embayment Oligocene deposits in Florida (Huddlestun, 1984; Schmidt, 1984). Itis concluded, therefore, that the paleo-Ochlockonee River had no siliciclastic bed load during the Oligocene. It is also concluded that there is no evidence for substantial tectonic uplift in the Piedmont during the Late Oligocene and the rejuvenation of the Piedmont appears to have occurred suddenly and with relatively rapid uplift at the beginning of the Miocene.
A linear depression (or series of depressions) formed within the Gulf Trough during the Oligocene (Fig. 48, Pl.2). The depression (or depressions) appears to have developed on the top of the Oligocene and is filled with gray to dark gray, fine- to medium-grained sand and clay that is barren of carbonates and is thought to be of earliest Miocene age (Parachucla Formation). The depression (or depressions) extends from eastern Irwin County southwestward to Mitchell County and ranges from 100 feet (30m) to almost 300 feet (91 m) thick. It has the appearance of a narrow river valley within the Gulf Trough but it cannot yet be traced southwest of Mitchell County or northeast of Irwin County. Because the inner part of the Chattahoochee Embayment southwest of Mitchell County appears to have been emergent during the Late Oligocene, I think that if the depression were a rivervalley,it wouldextendintoFlorida. Becauseit does not, I suggest that the linear depression is either of karst origin or is related to differential sedimentation within the Gulf Trough during the Vicksburgian. If this model

142

is accurate, it seems likely that the depression(s) would Miocene. In the eastern Gulf Coastal Plain, however, the

havebeenlacustrineduringtheLateOligocenelowstands evolving Oligocene environment of deposition does not

of the sea butreceived no siliciclastics from the surround- appear to be transitional to the Miocene but appears to be

ing karst terrane. The initial sand and clay fill of the mainly offlap of the Eocene with a number of pulses of

depressions would then represent the oldest sediments siliciclastic deposition (Forest Hill-Red Bluff, Byram, and

eroded from the rising Piedmont at the'verybeginning of Bucatunna).

the Miocene.

When the sea again reentered the Gulf Trough

MIOCENFJOLIGOCENE BOUNDARY

near the beginning of the Miocene, the southwestern part

of the Gulf Trough in the Chattahoochee Embayment in

Southeastern North America is a poor place to

Florida remained in very shallow, brackish water, whereas study the Oligoc~ne/Miocene boundary. The Upper

the northeastern part of the trough was in somewhat Oligocene is poorly represented in the region, with the

deeper water under inner continental shelf conditions. only deposits of known Late Oligocene age being as-

The marine influences in the Gulf Trough in Georgia signed to the Chickasawhayan. However, the precise

duringthe Miocene werederived from the AtlanticOcean correlation of the Chickasawhayan with the standard

rather than the Gulf of Mexico.

planktonic microfossil zonations has yet to be accom-

plished. In terms of planktonic foraminiferal zonation,

ENVIRONMENTAL EVOLUTION DURING THE the best approximation at this time is correlation with the

OLIGOCENE

Globorotalia opima opima Zone. Because the

Chickasawhayan in Mississippi and Alabama represents

The environmental evolution of the onshore Oli- mainly an inner neritic, continental shelf environment,

gocene, and especially that of the eastern Gulf Coastal the Chickasawhayan deposits do not contain rich plank-

Plain, appears to be different from that of the outer tonic foraminiferal suites and Globorotalia opima is repre-

continental shelf of Georgia. In the eastern Gulf Coastal sented by small to large G. opima nana (also see Poag, 1966,

Plain, the Oligocene can be characterized by a progres- 1968?).

sivewestwardexpansionoftheofthecarbonatelithosome.

In the Ashley Member of the Cooper Formation

ThemiddleVicksburgian, limestone (GlendonLimestone) in South Carolina which represents an outer neritic, con-

was being deposited at Vicksburg on the Mississippi tinental shelf environment, and in the Cooper under the

River. Only subsequent to the deposition of the Glendon outer continental shelf of Georgia, the Chickasawhayan

was there a progressive shallowing of the shelf and a planktonic foraminiferal suite is still not diverse and

seaward (southward) and eastward expansion of the Globorotalia opima nana is poorly represented. The consis-

siliciclastic lithosome. The greatest expansion of the tent presence of Globigerina angulisuturalis, however, in

Oligocenesiliciclasticlithosomeoccurredduringthedepo- Chickasawhayan deposits across the southeast indicates

sition of the Bucatunna Clay. Subsequently, during the that the ChickasaWhayan is post-Globigerina ampliapertura

Chickasawhayan, the shelf deposits westward into Mis- Zone.

sissippi were a mixture of carbonates and siliciclastics.

The significant evolutionary advancementin the

On the outer continental shelf and perhaps on- planktonic foraminiferal suite of the basal Miocene,

shore in eastern Georgia, another sort of environmental Aquitanian, lower Parachucla Formation in Georgia

evolution appears to have occurred. The Upper Eocene (Huddlestun, 1988) over that of the Chickasawhayan

carbonates onshore and offshore are devoid ofphosphate and any significant amounts of siliciclastics except in the coastal environment (Barnwell Group). However, the Vicksburgian is characterized by the sudden appearance but minor occurrence ofboth phosphate and siliciclastics. The amount of phosphate and siliciclastics appear to increase incrementally from the early Vicksburgian through the subsequent Chickasawhayan, and into the lower Aquitanian.
The above observations are interpreted as indicating differing evolving conditions in the Gulf Coastal Plain .and the Atlantic Coastal Plain. The beginning of phosphate generation in the Atlantic Coastal Plain began near the beginning of the Oligocene and increased incrementally through the Oligocene. In that area, the Oligocene can be viewed as transitional from the Eocene to the

suggests a significant time gap between the Chickasawhayan and the Aquitanian. Based on the relative changes in the planktonic foraminiferal faunas, the Chickasawhayan/Aquitanian hiatus would appear to be greater than that of the Vicksburgian/Chickasawhayan hiatus.
In most areas in Mississippi, Alabama, Florida, and Georgia, the Chickasawhayanis not directlyoverlain by the Aquitanian. Where it may be (Mississippi and Alabama), the Aquitanian is nonfossiliferous in terms of calcareous fossils. In the panhandle of Florida, the Chickasawhayanis commonlyoverlainby the Aquitanian Chattahoochee Formation or by the upper Burdigalian (upper Lower Miocene)(Huddlestun, 1984). In Georgia, and much of peninsular Florida, the Aquitanian directly overlies upper Vicksburgian, Byram- or Bucatunnaequivalent deposits. On the outer continental shelf of

143

Georgia,boththeChickasawhayanand lowerAquitanian contain unusually sparse planktonic foraminiferal faunas, Perhaps the best area to study the nature of the Oligocene/Mioceneboundaryin outcrop or shallow cores in the southeastern United States is in the Cooper Formation in the vicinity of Charleston, South Carolina. In that area, middle to outer neritic Aquitanian (Cooper Formation) directly overlies middle to outer neritic Chickasawhayan (Ashley Member of the Cooper Formation). Sediments of latest Oligocene age may be present in that area. It is also possible that there is a more extended UpperOligoceneand LowerMiocene sectionin the subsurface of southern Florida.
REFERENCES CITED
Adey, W. H., and Macintyre, I. G., 1973, Crustose coral-
line algae: a re-evaluation in the geological sciences: Geol, Soc. Amer. Bull., v. 84, p. 883-904.
A,merican Association of Petroleum Geologists, 1975, Geologkal highway map of the southeastern region: Amer. Assoc. Pet. Geol. Map no. 9, scale, 1 inch to approximately 30 miles, Tulsa, Okla.
American Conunission on Stratigraphic Nomenclature, 1961, Code of Stratigraphic Nomenclature: Am. Assoc. Pet. Geol. Bull., v. 45, no. 5, p. 645-665.
_ __, 1970, Code of Stratigraphic Nomenclature (2nd printing): Am. Assoc. Pet. Geol., Tulsa, Okla, 22
P
Andress, N. E., Cramer, F. H., and Goldstein, R. F., 1969, Ordovician chitinozoans from Florida well samples: Trans., Gulf Coast Assoc. Geol. Soc., v. 19, p. 369-375.
Applin, E. R., 1960, A tropical sea in central Georgia in Late Oligocene time: U. S. Geol. Survey Prof. Paper 4(){)-B, p. B207-B209.

stratigraphy and structure of Florida and southem Georgia: Am. Assoc. Pet. Geol. Bull., v. 28, no. 12, p. 1673-1753.
_ __, 1965, The Comanche Series and associated rocks in the subsurfacein central and south Florida:U.S. Geol. Survey Prof. Paper 447, 84 p.
_ __, 1967, The Gulf Series in the subsurface in northem Florida and southern Georgia: U. S. Geol. Survey Prof. Paper 524-G, 35 p.
Arden, D. D., Jr., 1974, A geophysical profile in the Su-
wannee Basin, Northwestern Florida, in Sympo-
sium on the petroleum geology of the Georgia Coastal Plain: Georgia Geol. Survey Bull. 87, p. 111-122.
Babcock,C.1969,GeologyoftheUpperCretaceousclastic section northern peninsular Florida: Florida Geol. Survey Inf. Circ. 60, 44 p.
Bandy, 0. L., 1949, Eocene and Oligocene foraminifera
from Little Stave Creek, Clarke County, Alabama: Bull. Amer. Pal., v. 32, no. 131, 210 p ..
Banks, J., 1976a, Tectonics of central Florida: in Mid-
Tertiary carbonates Citrus, Levy, Marion Counties west central Florida:Southeastem Geol. Soc. Field trip guidebook 18, p. 17-35.
__, 1976b, Middle Tertiary lithostratigraphic units in
the geologic column of central Florida: in Mid-
Tertiary carbonate~ Citrus, Levy, Marion Counties west central Florida: Southeastern Geol. Soc. Field trip guidebook 18, p. 63-65.
Barnett, R. S., 1975, Basement structure of Florida and its tectonic implications: Trans., Gulf Coast Assoc. Geol. Soc.:~ v. 25, p. 122-142.

Applin, E. R., and Applin, P. L., 1964, Logs of selected wells in the Coastal Plains of Georgia: Georgia Geol. Survey Bull. 74, 229 p.
Applin, E.R., and Jordan, L., 1945, Diagnostic foraminifera from subsurface formations in Florida: Jour. Pal., v. 19, no. 2, p. 129-148.

Baum, G. R., and Vail, P.R., 1988, Sequence stratigraphic concepts applied to Paleogene outcrops, Gulf
and Atlantic basins, in Wigus, C.K., Hastings, B.
S., Kendall, C.G.St.C, Posamentier, H.W., Ross, C. A., and Van Wagoner, J. C., (eds.), Sea-level changes: An integrated approach: Soc. Econ. Pal. and Min. Spec. Publ., no. 42, p. 309-327.

Applin, P. L., 1951, Preliminary report on buried preMesozoic rocks in Florida and adjacent states: U.S. Geol. Survey Circ. 91, 28 p.
Applin, P. L., and Applin, E. R., 1944, Regional subsurface

Blow, W. H., 1969, Late middle Eocene to Recent planktonic foraminiferal biostratigraphy,in Broniman, P., and Renz, H.H., (eds.), Proc., First Int. Conf. Planktonic microfossils, Geneva,1967: E. J. Brill, Leiden, Holland, p. 199-421.

144

Bolli, H. M., 1957, Planktonic foraminifera from the Oligocene- Miocene Cipero and Lengua Formations of Trinidad, B.W.I.: U. S. Nat. Mus. Bull. 215, p. 97-123.
Bosellini,A.,andGinsburg,R.N., 1971,Formandintemal structureofRecentalgal nodules (rhodolites)from Bermuda: Jour. Geol., v. 79, p. ~2.
Bowman,J.K.,andManker,J.P., 1982,Smectite-richclays associated with an Oligocene algal reef (abst.): Georgia Jour. Sci., v. 40, p. 20.
Brantley, J. E., 1916, A report on the limestones and marls of the Coastal Plain of Georgia: Georgia Geol. Survey Bull. 21,300 p.
Bryan, J. R. 1991, Stratigraphic and paleontological studies of Paleocene and Oligocene carbonate facies of the eastern Gulf Coastal Plain: Unpubl. Ph.D. Dissertation, University of Tennessee, Knoxville, 324 p.
Bryan, J. R. and Huddlestun, P. F., 1990, Correlation and
age of the Bridgeboro Limestone- a coralgallimstone from southwestern Georgia (abst.): Geol. Soc. Amer., Abstracts with Programs, v. 22, no. 4, p.4.
Callahan, J. T., 1964, The yield of sedimentary aquifers of the Coastal Plain southeast river basins: U. S. Geol. Survey Water-Supply Paper 1669-W, 59 p.

al implications: U. s~ Geol. Survey Prof. Paper 1313-L, p. Ll-L42.
Cole, W. S., 1934, Oligocene orbitoids from near Duncan Church,Washington County, Florida: Jour. Pal., v. 8, no. 1, p. 21-28.
~ 1941, Stratigraphic and paleontologic studies of wells in Florida: Florida Geol. Survey Bull. 19,
89 p., (Dictyoconus - p. 13-14).
Cole, W. S., and Applin, E. R., 1964, Problems of the geographic and stratigraphic distribution of American Middle Eocene larger foraminifera: Bull. Amer. Pal., v. 47, no. 212, 48 p.
Cole, W. S., and Ponton, G. M., 193_0, The foraminifera of the Marianna Limestone of Florida: Florida Geol. Survey Bull. 5, p. 19-69.
Coleman, J., and Galloway, W. E., Sequence stratigraphic analyses of the lower Vicksburg Formation of
Texas, in Armentraut, J.M., and Perkins, B. F.,
(eds.), Sequence stratigraphy as an exploration tool Concepts and practices in the Gulf Coast: Gulf Coast Sec. Soc. Econ. Pal. and Min. Foundation, Eleventh Ann. Res. Conf., p. 99-112.
Conrad, T. A., 1848a, Observations on the Eocene formation, and descriptions of one hundred and five new fossils of that period, from the vicinity of Vicksburg, Mississippi, withanAppendix: Acad. Nat. Sci. Philadelphia, Proc.1847, v.3, p.280-299.

Carter, B. D., 1987, Paleogene echinoid distributions in the Atlantic and Gulf Coastal Plain: Palaios, v. 2, p. 390-404.
__, 1990, Late Eocene echinoid biofacies of Florida: Palaios, v. 5, p. 176-183.
Carter, B. D. and Manker,J. P., 1987,Is the PelhamEscarpment purely an erosional feature: Georgia Jour. Sci. v. 'p. 110.
Cheetham, A. H., 1963, Late Eocene zoogeography of the eastern Gulf Coast region: Geol. Soc. Amer., Mem. 91, 113 p.
Chen, C. S., 1965, The regional lithostratigraphic analysis ofPaleocene and Eocene rocks of Florida: Florida Geol. Survey Bull. 45, 105 p.

__, 1848b, Observations on the Eocene formation, and descriptions of one hundred and five new fossils of that period, from the vicinity of Vicksburg, Mississippi, with an Appendix: Acad. Nat. Sci. Philadelphia, Jour., 2nd ser., v.1, pt.2, p.111-134.
Cook, F. A., Albaugh, D. S., Brown, L. D., Kaufman, S., Oliver,J. E.,andHatcher,R. D., 1979, Thin-skinned tectonics in the crystalline S. Appalachians: COCORP seismic-reflection profiling of theBlue Ridge and Piedmont: Geology v. 7, p. 563-567.
Cooke, C. W., 1918,CorrelationofdepositsofJacksonand Vicksburg ages in Mississippi anAlabama:Washington Acad. Sci. Jour., v. 8, p. 186-198.
__, 1923, The correlationof the Vicksburg Group: U. S. Geol. Survey Prof. Paper 133, p. 1-9.

Chowns, T. M., and Williams, C. T., 1983, Pre-Cretaceous __, 1926, Geology of Alabama; the Cenozoic forma-

rocks beneath the Georgia Coastal Plain-region-

tions: Alabama Geol. Survey Spec. Rept. 14, p.

145

251-297.
---' 1935,Noteson theVicksburgGroup: Amer. Assoc. Pet. Geol. Bull., v. 19, p. 1162-1172.
- - - ' 1936, Geology of the Coastal Plain of South Carolina: U. S. Geol. Survey Bull. 867, 196 p.

- - - ' 1929, Notes on the foraminifera of the Byram Marl: Cushman Lab. Foram. Research Contr., v. 5, p. 40-48. .
- - - ' 1935, New species of foraminifera from the lower Oligocene of Mississippi: Cushman Lab. Foram. Research Contr., v. 11, p. 25-37.

- - - ' 1939, Geologic map of Georgia; Coastal Plain: Georgia Geol. Survey, Atlanta, 1:500,000.
___..J 1942,CenozoicirregularechinoidsofeasternUnited States: Jour. Pal. v. 16, no. 1, p. 1-62.
- - - ' 1943, Geology of the Coastal Plain of Georgia: U. S. Geol. Survey Bull. 941,121 p.
- - - ' 1945, Geology of Florida: Florida Geol. Survey Bull. 29,339 p.
- - - ' 1959, Cenozoic echinoids of eastern United States: U. S. Geol. Survey Prof. Paper 321, 106 p.

Cushman,J.A.,andMcGlamery, W.,1938,0ligoceneforaminifera. from Choctaw Bluff, Alabama: U.S. Geol. Survey Prof. Paper 189-D, p. D103-D119.
- - - ' 1939, New species of foraminifera from the lower Oligocene of Alabama: Cushman Lab. Foram. Research Contr., v. 15, p. 45-49.
- - - ' 1942,Oligocene foraminifera near Milry, Alabama: U.S. Geol. Survey Prof. Paper 197-B, p. 65-84.
Cushman, J. A., and Todd, R., 1946, A foraminiferal fauna from theByrammarl atitstype locality: Cushman Lab. Foram. Research Contr., v. 24, p. 76-102.

Cooke, C. W., and Mansfield, W. C., 1936, Suwannee - - - ' 1948, Foraminifera from the Red Bluff-Yazoo sec-

Limestone of Florida (abst.): Geoi. Soc. Amer.

tion at Red Bluff, Mississippi: Cushman Lab.

Proc. for 1935, p. 71-72.

Foram. Research Contr., v. 24, p. 1-12.

Cooke, C. W., and Mossom, S., 1929, Geology of Florida: Florida Geol. Survey,20th Ann. Rept., p. 29-227.
Cramer, F. H., 1971, Position of the north Florida lower Paleozoic block in Silurian time- Phytoplankton evidence: Jour. Geophys. Res., v. 76, p. 47544757.

Dall, W. H., 1892, Florida, in Dall, W. H., and Harris, G.
D., Correlation papers Neocene: U. S. Geol. Survey Bull. 84, p. 85-158.
- - - ' 1916, A co~tribution to the invertebrate fauna of the Oligocene beds of Flint River, Georgia: U. S. Nat. Mus. Proc., v. 51, p. 487-524.

- - - ' 1973, Middle and Upper Silurian chitinozoan succession in Florida subsurface: Jour. Pal., v. 47, p. 279-288.
Cramer, H. R., and Arden, D. D., 1980, Subsurface Cretaceous and Paleogene geologyofthe Coastal Plain ofGeorgia: Georgia Geol. Survey, Open-fileRept. 80-8,184 p.

Dall, W. H., and Harris, G. D., 1892, Correlation papers Neocene: U. S. Geol. Survey Bull. 84, 349 p.
Dallmeyer, R. D., 1987,40Ar;39Ar age of detrital muscovite within Lower Ordovician sandstone in the Coastal Plain basement of Florida: Implications for west African terrane linkages: Geology, v.15, p. 998-1001.

Cushman, J. A., 1922a, The Byram calcareous marl ofMississippi and its foraminifera: U.S. Geol. Survey Prof. Paper 129-E, p. 79-122.
- - - ' 1922b, The foraminifera of the Mint Spring calcareous marl member of the Marianna.Limestone: U. S. Geol. Survey Prof. Paper 129-F, p. 123-152.
- - - ' 1923, The foraminifera of the Vicksburg Group: U. S. Geol. Survey Prof. Paper 133, p. 11-71.

Daniels, D. L.,Zietz, I, and Popenoe, P., 1983, Distribution of subsurface lower Mesozoic rocks in the South eastern United States, as interpreted from regional aeromagnetic and gravity maps: U. S. Geol. Survey Prof Paper, 1313K, p: Kl-K24.
DeBoo,P. B., 1965, Biostratigraphiccorrelationofthetype Shubuta Member of the Yazoo Clay and Red Bluff Clay with their equivalents in southwestem Alabama: Alabama Geol. Survey Bull. 80, 84 p.

146

Dockery, D. T.,III, 1982, LowerOligoceneBivalviaofthe Vicksburg Group in Mississippi: Mississippi Geol. Survey Bull. 123,261 p.
____J 1988, The influence of the ancient Gulf Stream on Paleocene molluscan provinces in the northern Gulf and Atlantic Coastal Plain (abst.): Geol. Soc. Am., Abstracts with Programs, v. 20. no. 4, p. 261.
____J 1990, The Eocene-Oligocene boundary in the
northern Gulf- a sequence boundary, in Armen-
trout, J.M, and Perkins, B.F., (eds.), Sequence stratigraphy as an exploration tool, Concepts and practices in the Gulf Coast: Gulf Coast Sec. Soc. Econ. Pal. and Min. Foundation, Eleventh Ann. Res. Conf., p. 141-150.

v. 47, p. 149-160.
Glawe, LN., 1974,UpperEoceneandOligocenePectinidae of Georgia and their stratigraphic significance: Georgia Geol. Survey Inf. Circ. 46, 27 p.
Gohn, G. S., Gottfried, D., Lanphere, M.A., and Higgins, B. B., 1978, Regional implications of Triassic or Jurassic age for basaltandsedimentaryredbeds in the South Carolina Coastal Plain: Science, v. 202, no. 4370, p. 887-890.
Goldstein, R. F., Cramer, F. H., and Andress, N. E., 1969, Silurianchitinozoans from Florida well samples: Trans.,GulfCoastAssoc.Geol. Soc., v.19, p.377384.

Fisher, R., and Ward, K., 1984, Paleoenvironmental re- Gray, M.G., 1978, Pre-Gulfian rocks of the southwestern

constructionof the Vicksburg Group (Oligoene),

Georgia Coastal Plain: Unpubl. M. S. Thesis,

Warren County, Mississippi: Mississippi

Emory University, Atlanta, Georgia, 72 p.

Geol., v. 4, no. 3, p. 1-9.

Haq, B. U., Hardenbol, J., and Vail, P.R., 1987, Chronol-

Foley, F. D., 1981, Neogene seismic stratigraphy and de-

ogy of fluctuating sea levels since the Triassic:

positiona! historyof the lower Georgia coast and

Science, v. 2235, p. 1156-1167.

continental shelf: Unpubl. M.S. Thesis, Unversi-

ty of Georgia, Athens, 80 p.

Hardenbol, J., and Berggren, W. A., 1978, A new Paleo-

gene numerical time scale, in Cohee, G. V.,

Folk, R. L., and Sneed, E. D., 1958, Petrology of sedimen-

Glaessner, M. F., and Hedberg, H. D., (eds.),

tary rocks: Austin, Tex., Hemphill Publ. Co., 170

Contributions to the geologic time scale: Amer.

p.

Assoc. Pet. Geol., no. 6, p. 213-234.

Forston, C. W., Jr., and Navarre, A. T., 1959, Limestones exposed in the lower Withlacoochee valley of Georgia: Southeastern Geol., v. 1, p. 73-76.
Furlow, J. W., 1969, Stratigraphy and economic geology of the eastern Chatham County phosphate deposits: Georgia Geol. Survey Bull. 82, 40 p.

Hathaway,J.C.,Schlee,J.S.,Poag,C. W., Valentine,P.C., Weed, E. G. A., Bothner, M. H., Kohout, F. A., Manheim, F. T., Schoen, R., Miller, R. E., .and Schultz, D. M., 1976, Preliminary summary of the 1976 Atlantic margin Coring Project of the U.S. Geol. Survey: U. S. Geol. Survey Open-file rept. no. 76-844, 217 p.

Gelbaum, C. S., 1978, The geology and ground water of
the Gulf Trough, in Short contributions to the
geology of Georgia: Georgia Geol Survey Bull. 93, p. 38-49.

Hazel,J.E.,Mumma,M.D.,andHuff,W.J., 1980,0stracode biostratigraphy of the Lower Oligocene (Vicksburgian) of Mississippi and Alabama: Trans., Gulf Coast Assoc. Geol. Soc., v. 30, p. 361-401.

Gelbaum, C. S., and Howell, J. E., 1982, The geohydrology
of the Gulf Trough, in Arden, D. D., Beck, B. F.,
and Morrow, E., (eds.), Second symposium on the geology of the southeastern Coastal Plain: Georgia Geol. Survey Inf. Circ. 53, p. 140-153.
Georgia Geological Survey, 1976, Geologic map of Georgia: Atlanta,GeorgiaGeologicSurvey, 1:500,000.

Heller, J. A., and Bryan, J. R., 1992, First Oligocene occur
renee of the irregular echinoid Macropneustes mortoni (Conrad): Jour. Paleont. v 66, no. 2, p.
345-346.
Hendry, C. W., and Sproul, C. R., 199(5, Geology and ground-water resources of Leon County, Florida: Florida Geol. Survey Bull. 47,178 p.

Gladfelter, W. B., 1978, General ecology ofthe cassiduloid Hendy, W. J., 1948, Notes on the stratigraphy of

urchin Cassidulus caribbearum: Marine Biology,

northeastern Wayne County, Mississippi:

147

in Mississipppi Geol. Soc., sixth Field trip
guide book, p. 25-31.

Georgia: Georgia Geol. Soc., 14th Field trip guide book, Georgia Geol. Survey, Atlanta, 89 p.

Heron, S.D., Jr.1 and Johhson, H. S., Jr.,1966, Clay mineralogy, stratigraphy, and structural setting of the Hawthorn Formation, Coosawhatchie district: Southeastern Geol., v. 7, no. 2, p. 51-63.

Huddlestun, P. F., and Toulmin, L. D., Jr., 1965, Upper Eocene-Lower Oligocene stratigraphy and paleontology in Alabama: Trans., Gulf Coast Assoc. Geol. Soc., v. 15, p. 155-159.

Hetrick, S. M., 1961, Well logs of the Coastal Plain of Georgia: Georgia Geol. Survey Bull. 70, 462 p.
Herrick, S. M., and Counts, H. B., 1968, Late Tertiary stratigraphy of eastern Georgia: Georgia Geol.Soc., 3rd Field trip guidebook, 88 p.
Herrick, S.M., and Vorhis, R. C., 1963, Subsurface geology of the Georgia Coastal Plain: Georgia Geol. Survey lnf. Circ. 25,78 p.
s. . Hetrick1J. H.,Friddell,M. and Weaver, C. E.,1987.. Clay
mineralogy of the Hawthorne Group: Georgia GeoL Survey Irtf. Circ. 79,47 p.

Huddlestun, P. F., Braunstein, J., and Biel, R., 1988, Correlationof stratigraphic units in North AmericaGulfCoastregioncorrelationchart; Amer.Assoc. Pet. Geol., Tulsa, Oklahoma.
Huddlestun, P. F., Hetrick, J. H., and Kellam, M. F.,
1992, The geologic history of the Georgia Channel System in Georgia: Georgia GeoL Survey, in manuscript, 415 p.
Huddlestun, P. F., Marsalis, W. E., and Pickering, S. M., 1974, Tertiary stratigraphy of the central Georgia Coastal Plain: Guidebook 12, Southeastern Sec., Geol. Soc. Amer., 35 p.

Horowitz, C. G., 1979, Benthic foraminifera of the Oligocene Suwannee Limestone, Georgia and northem Florida: Unpubl. M.S. Thesis, University of Georgia, Athens, 160 p.

Buddlestun, P. F.~Jluntet, M. E., and Carter, B. D., 1988, The Suwannee Strait as a faunal province bound ary (abst.): Geol. Soc. Am. Abstracts with Programs, v. 20, no. 4, p. 271.

Huddlestun, P. F. 1965, Correlation of Upper Eocene and Lower Oligocene strata between the Conecuh, Sepulga, and Choctawhatchee Rivers of southem Alabama: Unpubl. M.S. Thesis, Florida State University, Tallahassee, 101 p.
~ 1966, Facies change within Upper Eocene-basal
Oligocene deposits in Alabama, in Guidebook for the 4th Ann. Field trip of the Alabama Geol.
Soc., p. 41-42.
_____._, 1981, Correlation chart, Georgia Coastal Plain: Georgia Geol. Survey Open-file Rept. 82-1.
______J 1984, The Neogene stratigraphy of the central Florida panhandle: Unpubl. Ph.D. Dissertation, Florida State University; Tallahassee, 210 p.
______J 1988, A revision of the lithostratigraphic units of the CoastalPlainofGeorgia,the Miocenethrough Holocene: Georgia Geol. Survey Bull. 104, 162 p.
Huddlestun_. P. F., and Hetrick, J.H., 1978, Stratigraphy of the Tobacco Road Sand- a new formation: Georgia Geol. Survey Bull. 93, p. 56-77.
_____J 1979, The stratigraphy of the Barnwell Group of

Hull, P. 0., 1962, Cretaceous Suwannee Strait, Georgia
and Florida: Amer. Assoc. Pet. Geol. Bull., v. 46, p. 118-122.
Hunter; M. E., 1972, Biostratigraphy and paleontology,
in Oligocene stratigraphy- a study of Lansing
Quarry near Brooksville, Hernando County,
Florida: Bay Area Geol. soc. . First field conf., 32
p.
_____._, 1976, Biostratigraphy: in Mid-Tertiary carbonates
Citrus, Levy, MarionCounties west central Florida: Southeastern GeoL Soc. Field trip guidebook 18, p. 6687.
Ingram, R. L., 1954, Terminology for the thickness of stratification and parting units in sedimentary rocks: Geol. Soc. Amer. Bull., v. 65, p. 937-938.
International Subcommission on Stratigraphic Classification; 1976, International stratigraphic guide: (Hedberg, H. D., Ed.), John WileyandSons,New Yotk, 200p.
Kauffman, E. G., 1969, Form, function, and evolution: in Moore, R. C., (Ed.), Treatise on Invertebrate Paleontology, Mollusca, BivalVia: Geol. Soc. Amer.

148

and University of Kansas, Lawrence,PartN, v.1, p. N129-N205.

the Vicksburg Group in Mississippi: Mississippi Geol. Survey Bull. 124,415 p.

Kier, P. M., 1962, Revision of the cassiduloid echinoids: Maher, J. C., 1965, Correlation of subsurface Mesozoic

Smithsonian Miscellaneous Collections, v. 144,

and Cenozoic rocks along the Atlnatic coast:

262p.

Amer. Assoc. Pet. Geol., Tulsa, 16, p. 9 pis.

-----J 1975, The echinoids of Carrier Bow Cay, Belize: Smithsonian Contr. Zoology, v. 206, 45 p.
-----J 1984, Fossil spatangoid echinoids of Cuba: Smithsonian Contr. Paleobiology, v. 55, 336 p.
Kier, P.M., and Grant, R. E., 1965, Echinoid distribution and habits, Key Largo Coral Reef Preserve, Florida: Smithsonian Miscellaneous Collections, v. 149,68 p.
Klitgord, K. D., Popenoe, P., and Schouten, H., 1984, Florida: a Jurassic trasnform plate boundary: Jour. Geophysical Res., v.89,no. B9, p. 7753-7772.
Klitgord, K. D., Dillon, W. P., and Popenoe, P., 1983, Mesozoic tectonics of the Southeastern United States Coastal Plain and continental margin: U. S. Geol. Survey Prof. Paper 1313-P, p. P1-P15.
Kohn, A. J., 1959, The ecology of Conus in Hawaii: Ecological Monographs, v. 29, p. 47-90.

-----J 1971, Geologic framework and petroleum potential of the Atlantic Coast Plain and continental shelf: U.S. Geol. Survey Prof. Paper, 659, 98 p.
Mancini, E. A., and Tew, B. H., 1990, Relationships of Paleogene stageboundaries to group and unconformity-bound depositional sequence contacts in Alabama and Mississippi, in Armentrout, J.M., and Perkins, B.F., (eds.), Sequence stratigraphy as an exploration tool, Concepts and practices in the Gulf Coast: Gulf Coast Sec. Soc. Econ. Pal. and Min. Foundation, Eleventh Ann. Res. Conf., p. 221-228.
Manker, J. P., and Carter, B. D., 1987, Paleoecology and paleogeography of an extensive rhodolith facies from the Lower Oligocene of south Georgia and north Florida: Palaios, v. 2, p. 181-188.
Mansfield, W. C., 1937, Mollusks of the Tampa and Suwannee Limestones of Florida: Florida Geol. Survey Bull. 15,334 p.

MacNeil, F. S., 1944a, The Coastal Plain of Georgia, in Southwestern Georgia Field trip: Southeastern Geol. Soc., 2nd Field trip guidebook, p. 3-5.
-----J 1944b, The Tertiary formations: in Southwestern GeorgiaField Trip: Southeastern Geol. Soc., 2nd Field trip guidebook, p. 35-37.

-----J 1938, Oligoc.ene faunas from the lower and upper beds on the A. L. Parrish farm, Washington County, Florida: Washington Acad. Sci. Jour., v. 28, no. 3, 93-107.
-----J 1940, Mollusks of the Chickasawhay Marl: Jour. Pal., v. 14, no. 3, p. 171-225.

-----J 1944c, Oligocene stratigraphy of southeastern United States: Amer. Assoc. Pet. Geol. Bull., v. 28, no. 9, p. 1313-1354.
-----J 1946, The Tertiary formations of Alabama: Fourth field trip, Southeastern Geol. Soc., 91 p.
-----J 1947a, Correlation chart for the outcropping Tertiary formations of the eastern Gulf region: U.S. Geol. Survey Oil and Gas Inv., Prelim. Chart 29.
-----J 1947b, Geologic map of the Tertiary and Quaternary formations of Georgia: U. S. Geol. Survey Oil and Gas Inv. Prelim. Map 72.

Matson, G. C., and Clapp, F. G., 1909, A preliminary report on the geology of Florida with special reference to the stratigraphy: Florida Geol. Survey Second Ann. Rept., p. 21-173.
McFadden, S. S., Hetrick, J. H., Kellam, M. F., Rodenbeck, S. A., and Huddlestun, P. F., 1986, Geologic data of the Gulf Trough area, Georgia: Georgia Geol. Survey Inf. Circ. 56, 345 p.
McKinney, M. L., 1984, Suwannee Channel of the Paleogene Coastal Plain: Support for the "carbonate suppression" model of basin formation: Geology, v. 12, no. 6, p. 343-345.

MacNeil,F.S.,and Dockery, D. T.,1984,Lower0ligocene Miller,J. A., 1982,'Geology and configuration of the top

Gastropods, Scaphopoda, and Cephalapoda of

of the Tertiary Limestone Aquifer System,

149

southeasterneastern United States: U. S. Geol. Survey WaterResources Investigations 81-1178, 1:1,000,000.

geochronolgic investigation of lower Paleozoic rocks from thesubsurfaceofFlorida: Geology, v. 15, p. 900-903.

_ , 1986, Hydrologic framework of the Florida Aquifer System in Florida and in parts of Georgia, Alabama and South Carolina: U.S. Geol. Survey Prof. Paper 1403-B, 91 p.
Moore, W. E., 1955, Geology of Jackson County, Florida: Florida Geol. Survey Bull. 37,101 p.
Mortensen, T. H., 1948a, A monograph of the Echinoidea, V. N, Part 1, Holectypoida and Cassiduloida: Copenhagen, C.A., Reitzel, 363 p.

Owen, V., 1963, Geology and ground-water resources of Mitchell County, Georgia: Georgia Geol. Survey Inf. Circ. 24, 40 p.
Owens, H., 1960,Florida-Bahama Platform(abst.): Amer. Assoc. Pet. Geol. Bull., v. 44, p. 1254.
Palmer, K. V. W., 1953, part 2.-Gastropoda, p. 9-11, in
Richards, H. G., and Palmer, K. V. W., Eocene mollusksfrom Citrusand LevyCounties,Florida: Florida Geol. Survey Bull. 35, 67 p.

_ , 1948b, Amonographofthe Echinoidea, v. 14, pt. 2, Patterson, S. H., and Herrick, S.M., 1971, Chattahoochee

Clypeasteroida: Copenhagen, C.A. Reitzel, 471

Anticline, Apalachicola Embayment,GulfTrough

p., 72 pls.

and related structural features, southwestern

Georgia, fact or fiction: Georgia Geol. Survey Inf.

Mossom, D. S., 1925, A preliminary report on the lime-

Circ. 41, 16 p.

stones and marls of Florida: Florida Geol. Sur-

vey Ann. Rept. 16, p. 27-203.

PennWell Publishing Co., 1982, Oil and Gas Fields of the

United States: PennWell Publ. Co., Tulsa, Okla-

Mueller, P. A., and Porch, J., 1983, Tectonic implications

homa.

of Paleozoic and Mesozoic igneous rocks in the

subsurface of peninsular Florida: Trans., Gulf Pickering,S.M.,Jr.,1970,Stratigraphy,paleontology,and

Coast Assoc. Geol. Soc., v. 33, p. 169-173.

economic geologyofportions ofPerry andCoch-

ran quadrangles, Georgia: Georgia Geol. Sur-

Murray, G. E., 1961, Geology of the Atlantic and Gulf

vey Bull. 81, 67 p.

Coastal Province of North America: Harper and

Bros., New York, 692 p.

_ , 1974, An apparent domal structure in Wayne

County, Georgia, in Stafford, L. P., (ed.), Sympo-

Nelson, K. D., Arnow, J. A., McBridem, J. H., Willemin, J.

sium on the petroleum geology of the Georgia

H., Haung, J., Zheng, L., Oliver, J. E., Brown, L.

Coastal Plain: Georgia Geol. Survey Bull. 87, p.

D., and Kaufman, S., 1985a, New COCORP pro-

189-191.

filing in theSE U.S. part 1: Late Paleozoic suture

and Mesozoic rift basin: Geology, v. 13, p. 741- Pinet, P.R., and ~openoe, P., 1985, A scenario of Meso-

718,

zoic-Cenozoic ocean circulation over the Blake

Plateau and its environs: Geol. Soc. Amer. Bull.,

Nelson, K.D., McBride, J.H., Arnow, J.A., Oliver, J.E.,

v. 96, p. 618-626.

Brown, L. D., and Kaufman, S., 1985b, New

COCORP profiling in the southeastern United Poag, C. W., 1966, Paynes Hammock (Lower Miocene?)

States, Part II: Brunswick and east coast magnetic

foraminifera of Alabama and Mississippi: Mi-

anomalies opening of the north-central Atlantic

. cropaleontology, v. 12, no. 4, p. 393-440.

Ocean: Geology, v. 13, p. 718-721.

_ ,1972,PlanktonicforaminiferaoftheChickasawhay

North American Commission on Stratigraphic Nomen-

Formation, United States Gulf Coast: Micropal-

clature, 1983, North American Stratigraphic

eontology, v. 18, no. 3, p. 257-277.

Code: Amer. Assoc. Pet. Geol. Bull., v. 67, no.

5, p. 841-875.

Fojeta, J., Jr., Kriz, J., and Berdan, J. M., 1976, Silurian-

Devonian pelecypods and Paleozoic stratigra-

Opdyke, N.D., Jones, D. S., MacFadden, B. J., Smith, D.

phy of subsurface rocks in Florida and <;;eorgia

L., Mueller, P. A., and Shuster, R. D., 1987,

and related Silurian pelecypods from Boliviaand

Florida as an exotic terrane Paleomagnetic and

Turkey: U.S. Geol. Survey Prof. Paper879, 32 p.

150

Popenoe, P., 1977, A probable major Mesozoic rift system inSouth Carolina and Georgia (abs.): EOS,AmercanGeophysical Union Trans., v.58,no.6, p.432.

Florida Geol. Survey Bull. 58, 146 p. Scott, T.M., 1988, The lithostratigraphy of the Hawthorn
Group (Miocene) of Florida: Florida Geol. Survey Bull. 59, 148 p.

Popenoe, P., and Zietz, I., 1977, The nature of the geophysical basement beneath the Coastal Plain of South Carolina and northeastern Georgia, in Rar:U<in, D. W.,(ed.),Studiesrelated to the Charles ton, South Carolina, earthquake of 1886 - A preliminary report: U. S. Geol. Survey Prof. Paper 1028, p. 119-137.
Popenoe, P., Henry, V. J., and Idris, F. M., 1987, Gulf trough-the Atlantic connection: Geology, v. 15, p. 327-332.
Prager,E.J.,andGinsburg,R.N., 1989,Carbonatenodule growth on Florida's outer shelf and its implications for fossil interpretations: Soc. Econ. Pal. and Min., Res. Repts., p. 310-317.

Sever, C. W., 1%5, TheChattahoocheeAnticlineinGeorgia: Georgia Mineral Newsletter, v. 17, p. 39-43.
___, 1966a, Miocene structural movements in Thomas County,Georgia: U.S. Geol. Survey Prof. Paper 550-C, p. C12-C16.
___, 1966b, Reconnaissance of the ground water and geology of Thomas County, Georgia: Georgia. Geol. Survey Inf,. Circ. 34, 14 p.
Sever, C. W., Cathcart, J. B., and Patterson, S. H., 1967, Phosphate deposits ofsouth-central Georgia and north-central peninsular Florida: Georgia Dept. Mines, Mining and Geology, South Georgia Minerals Program, Project Rept. 7, 62 p.

Price, R. C., and Whetstone, K. N., 1977, Lateral stream migration as evidence for region geologic structures in the eastern Gulf Coastal Plain: Southeastern Geol., v. 3, p. 129-147.
Purl, H. S., 1953, Zonation of the Ocala Group in peninsu, lar Florida (abst.): Jour. Sed. Pet., v. 23, p. 130.
___, 1957,Stratigraphyand zonation of the OcalaGroup: Florida Geol. Survey Bull. 38, 248 p.

Sever, C. W., and Herrick, S.M., 1967, Tertiary stratigraphyand geohydrology in southwesternGeorgia: U. S. Geol. Survey Prof. Paper 575-B, p. B50-B53.
Sheridan, R. E., Crosby, J. T., Bryan, G. M., and Stoffa, P. L., 1981, Stratigraphy and structure of southern Blake Plateau, northern Florida Straits, and northem Bahama Platformfrom multichannel seismic reflection data: Amer. Assoc. Pet. Geol. Bull., v. 65, no. 12, p. 2571-2593.

Puri, H. S., and Vernon, R. 0., 1964, Summary of the geology of Florida and a guidebook to the classic exposures: Florida Geol . Survey Spec. Pub. 5, revised ed., 312 p.
Rainwater, E. H., 1956,GeologyofJacksonCounty,Florida, by Wayne Moore (a review: Amer. Assoc., Pet. Geol. Bull., v. 40, no. 7, p. 1727-1729.
Randazzo, A. F., 1972, Petrography of the Suwannee Limestone: Florida Geol. Survey Bull. 54, pt. II, 13p.
Richards, H. G., and Palmer, K. V. W., 1953, Eocene mollusks from Citrus, Levy Counties, Florida: Florida Geol. Survey Bull. 35, 95 p.

Sloan, E., 1908, Catalogue of the mineral localities of South Carolina: South Carolina Geol. Survey Bull. 2, 505 p.
Smith, D.L., 1982, Review of the tectonic history of the Florida basement: Tectonics, v. 88, p. 1-22.
___, 1983,Basementmodel for the panhandle of Florida: Trans., Gulf Coast Assoc. Geol. Soc., v. 33, p. 203-208.
Stainforth, S.M., Lamb, J. L., Luterbacher, H., Beard, J. H., and Jeffords, R. M., 1975, Cenozoic planktonic foraminiferal zonation and characteristics of index forms: Univ. Kans. Pal. Contr., Art. 62, 425
P

Rock-Color ChaitCommittee, 1963Rock-color chart: Geol. Soc. Amer., New York.
Schmidt, W., 1984, Neogene stratigraphy and geologic history of the Apalachicola Embayment, Florida:

Stanley,S. M., 1970, Relation of shell form to life habits of the Bivalvia (Mollusca): Geol. Soc. Amer. Memoir, v. 125, 296 p.
Stubbs, S. A., 1941, in Cole, W. S., Stratigraphic and

151

paleontologic studies of wells in Florida: Florida Geol. Survey Bull. 19, p. 14.
Tanner, W. F., 1966, Late Cenozoic history and coastal morphology of the Apalachicola River region,
western Florida, in Shirley, M. L., and Ragsdale,
J. A. (eds.), Deltas in their geologic framework: Houston Geol. Soc., Houston, Texas, p. 83-97.
Tedford, R. H., and Hunter, M. E., 1984, Miocene marinenonmarinecorrelations, Atlanticand GulfCoastal Plains, NA: Paleogeography, Paleoclimatology, Paleoecology, v. 47, p. 129-151.

Vernon, R. 0., 1942, Geology of Holmes and Washington Counties, Florida: Florida Ceol. Survey Bull. 21, 161 p.
_ ,1951,GeologyofCitrusandLevyCounties,Florida: Florida Geol. Survey Bull. 33, 256 p.
Ward, L. W., and Blackwelder, B. W., 1979, Stratigraphic revisionofEocene, Oligoceneand lowerMiocene formations of South Carolina: South Carolina State Dev. Bd., Div. Geol., Geol. Notes, v. 23, no. 1, p. 1-32.

Tew, B.H., and Mancini, E. A., 1992a, Sequence stratigraphy as a tool in paleogeographic reconstruction: examples from the Upper Eocene and Lower Oligocene of Alabama and Mississippi (abst.): Geol. Soc. Am., Abstracts with Programs, v. 24, no. 1, p.48.

Wentworth, C. K., 1922, A scale of grade and class terms for clastic sediments: Jour. Geol., v. 30, p. 377-392.
Wicker, R. A., and Smith, D. L., 1978, Re-evaluating the Florida basement: Trans., Gulf Coast Assoc. Geol. Soc., v. 28, p. 681-687.

_ , 1992b, An integrated lithostratigraphic, biostratigraphic, and sequence stratigraphic approach to paleogeographic: examples from the Upper Eocene and Lower Oligocene of Alabama and Mississippi: Gulf Coast Assoc. Geol. Soc., v. 42, p. 381-402.
Thomas, E. P., 1948, The Jackson (Eocene) and younger
beds of west-central Mississippi: in Mississippi
Geol. Soc. sixth Field trip Guide book, p. 17-21.
Todd, R., 1952, Vicksburg (Oligocene) smaller foraminifera from Mississippi: U.S. Geol. Survey Prof. Paper 241, 53 p.
Tuomey, M., 1848, Report on the geology of South Carolina: Columbia, South Carolina.
Vail, P. R., Mitchum, R. M., and Thompson, S., 1977, Seismic stratigraphy and global changes of sealevel, Part 4: Global cycles of relative changes of
sea level, in Payton, C. E. (ed.), Seismic stratigra-
phy-applications to hydrocarbon exploration: Amer. Assoc. Pet. Geol., Tulsa, Oklahoma, p. 8397.
Vaughan, T. E., 1910, A contribution to the geologic history of the Floridian Plateau: Carnegieinst. Washington Pub. 133, Papers from the Tortugas Laboratory, v. 4, p. 99-185.

Williams, H., and Hatcher, R. D., Jr., 1982, Suspect terranes and accretionary history of the Appalachian orogen: Geology, v. 10, p. 530-536,
Winston, G. 0., 1976, Florida's Ocala Uplift is not anup-
lift: Amer. Assoc. Pet. Geol. Bull., v. 60, no. 6, p. 992-994.
Woolsey, J. R., Jr., 1976, Neogene stratigraphy of the Georgia coast and inner continental shelf: Unpubl. .Ph.D. Dissertation, University of Georgia, Athens, 222 p.
Wray,J. L., 1977,CalcareousAlgae: Amsterdam, Elsevier, 185p.
Yon, J. W., 1966, Geology of Jefferson County, Florida: Florida Geol. Survey Bull. 48,119 p.
Yon,J. W.,and Hendry, C. W., 1972,Suwannee Limestone
in Hernando, Pasco Counties, Florida: Florida Geol. Survey Bull. 54, pt. I, 42 p.
Zimmerman, E. A., 1977,Ground-waterresourcesofColquitt County, Georgia: U.S. Geol. Survey Openfilerept.77-56,41 p.

Veatch, 0., and Stephenson, L. W., 1911, Preliminary
report on the geology of the Coastal Plain of Georgia: Georgia Geol. Survey Bull. 26,466 p.

152

DEPARTMENT OF NATURAL RESOURCES ENVIRONMENTAL PROTECTION DIVISION GEORGIA GEOLOGIC SURVEY

EPOCH MIOCENE

MISSISSIPPI
w
z

CORRELATION CHART

ALABAMA
E

WESTERN PANHANDLE, FLORIDA

w
OKALOOSA CO.

E WALTON CO

JACKSON COUNTY, FLORIDA

NORTHERN FLANK CHATTAHOOCHEE
EMBAYMENT

NW

SE NW WESTERN GEORGIA

GULF TROUGH SE sw

HOUSTON & PULASKI COUNTIES, GEORGIA

NE N

S

THOMAS & BROOKS

COUNTIES, GEORGIA

SUWANNEE RIVER AREA,

FLORIDA

NW

SE

TOOMBS & TATTNALL

SOUTHEASTERN

SAVANNAH RIVER AREA,

GEORGIA

RELATIVE SEA LEVEL

COUNTIES,

COASTAL PLAIN,

GEORGIA

OUTER CONTINENTAL

CURVE

GEORGIA

SHELF

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NW

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DEPARTEMENT OF NATURAL RESOURCES ENVIRONMENTAL PROTECTION DIVISION GEORGIA GEOLOGIC SURVEY

BULLETIN 105 PLATE 2

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324'

280'

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286'

474'
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-300'
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875' TO ?
976'

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-900'

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-1200' -1300'

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DEPARTEMENT OF NATURAL RESOURCES ENVIRONMENTAL PROTECTION DIVISION GEORGIA GEOLOGIC SURVEY

BULLETIN 105 PLATE 3

STRATIGRAPHIC CROSS-SECTION FROM DOUGHERTY COUNTY. GEORGIA TO ELLAVILLE. HAMILTON COUNTY. FLORIDA

B
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256'

249 '

LIMESTONE

336' 292 '

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-900' -1000' -1100'

DEPARTEMENT OF NATURAL RESOURCES ENVIRONMENTAL PROTECTION DIVISION GEORGIA GEOLOGIC SURVEY

BULLETIN 105 PLATE 4

STRATIGRAPHIC CROSS-SECTION NEAR THE SAVANNAH RIVER FROM SCREVEN COUNTY. GEORGIA. TO THE INNER CONTINENTAL SHELF

200' 100 ' Sea Level - 10 0 ' -200'

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DEPARTEMENT OF NATURAL RESOURCES ENVIRONMENTAL PROTECTION DIVISION GEORGIA GEOLOGIC SURVEY

BULLETIN 105 PLATE 5

EAST-WEST STRATIGRAPHIC CROSS-SECTION FROM DUNCAN CHURCH. FLORIDA. TO AMCOR 6002 ON THE OUTER CONTINENTAL SHELF

D

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300' 200' 100' Sea Level -100' -200' -300' -400' -500' -600' -700' -BOO' -900' -1000' -1100' -1200'

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528 '
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470'

TO 645'

TD 1000'

. ..

\

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