Geologic atlas of the Andersonville, Methvins, and Pennington, Georgia 7.5 minute quadrangles [2003]

~OLOGIC ATLAS OF THE ANDERSONVILLE, METHVINS, A D PENNINGTON, GEORGIA 7.5 MINUTE QUADRANGLES
.~
Mark D. Cocker
In cooperation with the United States Geological Survey Cooperative Agreerttent #02HQAG0022
DEPARTMENT OF NATURAL RESOURCES Lonice Barrett, Commissioner
ENVIRONMENTAL PROTECTION DIVISION David M. Word,~Acting Director GEORGIA GEOtbGIC SURVEY
William H. McLemore, State Geologist
pen File Report O..r l
Allanta 2 00 3

GEOLOGIC ATLAS OF THE ANDERSONVILLE, METHVINS, AND PENNINGTON, GEORGIA 7.5 MINUTE QUADRANGLES
(United States Geological Survey Cooperative Agreement #02HQAG0022)
ABSTRACT
As part of the United States Geological Survey's STATEMAP Project, the Georgia Geologic Survey prepared three 7.5 minute quadrangle geologic maps during 2002 and 2003. The Andersonville, Methvins, and Pennington quadrangles are located in the Upper Coastal Plain in southwestern Georgia.
The current report contains descriptions of the stratigraphic units which have been identified and mapped in the Andersonville, Methvins, and Pennington quadrangles, as well as information on aquifer recharge zones and bauxite plus high-alumina kaolin deposits in the vicinity of Andersonville. Stratigraphic units exposed in these quadrangles range from Paleocene to Oligocene? marine sediments and Upper Paleocene and Miocene to Quaternary and Recent fluvial sediments. Recognizable marine sediments include the Lower Paleocene Clayton Formation (clay, chert and marl), Upper Paleocene to Lower Eocene Tuscahoma Formation (shale) and the Lower to Middle Eocene Claiborne Group (sandstone). Residuum of Eocene to Oligocene clastic and carbonate stratigraphic units are also present as clay, chert and sandstone but <tre too thoroughly weathered to map as separate stratigraphic units. The residuum and remnants of v3rinus stratigraphic units are mapped collectively as the Tertiary Sediments and Residuum unit. Fluvial s<1ndslone and clay of the Nanafalia Formation disconformably overlie the Clayton Formation. The Tuscthoma Formation conformably overlies the Nanafalia Formation and decreases in thickness from the southern to the northern parts of the map area where it is generally absent. Disconformably overlying the Tuscahoma, the Claiborne Group locally cuts deep channels through the Tuscahorna and deep into the Nan<tfalia Formation. Fluvial argillaceous and conglomeratic sandstones of the Miocene Altamaha Formation disconformably overlie the Nanafalia Formation, the Claiborne Group and the Tertiary Sediments and Residuum unit.
The Andersonville Fault is an unexposed, major, near-vertical fault extending roughly east-west to N 70" E through the center of the Andersonville district. This fault may extend further west than shown on Plate I. This fault appears to extend eastward across the Flint River valley. Relative movement is south side Ll]J with a displacement on the order of approximately 60 to 100 feet.
Within the current map area, recharge of the Upper Floridan aquifer is minimal to non-existent, as most of the stratigraphic units that host this aquifer are represented by a relatively impermeable residuum of clny and chert. Recharge of the Claiborne aquifer occurs principally through the exposed sand and sandstone of the Claiborne Group. To a lesser extent, recharge may also occur through the overlying argillaceous sandstone of the Altamaha Formation and through Quaternary alluvium in stream valleys. Recharge of the Clayton aquifer is expected to be minimal within the current map area, as the upper parts of the Clayton Formation consists principally of relatively impermeable clay and shale (Zapp, 1948, 1965). Also, the overlying Nanafalia Formation consists principally of impermeable kaolin or kaolinitic sandstone.
Bauxite and high alumina kaolin deposits of the Andersonville Bauxite District are found in the NanaJ"alia Formation. The currently economic portion of the Andersonville district extends approximately I0 miles in a northwest-southeast direction and has a maximum width of approximately 4 miles. Open-pit mines are developed where the Nanafalia Formation is exposed on the slopes of the deeper creek valleys and where overburden is minimal. The overlying sandstone of the Claiborne Group is soft and easily removed. Abundant large kaolin clasts in the upper sands of the Nanafalia Formation and in the basal part of the Claiborne Group overlie some ofthe kaolin deposits in this district.
Geologic hazards observed during this project and in previous mapping (Cocker, 2001, 2002) are principally related to soft sands of the Claiborne Group and soft clays of the Tertiary Sediments and Residuum unit. Rapid erosion, gullying and undercutting of the soft sands present hazards to farmlands, road11 ays, bui !dings and infrastructures such as gas, water and sewer pipe! ines. Soft clays of the Tertiary Sediments and Residuum unit can be particularly hazardous on wet unpaved roads to vehicular traffic that 111ay oause he vehicles to loose control. When dry, ruts created when the roads were wet are also hazardous by causing vehicles to bounce from one rut to another and again followed by loss of control.

CONTENTS INTRODUCTION ........................................................................................................................ ... ... ............... ........ .... I
Scope oftbe 1napping project ..................... ... ........... .... ....... ...... ................... ............. .......... ... ..................... ........ ... .. I Methods.:............ ........ ................................ .. ............... ................. ........ ..... ... ... ..... ..... ... ..................... ..... ..... ...... ... ... I Previous investigations .............................. .............. ....... ... ....... .... .. ........................ ... ................................. ......... .. .. ! PHYSIOGRAPHY AND LAND USE .................... .... ................... ............... .... .................. ........................... ..... ............. 2 SOILS .......~ ..-............ .......... ................................................................................................................................ ............ .. 3 GENERAL GEOLOGY ....................................................................................... ............. .......... ... ........ ....... .. ... ............ ..4 Geologic 'cross-sections ...... .. .............................. .. .. .... ... ......... ...................... .. ........... ... ............ ........ .......... ..... ......... 5 STRATIGRAPHY OF THE ANDERSONVILLE, METHVINS, AND PENNINGTON QUADRANGLES .. .............. 6 Upper Cretaceous ........................................................................................................................................ .... ....... ..6
Selq1a Group ......................................................... .. .............................................................................. ........... .. 7 Providence Formation (Kp) ............................................ ........... ..... ... .. .... ...... ... .......................... .. ..... ......... 7
Lower Paleocene ...... .... .. ..... .................. ........... ... ...... .. ... ...... ................ ............... ....... .... ....... .. ............. .............. ...... 7 Midway Group .......... ..................................... ...... ... .... ........................................ ............ ... ........... .. ... .......... ...... ? !=:layton Fonnation (Tcl) ................. .. ........ .... .... ... ................... ............... ..... .......... ... ............ .. .. ................. .. 7 Porters Creek Fonnation ................. .................................... ............................. ....... ............... .................. .. 7
Upper Paleocene to Lower Eocene ... ............... ......... .. ..... .................. ............................. ................................. ......... 8 Wilcox Group .. ....... ............. .... ............................... ........... ...... ... ............................. ....... ... ........ .............. ....... ... 8 Nanafalia Formation (Tnf)........................ ... ..... ....... ... ... ................. ........... ... .. ........ ... ....... ....... ... ....... .. ....... 8 1 -;~ : Tuscahoma Formation (Ttu) .................. ......... ... ..... ....... ...... .. .. ...... ... ........... ......................... ...................... 9 ! ~Piachetigbee Formation- Bashi Marl Member ...... ......................... .................. ........ .... ................ .. ..... ...... 10
Lowei to Middle Eocene ................................................................................................. .................... .... ................. 10 Claiborne Group (Tcb) ....................................................... ........ .. ...... ................... .. ....... .. .......................... ....... 10 Lisbon Formation (TI) ..................................................... ... .......... ...... ... ...... ... .. ............ .. .............. .... ........ .. .... ... 11
Upper Eocene ............................................................................................................. .... ....... .. .............. ................... 11 Eocene to' Oligocene ........ ................................ ......... ..... .. .. ... ..... ................ ... ......... .. ... ..... .. .... ................ .. ................. 12
Tertiary Sediments and Residuum (Tsr) .................................................................. ................. ............... .......... 12 Miocene .... .... .............. .. ............ ............. ...................... .......... .. ... .... ...... .. .... .............. ...... ............................... _.......... 13
Altan1aha Formation (Ta) ........................ .. .. ...... ,........ ................ ............................. ..................................... ..... 13 Tertiary-"Quaternary Alluvium (TQal) ........ ....................................... .. .... ......... ........ .. .. ... ............... ... ....................... 15 Quaternaty to Recent .. .......................... ........... .... ..... .. ..................................................... .. ............. ... ... .................... 15
Quaternary Alluvium 2 (Qal 2) .................. ............. .. ...................... .................. .......... .. ... .. ............ ................... 15 Q\mternary Alluvium (Qal) ........................ .. ............................................................. .. .. ......... ......... .. .. ... ............ 15 Alteration of primary sedimentary textures ........... .. ... ............... ................................ ... .... ............... ....... .. .. ........ ....... l6 Correlation of STATEMAP map units with earlier geologic maps ........................ .. .. ..... ............... ......... ................. 16 BIOSTRATIGRAPHY .. ... ........................................ ............ .................................... .......... .... ............. ............. ............ ... 17 STRUCTtJRAL GEOLOGY .............................. ............ .. .. .. .. .... ...... .... .. .......... .................. .... ..... ......... ............ ... .......... .. 17 ECONOMIC GEOLOGY ............................................................................................... ....... .............. .. ......................... . 18 History oJ'the Andersonville Bauxite District. .......... ......... ... .... ...... ............ ...... .. .... .. ... .... ...... ....... ... .... .. ............ ..... .. 18 Mining niethods ......................................................... ... ................... ....... ..... .... ............. ... ...... ... .... ........ ..... .... ........... 19
of Geoid~ the ore deposits ............ .... .................................. ................. .... .. .......... ..... .... .......... ....... .. ...... .. ............... 19
Minerald'gy ofthe ore deposits ........................................................................................ ..... .... ... .......................... ... 20 Origin of the ore deposits ........ ........................ ................. ..... ........ ......... ..... ... ................ ..... ............ .. .................... ... 2 1 HYDROGEOLOGY ..................... ....... .. ...... ... ... ... ...... .. ......... .. .............. ... ... .. ................ ... ...... .. ..... ... .. ..... ... ........ .. .. .. .......22 Floridan Aquifer ......... .. .... ... ... .. .................. ... ................................. ........... ... ... ........... .... ... ... ..... ..... ...... .. ..... .. .......... ,22 Claibornt' Aquifer ............................................................................................................ .. ... ....... ... ... .. ... ... ........ ....... 23 Clayton Aquifer ......... ..... ........ ...................... ........ ..... ...... .. .... .... ............ ........... ... ..... .. ..... .. .... .. ........ .... .... .. .... .... ....... 23 CretaceoLlS Aquifers ......................................................................................................... .. ... .... .. ... .......... .. .. .... .........2 3 GEOLOGIC HAZARDS ..... ... ... .......... .................. ............. ... .......................... .. ..... ..... ... .... ... ...... ....... ........ .. .. .. ..... ... .. ..... 24 SUMMARY:':.:..................... ................................................................................................... ...... ...... ........... .. .. .. ... .. .. ......2 5 REFERENCES CITED..... ................................................ ... ........... .... ..... ...... ............. .. ......... ............ .................... ..........26 APPENDIX ... .. .. .......... ..... .................... ..... .............. ................................ ......... ........... ......... ......... ............. .. .... .... .......... 31
Drill Hole Logs for the STATEMAP Program (March 2003 through July 2003) ..................... ..... ...... .... ..... .... ] I
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FIGURES
1. Location of the Americus project area in relation to the most significant recharge areas in Georgia.......................49 2. Location map of recent mapping in the Upper Coastal Plain ofGeorgia.................................................................. 50 3. Stratigraphy and related aquifers in or adjacent to the current map area........... ...... ........ ...... .................................. 51 4. Drill hok location map ............... ....... ........ ..... ........ ,................................................................................................. 52 5. Brief de,c:riptions of Tertiary to Recent map units in the current map area.............................................................. 53 6. West wall of Fowler Mine with exposures ofthe Altamaha Formation (Ta), Claiborne Group (Tcb), Tuscahoma
Formation (Ttu), and Nanafalia Formation (Tnf) .......................................................................................... ,.......... 54 7. North and west wall of the Guy-Pierce Mine ............................................................................................................ 55 8. Lower left contact of black, carbonaceous, pyritic lens with underlying kaolin pictured in Figure 7 ....................... 56 9. View of partially oxidized, black, carbonaceous, pyritic lens in Guy-Pierce Mine pictured in Figure 7 .... ...... ........ 56 10. Thinly bedded tan silt in upper part ofthe Nanafalia Formation, Fowler Mine........................................................ 57 J 1. South wall of Thigpen Mine with exposures of Altamaha Formation? (Ta), Claiborne Group (Tcb), Tuscahoma
Formation (Ttu), and Nanafalia Formation (Tnf) ......................................................... ,........................................... 57 12. Kaolin layer overlain by bedded, kaolin clast-rich conglomerates and sandy kaolin lens, Easterlin278 Mine ........ 58 13 . Nanafali:1 Formation kaolin clast conglomerate cutting kaolin in north wall ofThigpen Mine ........ ......... ............... 59 14. Closeup view of intrafonnational contact between conglomerate and kaolin in Figure 13 .......... ..... ........................ 59 15. Oefonm'.ion ofkaolin clasts related to compaction .................................................................................................. 60 16. Location of bauxite-kaolin mines in relation to a computer generated isopach map of kaolin in the Nanafalia
Formation containing I5 per cent or less coarse clastics (modified from Cofer and Fredericksen, 1982)................. 6\ 17. South v-i~lil of Easterlin 278 Mine illustrating "oxidized" upper and "reduced" lower portions of Tuscahoma
Formation (Ttu) ......................................................... ............................................................................................... 62 18. Exposure of Claiborne Group (Tcb), oxidized and reduced portions of Tuscahoma Formation (Ttu), and
underlying Nanafalia Formation (Tnf) ..................... ...... .......... .................................. .... ............. ...... ......... .............. .62 19. Undulatcry contact between "oxidized" and "reduced" portions of the Tuscahoma Formation (Ttu), south wall
of Perry l\1ine ............................ .. ............................................................................................................... .. ............. 63 20 . Exposur2 of Claiborne Group (Tcb) overlying "oxidized" and "reduced" portions of the Tuscahoma Formation
(Ttu) at Copperas Bluff on the Flint River ................................................................................................................ 63 21 . Exposure in Perry Mine exhibiting more extensive oxidation ofTuscahoma Formation (Ttu) ................................ 64 22 . North anJ east walls of the Short Mine displaying a major unconformity at the base of Claiborne Group with the
undedying Nanafalia Formation ............. ...... ........... ................................................... .... ............ .... ........... .. ............. 65 23 . Northward dipping beds in Claiborne Group sand and clay................... ......... ......................................................... 66 24. Angular lo subrounded kaolin clasts in lower portion of the Claiborne Group (Tcb) sands, eastern pit of the
Fowler !\1ine ...................................................................................................................................................... .. ..... 67 25. Herri11gbone cross-bedding in lower part of the Claibome Group (Tcb) in eastern pit of the Fowler Mine ............. 68 26. Unconfo;lllity at base of Claiborne Group (Tcb) and top of kaolin in Nanafalia Formation (Tnf) ........................... 69 27. North wall of the Fowler Mine exhibiting down cutting of channels by Claiborne Group (Tcb) through
Tuscahoma Formation (Ttu) and into sandy kaolins of the Nanafalia Formation (Tnt) and by the Altamaha Formatio11 (Ta) into the Claiborne Group ....... ........................ ........................ .......... ........ ........................................ 70 28. Northernmost exposure in Justice-Holloway Mine illustrating channel cutting at base of Claiborne Group (Tcb) into sandy kaolin and kaolin of the Nanafalia Formation (Tnf) ................................................................................ 71 29. Northern wall of eastern pit of the Fowler Mine with Altamaha Formation (Ta) overlying the Claiborne Group (Tcb) .......... ............... ........... ......... ............ ......... .... ......................... ............ ...... ... ....... ..... ....... .... ............. ........ ......... 72 30. Cont<Jct [letween Altamaha Formation (Ta) and Claiborne Group (Tcb) sandstones .. .... .......................................... 73 31. Undet'cutting of soft Claiborne Group (Tcb) sands resulting in collapse of Altamaha Formation (Ta) caprock ...... 73 32. Outcrop of clay-rich Tertiary Sediments and Residuum unit (Tsr) overlain by Altamaha Formation (Ta)
sandstone:.................................................................................. .. .............................................. .. ................. .............14 33. Quartzpcbble conglomeratic sandstone ofthe Tertiary Sediments and Residuum unit (Tsr) ....................... ........... 74
34. Contact between the AJtamaha Formation (Ta) and the Tertiary Sediments and Residuum unit (Tsr) ........ ... .......... 75 35 . Bleached .Tertiary Sediments and Residuum unit (Tsr) with iron oxide stained fracture/joints .................... .......... .. 75 36. Interbedded clay and ironstone pebble clast conglomerate at base of Altamaha Formation .......................... .... .. ..... 76 37. Close-up view of interbedded clay and ironstone pebble clast conglomerate shown in Figure 36 .................... .. ... .. 76 38. Channel .::ul of Altamaha Formation (Ta) basal conglomerate into Claiborne Group (Tcb) sandstone........ .... ...... .. 77 39. Chanllel cut of Altamaha Formation (Ta) basal conglomerate down to upper contact of the Tuscahoma
ii i

!'ormati n (Ttu) ....................... ......... .. .......................... .. ............................... .... ............. ............................. ...... ....... 77
or 40. utcr p Altamaha Formation (Ta) sandstone, Claiborne Group (Tcb) sand and Nanafalia Formation (Tnt)
kaolinitic ands tone sandy kaolin and kflolin ...... ....................... ................................... ............... ............................78 41. ' Jose-up view of contacts on the outcrop shown in Figure 40. ................ ....... ......... ............................ .. ..................78 42. Exposure of Tertiary- Quaternary A ll uvium grave l (TQal) in Drayton Quadrangle .. .............................................. 79 43. Flat 'a l1\1 ia l terrace' in southwestern corner of Byrom vili e Qua lrangle ................................................................ 79 44. !:>on cdiment deformation i11 Nanafalia Formation cong l merate ......................... ......................... ..... ..................... 80
45. Mines in the Andersonville Bauxite District.. .... .. ........................................ .. ....... .......................... .. ....... .... .............81
to 46. Removal of overburden, Claiborne Group sand, prior mining.... .. ... ................................... .... .............................. 82
47. Min iTlg of ba uxite and kaolin ............. .... ... .................. ... ........................................................ ... ........... ................ ..... 82
48. Piso lidc 'i;la uxite in Thigpen Mine..................................... ... ............................................... ................... ........... ...... ..83 49. Iron-oxide tained pisolitic bauxite from Guy-Pierce mine ........................................ ... ........................................... 83

TABU:.. 1. Percenta i!C of quadrangle containing map unit polygons ................ ... .................... ....... ..................... ....................... 5 2. Compariso n ofSTATEMAP stratigraphic terminology with that of adjacent 1: I00,000-scale geologic maps ........ 17 3. Estimat s of Resources in Millions of Dry Tonnes ................................................................................................... 19
4. Aqu ife 1 cha racteristics in the study area ............... ................... ... ........................................ .......... .... ..... ...................24

PLA E

~

1. Geologi c ma p of the Andersonville 7.5 minute quadrangle.

2. Geologic ma p ofthe Pennington 7.5 minute quadrangle.

3. Geolog_ic mo p of the Methvins 7.5 minute quadrangle.

4 . Geologic ~.ross -sectio n s

,,
...

iv

INTRODUCTION
Scope of the mapping project
The Georgia Geologic Survey mapped the surface geology of the Andersonville, Methvins, and Pennington 7.5 minute (I :24.000 scale) quadrangles in the Upper Coastal Plain of southwestern Georgia from September, 2002 through June, 2003. Mapping included both traditional field mapping and development of GIS digital databases for each quadrangle in Arclnfo format. Mapping was part of the Georgia Geologic Survey's STATEMAP Project (in cooperation with the United States Geological Survey, Cooperative Agreement #02HQAG0022).
The Georgia Geologic Survey's STATEMAP Project involves the geologic mapping of significant aquifer recharge zones in the Upper Coastal Plain (Fig. I) . These recharge zones include those of the Clayton, Claiborne, and Upper Floridan aquifers. Completed STATEMAP maps in Georgia (Fig. 2) include the Byromville, Drayton , Leslie, Bronwood, Neyami, Smithville East, Smithville West 7.5 quadrangles (Summerour, 1999, 2000), the Bottsford, Dawson, Parrott and Shellman quadrangles (Cocker, 2001), the Americus, Lake Collins, Plains and Preston quadrangles (Cocker, 2002), and the Andersonville, Methvins and Pennington quadrangles (this report). These quadrangles provide data for the compilation of a 1:1 00,000-scale geologic atlas of the Americus area (Fig. I) . Figure 3 provides a summary of the stratigraphy and related aquifers in or adjacent to the Americus area.
Methods
Field methods used to produce the geologic maps (Plates 1 - 3) involved mainly the description and mapping of roadside Ulitl :';:lpS and exposures as well as exposures in the bauxite/kaolin mines of the Andersonville district. Lithologic descriptions of well cuttings from the Georgia Geologic Survey technical files and published descriptions from Herrick ( 1961) were used to help construct the geologic cross-sections illustrated in Plate 4. The Georgia Geologic Survey drilled a series of shallow core holes (less than or equal to 50 feet) that were designed to: l) confirm the mapped geology, 2) determine depth to contacts, and 3) examine relatively non-weathered lithologies particularly in areas with limited exposures . Drill hole logs for these holes are in the appendix . Locations are on the accompanying geologic maps.
The drill rig used in this investigation is "a Formost Mobile model B-59 rig. Coring was done with 4 1/4 inch i.d. hollow stem augers equipped with a wireline, continuous coring system. The core barrel is latched in just above the bottom auger fli ght and extends downward, teminating with a punch shoe that protrudes a few inches below the auger cutter head. The core barrel is attached to the latching mechanism with a bearing that allows the barrel to remain stationary as the augers and cutter head revolve around it. As the rig augers, the punch shoe is pushed into the formatior, <1head of the cutter head, collecting an undisturbed core. The system is intended for use in 5 foot intervals, but \ve find that it is much more efficient when operated in 2.5 foot intervals. Recovery rate is nearly I00%" (Mark Hall, personnel communication).
A significant part of this project involved production of digital mapping products and documentation of the digital techniques. Outcrop locations were digitally plotted directly from field maps using Arclnfo 8.1. Additional field geologic cl <1 ta were compiled in an Arclnfo database . Digital geologic maps were compiled on-screen using the outcrop d<lta and cross-sections (Plate 4). Arcplot programs were written to prepare hard copi es of each individual geologic m<lr' (Plates l - 3). Geologic cross-sections were constructed on gridded mylar, scanned, digitally traced and graphically completed in CorelDraw 7.0. Documentation regarding the development of the Arclnfo databases as well as Arcl11fo export files of those coverages are in preparation . Development of the Arclnfo databases for the current map area generally follows the procedures documented for the previous STATEMAP quadrangles in Georgia (Cocker, 1999b, c, d and 2000a, b, c, d) .
Lithologic descriptions and stratigraphic terminology (Fig. 4) for this current portion of the STATEMAP Project generally follow that of Cocker (200 1, 2002), Cofer and Manker (1983), Hetrick ( 1990), Marsalis and Friddell ( 1975), Owen ( 1956), Reinhardt and others ( 1994) and Summerour (1999, 2000), Zapp ( 1965).
Previous inn~tigations
Recent n:gional scale maps (1:100,000) are located in relation to the STATEMAP quadrangles in Fig. 2. The quadrangles mapped during this current project overlap a portion of the geologic map of the Americus 30' x 60' quadrangle (Reinhardt and others, 1994) and are adjacent to the Butler geologic atlas (Hetrick, 1996). Those maps do not diiTet'entiate strata above the Tuscahoma Form<ltion (Paleocene) and are thus difficult to correlate with the

younger strata found in the current map area. An earlier detailed geologic map (Zapp, 1965) focused on the Andersonville Bauxite District and benefited from an intense drilling program by the U.S. Bureau of Mines. Cofer and others ( 1976), Cofer and Fredericksen (1982), Cofer and Manker ( 1983) reevaluated the bauxite and kaolin deposits in light of new data on the mineralogy, sedimentology and paleoenvironmental studies obtained primarily from approximately 600 exploration drill holes and mine exposures available at that time. Geophysical studies also contributed to that reevaluation. The adjacent Byromville, Drayton and Leslie SE quadrangles (I :24000 scale) were mapped at the beginning of this STATEMAP project (Summerour, 1999), and the adjacent Americus quadrangle was mapped last year (Cocker, 2002).
The Geologic Map of Georgia (Georgia Geologic Survey, 1976) and the I :500,000-scale Digital Geologic Map of Georgia (Cocker, 1999a) provide a general view of the surface geology of the map area. Digital overlays of the geology and lDpography at I :24,000 scale display a rough correlation between the I :500,000 scale geology of the state map and the detailed topography. During this investigation several errors were identified on the Geologic Map of Geoigia (Georgia Geologic Survey, 1976). Three polygons located at the bottoms of creek valleys in the Andersonville district are depicted as being Tuscahoma Formation but are actually Clayton Formation.
Other geologic investigations in or near the present map area are concentrated mainly on the stratigraphic sections exposed along the Chattahoochee and Flint Rivers. Geologic reports that provide pertinent information or aid in interpretotion of the present mapping include local ond regional studies by Beck ( 1982), Beck ( 1949), Bybell and Gibson ( 1982), Cofer and Fredericksen (1982), Cofer and Manker (1983), Cramer and Arden (1980), Davis ( 1974), Eargle ( 1955), Fritz ( 1989), Gohn and others (1982), Grumbles ( 1957), Herrick and Vorhis (1963), Hetrick ( 1990, 1992, 1996), Hetrick and Friddell (1990), Huddlestun (1985, 1988, 1992a, b, 1993), Huddlestun and Hetrick (1979, 1985, 1991), Huddlestun and others (1974), Huddlestun and Summerour (1996), Luckett (1979), Marsalis and Friddcll ( 1975), Owen (1956, 1963), Pickering (1966, 1970), Reinhardt (1982, 1986), Reinhardt and Gibson (1981), Reinlwrdt and others (1994), Rountree and others (1978), Summerour (1999), Toulmin and LaMoreaux (1963), Zopp ( 1948, 1965), and Zapp and Clark (1965).
Subsurface geologic investigations of the study area include descriptions of shallow core holes drilled in 2003, as well as, older well logs and hydrologic reports. Lithologic descriptions of core samples and cuttings from wells in Dooly, Macon, Schley and Sumter Counties were obtained from published data by Herrick (1961 ), and unpublished dota by Herrick, Owen and anonymous authors (Georgia Geologic Survey technical files, Atlanta, Georgia). Clnrke and others (1983, 1984), Gorday and others (1997), Johnston and Miller (1988), Long (1989), McFadden and Perriello (1983), Mitchell (!981), Reinhardt (1982), and Vorhis (1972) examined the hydrology and hydrogeology of the region.
Cocker (200 I) summarized the general relationships of soils in Terrell and Sumter Counties to the parent source rocks as depicted on the geologic maps for the Bottsford, Dawson, Parrott and Shellman quadrangles. These relationships a1e similar to those observed for most of the soils in the Andersonville, Methvins and Pennington quadrangles ..In a broad sense, the general soil map of Sumter County (Pilkinton, 1974) is similar to the geology mapped in the present investigation.
PHYSIOGRAPHY AND LAND USE
The Andc'I'Sonville, Methvins, and Pennington quadrangles lie within the Coastal Plain Physiographic Province. Terrain in the Andersonvi lie, Methvins, and Pennington quadrangles is characteristic of the edges of the Dougherty Plain physiographic district and consists of gently to moderately rolling upland surfaces incised by the Flint River and a few major streams, i.e. Camp, Lime, Mountain and Sweetwater Creeks, and their tributaries.
The Flinl River valley is a major physiographic part of the current map area. Broad flat areas adjacent to the Flint River ar.; suggestive of former river terraces. The elevation of the current flood plain of the Flint River ranges from 240 feel in the northern part of the Methvins quadrangle to 260 feet in the northern part of the Pennington quadrangle (Plates 2 and 3). The present width of the Flint River flood plain is approximately 1.5 miles. The elevation bf remnants of the most recent terrace above the current flood plain ranges from approximately 250 feet in the southem pnrt of the Pennington quadrangle to approximately 280 feet in the no11hern pa11 of the quadrangle. Additional bmJd flat areas at elevations of approximately 290 to 300 feet and 315 to 340 feet in the Pennington quadrangle (!'late 2) may be former river terraces. Present field mapping and core drilling did not locate any identifiable terrace sediments in the Pennington quadrangle or across the Flint River in the Byromville quadrangle. With the exce[.Jtion of one core hole in the Drayton quadrangle, core drilling into parts of the previously mapped terraces intersected only sediments belonging to the underlying Tertiary stratigraphy. These terraces may be erosional, i.e. cut into the underlying Tertiary sediments by the meandering Flint River. A few, thin remnants of probable, older flood plain deposits of the Flint River were found locally at elevations of 320 to 350 feet. Previous
2

maps of this part of the Flint River Valley (Hetrick, 1996, Reinhardt and others, 1994, and Summerour, 1999, and Zapp, \965) define broad flat areas and hill slopes as being overlain by river terrace deposits. If these are former terraces of the Flint River, the Flint River Valley could have been as wide as 5.5 miles, more than 3 times the current, recognized width.
Many parts of the upland interfluvial areas, particularly south of the Andersonville district, are covered by an increasingly thicker layer of indurated argillaceous sandstone of the Miocene Altamaha Formation. This sandstone has served as a cap rock protecting significantly softer sand and sandstone of the underlying Eocene Claiborne Group. Down cutting of the northern creeks, i.e. Camp, Mountain and Sweetwater Creeks, is more pronounced than that of Lime Creek and results in slopes of the northern streams in these quads being relatively steep while those slopes to the south are relatively gentle. Valleys of the larger streams, i.e. Camp, Lime, Mountain and Sweetwater Creeks, ate typically on the order of 0.25 miles or less wide. Breaching of the Altamaha sandstone cap resulted in rapid down cutting and erosion of the underlying sands. New base levels have apparently been established in the major stream valleys. Elevation of the upland (interfluve) areas rises gradually from approximately 300 feet in the southeast part of the Methvins quadrangle to 500 feet in the western part of the Andersonville quadrangle. That approximate 200-foot change in elevation contrasts with the 130-foot change in elevation of the flat stream valleys (about 250 to 380 feet). Erosion ofthe soft sands of the CI<Jiborne Group can be quite rapid, with at least some of the erosion obset ved adjacent to the major streams attributable to poor agricultural practices during the past.
Much of: he bottom lands in the major creek valleys is relatively swampy and is underlain by the shale and clay of the Tuscahoma or Clayton Formations. Straight stretches of Lime Creek and one of its tributaries in the southeast corner of i he :Ylethvins quadrangle appear to be man made. This was an agricultural practice in the early part of the 1900's to eliminate meanders and swampy land in flood plains by straightening the drainage system. Swampy, flat, upland areas', particularly in the southern part of the Methvins quadrangle may be underlain, in part, by clay-rich residuum oftlte Tertiary Sediments and Residuum unit.
During this and the earlier investigation by Cofer and Manker ( 1983), the unusual drainage pattern defined by the major stresms was observed. Long, linear trends with abrupt changes in orientation in Buck, Camp, Mountain and Sweetwater Creeks, as well as some of their tributmies, suggest some structural control in their orientation.
The area covered by the Andersonville, Methvins, and Pennington quadrangles is used for agricultural products which include peanuts, corn, soybeans, cotton, pecans, beef cattle, hogs, sawlogs, and pulpwood (Pilkinton, 1974) and for minir.g of bauxite and kaolin. Mining operations are generally restricted to the occurrence of bauxite and kaolin in th.c Nanafalia Formation where that unit is exposed, or near the surface, in the Andersonville and Pennington Q]Uadrangles. Americus to the southwest and the Montezuma- Oglethorpe area to the northeast are the major population centers and provide services to the surrounding areas.
SOILS
Because agriculture is a major industry in the current map area, soil and water supply are very important and have received much attention. The broad, relatively flat upland areas are generally well suited to agriculture because of the soil <:li:d topography. Slopes bordering the Flint River and its tributaries are generally underlain by sandy geological Llllits and are not as well suited for agriculture. This section briefly describes the soils in regards to their source materials and the information the published soil data can contribute to geologic mapping in the area.
Soi Is in the map area reflect intensive subtropical we<~thering of the exposed Tertiary stratigraphy. Soils in the broad upland areas, particularly in the southern parts of the Andersonville and Pennington quadrangles and most of the Metlwins quadrangle, are derived mainly from gravelly sands and sandy clays of the Altamaha Formation. Locally, more stony and clayey soils were derived mainly from chert and clay residuum resulting from weathering of Eocene and Oligocene carbonate rocks. Generally, these soils are interspersed with those derived from the Altamaha Formation as erosion has exposed the residuum. Sandy soils, derived principally from sandstone of the Claiborne Group and the Nanafalia Formation, are found at lower elevations in creek valleys particularly in the Andersonville and Pennington quadrangles and on slopes extending down to the Flint River. Clay rich soils on the lower slopes and creek bottoms are derived from the Tuscahoma, Nanafalia and Clayton Formations. Broad flat areas found <tt lower elevations in the flood plain of the Flint River are underlain by alluvium of the Flint River (Plates 2 and 3). Soils derived from this alluvium may be sandy, clayey and/or organic rich. Broad flat areas found at higher elevations in the Flint River Valley may be alluvial terraces of the Flint River (Plates 2 and 3). Some parts of these terraces may be underlain by Flint River alluvium similar to that described above. Other areas may erosional in nature and be underlain principally by sand of the undel'lying geologic unit, generally the Claiborne Group or Nanafalia Fol'mation.
Soils may be classified based on diagnostic surface horizons, epipedons, and subsurface horizons. The principal
3

types of soil found in the southeastern United States are Ultisols. This soil order is characterized by argillic or kandic horizons and low base saturation. An argillic horizon is defined as a subsurface accumulation of high-activity silicate clays that have moved downward or translocated ftom the upper horizons or have formed in place (Brady and Wei!, 1999). An epipedon overlying a kandic horizon has commonly lost most of its clay content. A kandic horizon is a diagnostic subsurface horizon characterized by an accumulation of iron and aluminum oxides as well as low activity, strongly acid, silicate clays (e.g., kaolinite). Low activity clays demonstrate low cation-holding capacities (< 16 cmolclkg clay). Clays are often found as coatings on pore walls and surfaces. Ultisols formed under conditions of fluctuating wetness have horizons of iron-rich mottled material called plinthite. As long as it remains moist, plinthite is soft and easily dug. When exposed and dried in air, plinthite hardens into an ironstone. Ultisols are formed under wet, tropical conditions and usually under forests. Most are developed on old land surfaces (Brady and Wei!, 1999).
Intensive subtropical weathering has produced a commonly striking profile in the soils and subsoils, particularly in those derived from the Altamaha Formation and, to a lesser extent, those derived from the Tertiary Sediments and Residuum unit. The upper portion ofthe profile is commonly sand-rich or slightly argillaceous sand/sandstone. This portion of the pmfi le may range from 0 to I0 feet thick. Thickness of this sandy portion of the profile is commonly dependent on the degree of erosion (Long and Baldwin, 1915). A clay rich zone is generally found beneath the upper sandy zone or may be present by itself with the upper, sandy unit having been removed by recent erosion. Clay particles are mobilized by downward percolating surface water and accumulate in the subsoil. Mottling, probably rel<lted oxidizing by ground water, is usually developed in the clay-rich lower zone. Irregular concentratioils of iron-oxide cemented sediments (plinthite) may be developed in this lower clay-rich zone. These have formed in situ and result from remobilization of iron from other parts of the soil and subsoil. Cocker (200 1) described and interpreted the vertical distribution of particle sizes in the main soil types of the Bottsford, Dawson, Parrott and Shellman quadrangles.
GENERAL GEOLOGY
In a broc;d sense, the surface geology of these three quadrangles consists of the Miocene Altamaha Formation overlying progressively older map units from the southern edge of the Methvins quadrangle to the northern edges of the Andersonville and Pennington quadrangles. This results from a gradual, regional dip to the southeast and an erosional unconformity beneath the Altamaha Formation. Economically important, open-pit bauxite and high alumina kaolin mines are located in the Andersonville bauxite district which extends approximately east west to slightly northwest across the Andersonville and Pennington quadrangles and into the adjacent Ideal South quadrangle. .An arcuate, high-angle normal fault, the Andersonville fault cuts through the Andersonville bauxite district. Relative movement is south side up, resulting in more bauxite deposits being brought to the surface. In addition tc the present flood plain and a slightly older alluvium in the Flint River valley, broad, flat terrain at higher elevations adjacent to the Flint River in the Pennington quadrangle suggest the presence of older river terraces. Erosional unconformities, facies changes, surface weathering, groundwater-induced alteration, lithologic similarities of some sedimentary units, and paucity of outcrops, as well as various combinations of these factors adds complexities to the identification and mapping of the rocks in these three quadrangles.
As in previously mapped quadrangles located principally to the south (Cocker, 2001, 2002 and Summerour, 1999, 2000), the youngest Tertiary sediments, represented by predominantly argillaceous sandstone of the Miocene Altamaha Formation, formerly covered most if not all of the present map area. Isolated remnants of residuum of Eocene and Oligocene age sediments represented mainly by clay and chert are exposed in parts of the Andersonvill(, Pennington and Methvins quadrangles. Generally unconsolidated or poorly cemented sandstone of the Middle Eocene Claiborne Group is generally found on slopes in the Andersonville, Pennington and Methvins quadrangks 1vith the best exposures in the bauxite-kaolin open-pit mines in the Andersonville and Pennington quadrangles. Shale, clay and siltstone of the Upper Paleocene Tuscahoma Formation are uncommonly exposed in the Andersonville and Pennington quadrangles. The best exposures of the Tuscahoma Formation are found in the Andersonville bauxite-kaolin open-pit mines, also. Further to the north, The Tuscahoma Formation thins progressively to the north and is absent in Andersonville bauxite-kaolin open-pit mines in the southern part of the Ideal South quadrangle.
Progressively older Tertiary rocks are exposed in the northern parts of the current map area. Kaolinitic, micaceous, noss-bedded sandstone and economic deposits of bauxite and high-alumina kaolin of the Upper Paleocene Nanofalia Formation are found predominantly in the Andersonville and Pennington quadrangles. Shale and clay of the Lower Paleocene Clayton Formation are soft and are poorly exposed. Drill hole data and a few
4

exposures in the Flint River valley depict the limited distribution of the Clayton Formation (Zapp, 1965) in the Anderso nville and Pennington quadrangles.
Subsurface, drill log data indicate an unknown thickness of the Upper Cretaceous stratigraphic section is present below the present map area. Exposures of the Providence Formation immediately to the north of the map area, in addition to the drill data suggest that the Providence Formation underlies the Clayton Formation.
Regional dip of Tertiary sediments older than the Altamaha Formation is on the order of20 to 30 feet per mile to the so uthe<1st. Although the lower contact of the Altamaha Formation is locally very irregular because of an erosional disconformity with underlying sediments, it dips generally gently to the southeast, also. The Tertiary section increases in thickness relatively uniformly from NW to SE from less than I00 feet in the Andersonville quadrangle to approximately 450 feet in the Methvins quadrangle (geologic cross-sections A-A' -A" and B-B '-B"BB-BB ' -BB" in Plate 4).
A summary of map unit areas for each quadrangle (Table 1) indicates both the relative change from exposed older units in the northwest (Andersonville quadrangl e) to the exposed younger units in the southeast (Methvins quadrangle) , as well as the influence of the wide valley and associated alluvium of the Flint River to the east in the Pennington and Methvins quadrangles. The differences from northwest to southeast are related to the degree of erosion and dissection, as well as regional dips that expose older sediments in the northwestern quadrangles (Plates I - 4). In the Pennington quadrangle perhaps as much <lS 38 percent of the area may be covered by alluvium, most of which is in the Flint River valley.

Table 1. Percentage of quadrangle containing map unit polygons. Data is derived from Arclnfo databases created for each quadrangle's geologic map. These numbers should be regarded as estimates because much of the geology is unexposed, and the geologic mapping is pro_jected in inaccessible areas .

,. ~

Andersonv ilie

Methvins

Pennington

Water

0.18%

0.86 %

1.55 %

Quaternary Alluvium

4.32%

11.81 %

23.89%

Qu!lternary Alluvium 2

0.0%

0.0%

6.85%

Alt!lmaha Formation

30.22%

73.49%

18.93 %

'Tertiary Sediments and Residuum
Claiborne Group

0.62% 16.26 %

1.70% 12. 14 %

0.42% 37.15%

Tuscahoma Formation

0.73%

0.003%

0.62%

Nanafalia Formation I 11'1 Clayton Formation

47.33% 0.33%

0.0% 0%

10.37% 0.21 %

Geologic cross-sections
Lithologic descriptions by Herrick (1961 and unpublished data), Owen (unpublished data), anonymous logs (GGS unpublished data) , a cross-section of the Andersonville district (Zapp, 1965) plus field observations in and adjacent to tPte current map area provided data for the geologic cross-sections A-A' -A" and B-B' -B"-BB-BB' -BB" (Plate 4). Herrick and Owen based their descriptions and interpretations on well cuttings collected from water supply wells dri lied from the 1940s through the early 1960s. As their well cuttings were usually sampled at ten-foot intervals, Herrick and Owen described most unit thicknesses based on those intervals. Because of differences in sample recovery and interpretations, lithologic descriptions as well as stratigraphic picks may vary from one well to another, and correlation between wells and between surface and well data is not necessarily optimal.
Accuracy of well locations is highly variable. Most of these wells were drilled for water supply purposes, and
some wells w91:e apparently not surveyed. Prior to the 1970's, 7.5 minute quadrangle maps were not yet available for

5

this part of Georgia, and well locations were marked on Georgia Department of Transportation county road maps. Well locations were subsequently transferred to other maps in the Georgia Geologic Survey technical files. One GIS database was developed from wells plotted on Georgia Department of Transportation (DOT) county road maps which are located in the Georgia Geologic Survey technical files. Well locations were then plotted on digital images of each DOT county road map, and attributes were added in ArcView.
Another GIS database was developed from an earlier, unpublished digital database of GGS numbered wells that were located by latitude and longitude. A digital plot of both of those databases together shows some of the same wells from each database to Iie close to each other while others are either missing from one of the databases or they are relatively far apart. A comparison with data on the well log sheets as well as the probable location for a well on a topographic base map, suggests that the database that contained latitude and longitude data for the GGS wells is generally lhe more accurate database.
The geologic map of Reinhardt and others (1994) shows well locations with circles. Wells used by Reinhardt and others (1994) in their mapping and cross-sections are labeled. Unlabeled wells on the map of Reinhardt and others ( 1994) that are in the vicinity of the wells described in the previous two paragraphs are assumed to reference the same wei ls. Locations of the wells on Reinhardt's map may coincide with the locations from the DOT maps, with the unpublished digital database, or are in the vicinity of both of those locations. Well locations from Reinhardt's map were used to aid in the selection of which well locations from the other two databases were used for the cross-sections.
Locations of wells from the DOT maps were used when those wells were not included in the GGS digital database. Locations of all the wells in the current map area and adjacent quadrangles minus the duplicate wells are shown on the inset map in Plate 4. The numbered wells were used to construct the cross-sections. Most of the other wells sho\\'n on the inset map either did not have a lithologic log or the log was of too poor quality to be used.
Section A-A' -A" was constructed along the same section line as that of Zapp ( 1965). The topographic profile was redrawn to reflect the presently more detailed top ographic base maps, the elevations were rescaled to I inch = l00 feet, the horizontal distance rescaled to I inch = 2000 feet, and surface geology redrawn in accord with the current mapping. Some of the contacts and subsurface relations depicted by Zapp benefited from the 1, I00 exploration dri II holes completed during the evaluation of the Andersonville district reported by Beck ( 1949), Zapp ( 1948, 1965) and Zapp and Clark ( 1965).
From March to May 2003, twenty-two core holes(</= 50 feet) were drilled to aid in the delineation of contacts and identily uf geologic units in the current map area cllld in the previously mapped Byromville and Drayton quadrangles I Summerour, 1999). Drill holes in the Byromville and Drayton quadrangles were needed to address differences in mapping encountered between this year's mapping and that done in the Byromville and Drayton quadrangles. Descriptive logs of each well and their interpreted stratigraphy are in the Appendix. Locations for the wells in this) ear's program are plotted on Plate 2 and Fig. 4.
STRATIGRAPHY OF THE ANDERSONVILLE, METHVINS AND PENNINGTON QUADRANGLES
Exposed stratigraphic units in the study area include the Lower Paleocene Clayton Formation (Tel) and Upper Paleocene Nanafalia Formation (Tnf), Upper Paleocene to Lower Eocene Tuscahoma Formation (Ttu), Middle Eocene Claiborne Group (Tcb), Eocene - Oligocene Tertiary Sediments and Residuum unit (Tsr), the Miocene Altamaha Formation (Ta), Te1tiary- Quaternary Alluvium (TQal), Quaternary Alluvium 2 (Qal 2) and Alluvium (Qal). The Tertiary Sediments and Residuum unit (Tsr), is believed to consist of unidentified portions of Eocene and Oligocene stratigraphic units and their residuum . In addition to the Quaternary to Recent sediments in the stream anci Flint River valleys, two or more older alluvial deposits may be present. Descriptions of these map units are summarized in Figure 5. Stratigraphic units identified only in well logs include the Upper Cretaceous Providence Formation (Kp), the Middle Eocene Lisbon Formation (TI) and Upper Eocene Ocala Group (To).
Upper Cretaceous
Upper Cretaceous sediments are not exposed in the map area, but are found in the quadrangles that lie immediately north and west of the Andersonville and Pennington quadrangles . These sediments were logged in deeper drill holes to the north and west in the Andersonville and Pennington quadrangles.
6

Selma Group
Pr01irlence Formation (Kp)
The Providence Formation is the youngest Upper Cretaceous unit recognized in the vicinity of the current map area. Owen ( 1956), Reinhardt and others (1994), Hetrick (1996) and the Georgia Geologic Survey (1976) map the Providence Formation in the quadrangles immediately to the north and west of the current map area. Reinhardt and others ( 1994) describe the Providence Formation as pale yellow, cross-bedded, fine to coarse sand with interbedded, yellowish brown to olive, massive to thinly bedded sandy clay lenses. This unit is subdivided in crosssections into tvvo lithofacies. One lithofacies is a cross-bedded, coarse quartz sandstone with locally abundant heavy minerals. The other lithofacies is a laminated to massive, highly micaceous, locally carbonaceous, silty clay and clayey fine sandstone that may be burrowed or bioturbated. Thickness of this unit may range from 83 to 267 feet (Marsalis and Friddell, 1975; Reinhardt and others, 1994).
Lower Paleo-.:cne
Midway Group
Clayton Formation (Tel)
The Clayton Formation in or adjacent to the map area has been described in the literature from limited outcrops and drill hole;, but was not observed in this investigation. The Clayton Formation is described as being composed of yellow to bull-brown, interbedded, micaceous silty clay, calcareous sandstone, and bioclastic limestone (Reinhardt and others, 1994). The limestone is locally well-crystallized and well-cemented or vuggy and is composed of molluscan and bryozoan fragments. Cofer and Manker (1 983) describe the Clayton Formation as "dark-gray, shaley, marine clay generally overlying an argillaceous, arenaceous Iimestone and gray clayey sand containing biostromes of oysters and detrital accumulations of shell fragments" . A thin, 7- to 8-foot thick, indurated, coquinoid, sandy limestone wr,s present in all the drill holes that penetrated the Clayton Formation (Cofer and Manker, 1983). Sporomor[JhS from the upper clay unit are Lower Paleocene (Cofer and Fredericksen, 1982).
In outcr(jJS in the Plains and Preston quadrangles , the Clayton Formation is represented principally by oliveblack to black: clay (Cocker, 2002) . Locally, small pieces of whitish, rotten chert occur in the shale and are indicative of the former presence of carbonate. Brecciated shale in a clay matrix may be a result of solution collapse. Strongly distorted bedding also suggests collapse due to dissolution of carbonates. In a drill core from the Plains quadrangle (Cocker, 200.2), similar argillaceous, che11y sediments were found to overlie a "marl" consisting of hard, light gray, fossiliferous limestone and minor chert fragments in a reddish-brown clay. As the drill rig was only able to penetrate a few feel of 'this material, the extent of the "marl" and the remaining stratigraphy of the Clayton Formation are unknown. The cross-section of the Andersonville bauxite district (Zapp, 1948, 1965) suggests thin clay overlies the limestone.
Maximu111 thickness of this unit may range from 50 feet (Zapp, 1965) to 60 or 70 feet (Cofer and Manker, 1983). Cross-s~ctions by Rheinhardt and others (1994) and by Zapp (1948 and 1965) illustrate karst-related, local variations in thickness and regional thinning of the Clayton Formation. Regionally, the maximum thickness of the Clayton Forntntion may range from l 0 to 165 feet (Marsalis and Friddell, 1975; Owen, 1956; Reinhardt and others, 1994), in part clue to extensive karstification. Because the study by Cofer and Manker benefited from logging of exploration drill holes located over a more representative portion of the district than that of the World War II era drilling, the ,thicknesses noted by them are probably a better indication of the actual thickness of the Clayton Formation.
Porters Creek Formation {Tpc)
An olive-black, compact, highly glauconitic, fissile clay to silty clay that may be the Porters Creek Formation is locally present at the top of the section commonly mapped as Clayton Formation in this part of Georgia (Owen , 1956 ; Reinhat'clt and others, 1994). Thickness of this unit, where present, is 3 to 33 feet. Owen ( 1956) described the upper clay as light gray, slightly sandy with irregular 1ed splotches. Clay that may have been assigned to this unit is described Ji:om some of the drill holes that penetrate the Clayton Formation in the present map area. This clay is apparently included as the upper part of the Clayton Formation by Cofer and Manker (1983).
7

Upper Paleocene to Lower Eocene
Wilcox Group
Na11ajalia Formation (Tnj)
The Upper Paleocene Nanafalia Formation is descr ibed as consisting of two coeval Iithofacies subdivided into the Baker Hill and Nanafalia Formations (Reinhardt and others, 1994). The Baker Hill Formation is described as fine to coarse, light greenish-gray to yellowish-brown , highly micaceous quartz sand that interfingers with light greenish-gray to black sandy clay and massive kaolin beds. Trough cross-bedding and abundant rounded to subangular clay clasts are commonly found in the sandy intervals. Commonly, thick-bedded to massive clay is locally more than 33 feet thick and contains sand or silt l<1minae. Scattered thick lenses of kaolin contain bauxite. According to Reinhardt and others (1994), the Nane1falia Formation is present only in the subsurface. This unit contains greenish-gray, micaceous, fine- to coarse-grained, glauconitic, fossiliferous, massive bedded, fossiliferous quartz sand with local clay lenses.
Huddlestun and others (1974) assign Nanafalia- age sediments to the Gravel Creek Member, the marginally marine to no!1marine facies of the Nanafalia Formation (1-l uddlestun and others, 1974). Nanafalia-age sediments in the Andersonv ilie di strict were assigned to the Nanafa Iia Formation by Zapp (1965) and Cofer and Manker (1983). Within the current map area and areas to the west (Cocker, 2002), stratigraphic divisions are simplified, and Nanafalia-age sediments were mapped as the Nanafalia Formation.
From surfe1ce exposures and drill cores, the contact between the Clayton and Nanafalia Formations is described as unconforn~able (Cofer and Manker, 1983). Clasts of montmorillonite clay from the underlying Clayton Formation are commonly embedded in the overlying sandy kaolin of the Nanafalia Formation.
In the Andersonville district, this formation is described as "a thick series of light-colored, medium to coarsegrained, kaolinitic, micaceous sand and lenticular kaolin and sandy kaolin" (Cofer and Manker, 1983). Drill holes to the south anr! west of the main part of the district intersect dark-gray, lignitic, clayey sands with little or no kaolin. Reddish purple splotches in the kaolin are caused by secondary hematite and pyrite.
Despite its widespread distribution in the Andersonville and Pennington quadrangles (Plates 1 and 2), the Nanafalia Formation is generally poorly represented in outcrops and is not exposed in the Methvins quadrangle. The best exposures are found in the open-pit mines in the Andersonville bauxite district.
Exposures of the Nanafalia Formation in the open-pit mines examined in this investigation suggest a rather complex depositional hi story. The upper part of the Nanafalia Formation consists generally of cross-bedded, fine to very coarse, light greenish-gray to yellowish-brown , kaol initic, highly micaceous, unconsolidated, quartz sand (Fig. 6). Beneath 1hat sand may be a thin sequence of interbedded layers of yellowish-brown to tan silt/mud and sand (Figs. 6, I0). Commonly below that silt and mud and possibly grading upward into it are lenses and channels of thinbedded to massive, black, carbonaceous, pyritic silt and mud (Figs. 6, 7, 8, 9, 11). Below that are more crossbedded, kaolinitic sandstone or sands. These kaolinitic sands may grade downward to sandy kaolin and eventually into massive kaolin (Fig. 6). Bauxite may occur within the massive kaolin and is more commonly associated with the thicker kaolin bodies . The lower parts of the Nanafalia Formation are not exposed in the mines, because the kaolin is onl) excavated down to where the increase in sand content causes mining to be uneconomic. Also, inactive mines are quickly flooded . Descriptions indicate the kaolin becomes increasingly sandier and grades into kaolinitic sand at the: bas~ of the Nanafalia Formation (Cofer and Manker, 1983; Hammack, personal communication, 2002 ; Zapp, 1965),
lntrafon;,ltional disconformities are also present where channels of less kaolinitic sands cut down into the more kaolinitic cmnds or kaolin (Fig. 11). Younger, kaolin clast conglomerates in the Easterlin 278 mine and the Thigpen mine cut clown into the massive kaolin (Figs. 12, 13, 14, 15). These channel conglomerates contain soft and hard kaolin clasts, in fine to coarse-grained sand. Deformation of the softer kaolin clasts are apparent (Fig. 15). As noted above, some ol'the channels are filled with black, lignitic, pyritic silt and mud (Figs. 6, 7, 8, II).
Locally, cross-bedded sand of the Claiborne Group cuts down through the Tuscahoma Formation and into the Nanafalia Formation (Figs. 22, 27). The upper sand and kaolinitic sands may not be present, perhaps removed prior to or subseqLJcnt to deposition of the overlying Tuscahoma Formation. In the northern part of the Andersonville district, much of the overlying sands of the Nanafalia Formation and all of the Tuscahoma Formation were removed prior to deposition of the Claiborne Group (Figs. 22, 26, 28). Channels filled with Altamaha Formation sediments that had cut down into the Nanafalia Formation were also observed (Figs. 40, 41 ). Although generally conformable with the underlying Nanafalia Formation, channels filled with Tuscahoma Formation sediments were described by
8

Cofer and M<mker (1983). None of these were observed during the current mine exposures. Within the Andersonville district, measurements of the thickness of the Nanafalia Formation range from 50 to
90 feet (Zapp, 1965), 30 to 80 feet (Cofer and Manker, 1983), and 20 to 160 feet (Reinhardt and others, 1994). In the Plate 4 cross-sections, the thickness ofthe Nanafalia Formation may range from 40 to 120 feet.
Analysis of the sedimentologic features of the Nanafalia Formation in the Andersonville district suggest that the sand and kaolin were deposited in a southeasterly trending, shallow, near-shore, low-energy, marine or estuarine basin (Cofer and Manker, 1983). Kaolinite is the dominant clay mineral in the central and northern parts of the district. illite is generally more abundant in the lower patt of the formation and in the southern part of the district where the cl:1y bodies have not been exposed or near to the surface. Montmorillonite, representative of a more marine environment, is more prevalent to the south. Bertherine in the southern part of the district and glauconite in the western part of the district, also suggest the sediments are more marine to the west and south. A computer generated map of kaolin thickness (Fig. 16) compared with a structure contour map of the top of the Clayton Formation suggests kaolin thickness may be related to the topography ofthe basin's floor (Cofer and Manker, 1983).
Development of at least two bauxite horizons and dessication cracks in the kaolin also are indicative of subaerial exriosure. Rare, carbonized and pyritized plant remains, casts or molds of burrows, and organic-rich clay lenses found in pure kaolin with palynomorphs suggestive of a fresh-water environment are thought to represent paleo-soi Is and fresh-water swamps (Cofer and Fredericksen, 1982; Cofer and Manker, 1983).
7/isc;r/toma Formation (Ttu)
Various sediments are defined as belonging to the Tuscahoma Formation in the current map area (Cofer and Manker, 198J; Owen, 1963, Zapp, 1965). Owen included all sediments beneath the Claiborne Group and overlying the Clayton Formation. Based on Cofer and Manker's description of the Tuscahoma Formation, beds in the lower part of this unit appear similar to those included in the Nanafalia Formation in this study.
The Tuscahoma Formation observed in the current study consists of non-fossiliferous, inter-laminated clay, silty clay, and line quartzose sand. Fish teeth, foraminiferal tests and glaconite pellets were noted by Cofer and Manker ( 1983 ). The 11pper portions of the Tuscahoma are commonly rusty orange to rusty tan, whereas the lower portions are mainly dc.rk gray (Fig. 17, 18, 19, 20, 21 ). The contact between the different colored parts may be conformable to the contac;s or convoluted (Figs. 17, 18, 19, 20, 21). This color change may reflect a paleo oxidizing-reducing front perhaps resulting from ground water or surface weathering. Where observed in the open-pit mines in the Andersonvill::: bauxite district, the lower contact of the Tuscahoma Formation with the Nanafalia Formation (Figs. 6, 7, 8, II, 18, 19, 21) appears conformable. Descriptions of the Tuscahoma Formation from the Wilburn Mine by Cofer and Manker (1983) suggest that channeling by the Tuscahoma Formation cuts into the Nanafalia Formation. These expvsures could not be examined during the present study, as the Wilburn Mine has been reclaimed. This discrepancy may result from different definitions of the Tuscahoma Formation. The upper contact with the Claiborne Group is generally also conformable as observed in the open-pit mines in the Andersonville bauxite district (Figs. 6, 7, II, 18, 19, 20, 21), but is locally cut by channels at the base of the Claiborne Group (Fig. 27) or completely J\.:moved (Figs. 22, 26, 28). Occasionally, seeps mark the contact of the impermeable Tuscahoma Formation and the permeable Claiborne Group sandstone.
Most of the exposures of the Tuscahoma Formation are found in the open-pit mines in the Andersonville bauxite district or on slopes adjacent to the Sweetwater and Toteover Creeks and Flint River (Fig. 20). Otherwise, exposures of the Tuscahoma Formation are generally absent in the current map area. Thickness of the Tuscahoma Formation 011 the cross-sections in Plate 4 ranges from 0 to 5 feet in the northern part of the Andersonville and Pennington quadrangles from I0 to approximately 15 feet in the Methvins quadrangle. Northward thinning of the Tuscahoma Fonnation may be related to original depositional thickness and/or erosion prior to Claiborne Group sedimentatior,.
Reinhardt and others (1994) describe the Tuscahoma Formation as composed of l 0 to 60 feet of dark greenishgray clay and silt inter-laminated with thin, medium greenish gray, quartz sand beds . The basal bed consists of massive clayey, fine to medium -grained sand containing coarse quartz, glauconite and phosphate pebbles.
Sedimentological analysis of the Tuscahoma Formation suggests a very low energy environment of deposition for the silts and clays. Abundant siliceous dinoflagellate tests to the south and fern spores in the central and northern parts of the district suggest a seaward to shoreward transitional environment (Cofer and Manker, 1983). In the lower portion of the Tuscahoma Formation, coarser-grained sediments and cross-bedding may indicate a fluvial-deltaic environment. This lower portion of the Tuscahoma Formation as defined by Cofer and Manker ( 1983) may be the equivalent sediments considered to be the upper part of the Nanafalia Formation in the present study.
9

Hacltetigbee Formation - Bashi Marl Member
The Bashi Marl Member has not been recognized in the surface mapping of the current quadrangles or in drill hole logs. A glauconitic limestone at the base of the Claibome Group that was logged in several of the drill holes in or adjacent tc the current map area may be the equivalent of the Bashi Marl but has not been recognized as that unit. Marsalis rmd Friddell ( 1975) found the Bashi Marl to be di scontinuous along the Chattahoochee River, and Davis ( 1974) sugge~ted that this unit, as well as the Hachetigbee Formation was both discontinuous and a difficult unit to differentiate from the enclosing sedimentary units .
Reinhardt and others ( 1994) describe the Hatchetigbee Formation as generally less than 25 feet of light to dark greenish-gray, dominantly massive, well-sotted, very fine- to fine-grained quartz and glauconite sand. This unit contains intervals of interbedded and inter-laminated clay, sil t and very fine quartz sand.
Lower to Middle Eocene
Claiborne Group (Tcb)
The Claiborne Group is a thick, generally sandy unit, which, in much of the current map area, lies between th e Tuscahoma Formation and the Altamaha Formation and/o r the Tertiary Sediments and Residuum unit. In the northern part of the Andersonville and Pennington quadrangles, the Tuscahoma Formation thins to zero thickness and/or is e'rodcd prior to Claiborne deposition. Where the Tuscahoma is missing, the Claiborne Group lies directly on top of the Nanafalia Formation . Weathered outcrops of the sandy portions of these two map units may be indistinguishable from each other making mapping in th ese areas more difficult.
In most of the current map area, the Claiborne Group appears to consist principally of the Tallahatta Formation as shown ,)n the Geologic Map of Georgia (Georgia Geologic Survey, 1976). Sandy sediments in this stratigraphic interval that <ire found in this part of Georgia's Coastal Plain have normally been referred to as the Tallahatta Formation (Marsalis and Friddell, 1975; Luckett, 1979; Owen, 1956). These sediments are equivalent to those sandy sediments classified as the Claiborne Group in the Bronwood, Neyami, Smithville East and Smithville West quadrangles (Summerour, 2000), in the Bottsford, Dawson, Parrott and Shellman quadrangles (Cocker, 200 I), and in the Americtls, Lake Collins, Plains and Preston quadrangl es (Cocker, 2002).
Furth~r to the east, sediments in this stratigraphic interval are referred to as the Perry, Lisbon and Congaree Formations (Hetrick, 1994; Huddlestun and Summerour, 1996; Summerour, 1999, 2000). Comparison of exceptional, piJssibl y complete, exposures of this unit, particularly in the Parrott quadrangle (Cocker, 2001) and in the mine exposures in the Andersonville and Pennington quadrangles, with exposures and descriptions of the Perry and Cong~1ree Formations do not appear to support stratig1aphic distinction of the Perry and Congaree Formations from the Tallahatta Formation. Variations in grain si ze, sediment composition, bedding features and clasts may be related to loc;d variations in depositional environment and to weathering history. The Perry Formation is believed to represent the up dip sandy equivalent of the more calcareo us Lisbon Formation. The Perry Formation and/or sandy Lisbon FOi'l11<ltion are indistinguishable from the Tallahatta Formation. In the drill hole GGS # 137, located near the eastern edge of the Methvins quadrangle, marl of th e Lisbon Formation, as well as an overlying interval of Ocala Limestone; <lre in the same stratigraphic interval mapped as sandy Claiborne Group. As neither calcareous unit was observed at the surface in the Methvins quadrangle, the stratigraphy of that drill hole could not be directly correlated with the current surface mapping. In this project report and on the project geologic maps and cross-sections (Plates I - 4), this sltatigraphic interval is treated as the Claiborne Group and subdivided where intersected in the drill hol es (GGS # 137 and GGS #298) in Plate 4). A more in-d epth treatment of the Claiborne Group stratigraphy is beyond the scope ofth is mapping project.
Where exposed in the current map area, the Claiborne Group consists generally of massive to finely laminated , locally strongly cross-bedded, white to light tan to brick red, locally kaolinitic, fine- to coarse-grained sand and sandstone (Figs. 6, 7, 11 , 18, 19, 21, 22, 23, 25, 26 , 27, 29). Locally, clasts of kaolin, presumably derived from erosion or the underlying Nanafalia Formation, may be common in the lower pottions of the Claiborne Group (Fig. 24). Exclusi1.e of mine exposures, most exposures of th e Claiborne Group in the Andersonville, Methvins and Pennington quadrangles are rather nondistinct and are generally subject to erosion . The upper portions of the Claiborne Gruup may appear massive and brick red and superficially similar to the overlying Altamaha Formation . Ground vvatcr has locally stained the cross-bedded , white sandstones to various shades of yellow and red. The Claiborne Group is best exposed within the current map area in open-pit mines in the Andersonville bauxite district.
Thickness of the Claiborne Group, from the cross-sections in Plate 4, may range from 50 to approximately 175
10

feet. This unit may be thinner where eroded prior to Altamaha sedimentation and is locally much thicker where the Claiborne Group sands cut into the underlying stratigraphic units (Fig. 22). Although surface mapping suggested local thickening or thinning of the Claiborne Group , no direct evidence was available until numerous channels were observed in the open-pit mines in the Andersonville bauxite district (Fig. 22 ).
Outcrops of the Claiborne Group are most commonly of low relief and generally consist of light tan to buff colored, poorly indurated sand . In intertluve areas where the Claiborne Group is exposed, relief is so poorly developed that no outcrops are present. Presence of th e Claiborne Group may be determined by extensive stretches of light tan, sandy roads and farm fields. Bedding and sedimentary structures that may be visible in fresh, more indurated Claiborne Group sandstone are obliterated durin g weathering. The number and extent, as well as quality of exposures generally increases along roads which descend into the stream valleys. One of the most consistentl y developed outcrop characteristics of the Cl aiborne Group sands are the vertical striations developed on surfaces exposed to descending surface waters- most probably rainwater. These striations are best developed on finer grained sediments, but are more or Jess developed on coarser grained sands as well. While useful in areas high in the stratigraphic section, poorly cemented sandstones lower in the section (portions of the Nanafali a Formation) may also display vertical striations.
In addition to the physical degradation of outcrops, the Claiborne Group sandstones are highly susceptible to eroswn. Erosion of relatively less indurated portions of the Claiborne Group sandstones commonly leads to undercutting and eventual collapse of outcrops (Figs. 29 , 30, 31 ). Erosion of the soft sands that constitute the deeply weathered portions of the Claiborne Group is of major concern to the farmers in the area, particularly on slopes adjacent to a lnajor drainage. Erosion can be swift and devastating to a fanner's field. Most of the slopes adjacent to the streams have been kept in a natural, forested state to curb that type of erosion.
Contacts between the sandstones of the Claiborne Group and the overlying Altamaha Formation may be identified by 3tcep, gullied slopes in the Claiborne Group sandstone changing abruptly upward to more gentle slopes of the more indurated, argillaceous Altamaha sandstone (Figs. 29, 30, 31 ). Defining the extent and thickness is dependent on locating and identifying contacts . Rarely are contacts as neat and well defined as the contact in Figure 30. Usually, they can only be found through careful inspection of weathered outcrops. A thin line of ironstone pebbles and iron oxide cl asts at the base of the Altamaha Formation defines the contact in Figure 30. Weathering characteristics (Figs. 29, 30) are also important for defining contacts. Channeled water flow as in road drainage ditches \Viii commonly produce potholes where the top of the Claiborne Group sandstone is exposed beneath a relatively harder, protective rock unit.
In previuusly mapped quadrangles, high concentrations of generally hard-cemented, black iron oxides were found within the Claiborne Group sands beneath the contact with the overlying Altamaha Formation or the Te1iiary Sediments and Residuum unit (Cocker, 200 l, 2002). The presence of these iron oxide crusts in the current map area is minimal:
Sedimentological analysis of the Claiborne Group suggest a quiet, shallow-water marine deltaic or neritic environment (Cofer and Manker, 1983). Dip directions of cross-bedding foresets from the lower part of the Claiborne Group may indicate a dominant northeasterly trending longshore current and a lesser tidal influence in west and south east directions. Sands are dominantly angular to subangular qua1iz, whereas silts and clays are mainly kaolin with lesser amounts of quartz.
Lisbon Formation (Tl)
The Lisbon Formation has not been observed as a di stinctly identifiable unit in outcrops in the map area but has been noted in clri II holes in the easternmost part of the Methvins quadrangle. As was noted in the above section, the Lisbon Formation in the drill holes could not be mapped on the surface in the Methvin s quadrangl e (Plate 3) but was included in the cross-section in Plate 4.
This unit is represented by yellowish-gray to white, glauconitic, micritic, clayey, finely sandy, soft to variably indurated limestone, and bluish-gray, sandy, calcareous clay (Luckett, 1979; Owen, 1963; Summerour, 1999) in the Drayton and Bronwood quadrangles to the east and south of the current map area. Outcrops of a bluish gray, sandy silt or sandstone found in the Dawson quadrangle were assigned to the Tertiary Sediments and Residuum unit (Cocker, 200 I). Clasts of a bluish gray, sandy silt or sandstone which were found in an unusual conglomerate in the Americus quadrangle, have been assigned to the Tertiary Sediments and Residuum unit, and may be derived from the Lisbon Formation.
ll

Upper Eocene
Sediments of the Upper Eocene Clinchfield Formation and the Ocala Group, which occur in the Neyami and Bronwood quadrangles to the south, were not found or recognized in the present map area with the exception of a short interval of possibly Ocala Group limestone near the top of drill hole GGS # 137 in the easternmost part of the Methv ins quadrangle (Plate 4). In that drill hole , the Ocala Limestone consists of 26 feet of creamy, glauconitic, sandy, fossiliferous limestone (Herrick, 1961). Fossils consist of macroshells and the foramenifera Lepidocyclina Most of these sediments have probably been removed by erosion prior to Miocene sedimentation in the present map area. Otherwise, they may be included as undifferentiated residuum in the Tertiary Sediments and Residuum map unit.
Eocene to Oligocene
Tertiary Sediments and Residuum (Tsr)
In or adjac ent to the current map area, all sediments above the Claiborne Group have been referred to as residuum of Lisbon and Ocala limestones (Cofer and Manker, 1983 and Zapp, 1965). These sediments are distinguishable as both residuum and overlying Miocene age Altamaha Formation (Cocker, 2001, 2002 and Summerour, 1999, 2000). Sediments belonging to this unit are generally poorly exposed and appear to be rather limited in their distribution.
Sediments assigned to this unit may consist of massive chert, chert rubble in predominantly maroon to brown to chocolate brown plastic or sticky clay, sandy clay, and sandstone (Fig. 32). The clays may be Jess commonly white and orange. Chert-bearing outcrops or exposures were less abundant than in previously mapped quadrangles to the west and south and east (Cocker, 2001, 2002 and Summerour, 1999, 2000). Chert and clays that are the most abundant part of this unit may be derived from intense, subaerial weathering of carbonate sediments. An unusual, white to light tan, quartz pebble rich sandstone found in the southwestern part of the Pennington quadrangle is assigned to this unit as it lies beneath a contact with the Altamaha Formation and does not resemble any older lithologies (Figs. 33, 34, 35). In addition, numerous iron stained fractures cut this unit but are absent in the Altamaha Formation (Figs. 34, 35).
In the current map area, outcrops and exposures of residual clay and chert are spatially enclosed within the
Altamaha rol mat ion or between the Altamaha Formation and the underlying Claiborne Group sandstone (Plates 1-
4). Outcrops that display contacts between the Altamaha Formation and the underlying Claiborne Group (Figs. 6, 22, 27, 29, 30, 31, 38, 40), as well as geologic mapping indicate the discontinuous nature of the Tertiary Sediments and Residuum unit. Because relief is generally less in the Methvins quadrangle than in the Andersonville and Pennington quadrangles, the overall distribution of this unit is difficult to assess. Mapping in the other quadrangles (Cocker, 200 I, 2002 and Summerour, 1999, 2000) suggest that more exposures of this unit would be seen in the Methvins quadrangle. Thickness of the residuum unit is quite variable, because it is derived through weathering and erosion of rock units prior to Altamaha sedimentation. Where observed in the current map area, thickness of this unit is on the ,)rder of 5 to I0 feet (Figs. 32, 34, 35).
Some of the more resistant portions of the Tertiary Sediments and Residuum unit or erosional remnants, may be preserved as islands or knobs that may represent paleo-islands or knobs at the time of Altamaha Formation deposition, Sediments belonging to the Altamaha Formation may overlie or occur laterally adjacent to these islands (Plates 1 - 4). In the vicinity of these islands or knobs, the basal conglomerate of the Altamaha Formation contains more abundant, angular chert or clay clasts derived from the island, as well as rounded ironstone pebbles commonly found in abundance in the basal conglomerate (Figs. 36, 37).
Chert found in the map area ranges in size from gravel to cobbles and boulders. More massive chert is occasionally found. Isolated chert clasts are most commonly found associated with Altamah a Formation sediments and may be sedimentary clasts eroded from the residuum and incorporated into the Altamaha Formation during deposition of the Altamaha Formation. Concentrations of chert clasts associated with the sticky, brownish clay are generally 1ilapped as residuum rather than Altamaha Formation.
Fossils preserved within the chert-bearing resid uum have been identified as Early Oligocene (Summerour, 2000) or Latl.! Oligocene (1-Iuddlestun and others, 1974). Stratigraphic position of the residuum is permissible for Early or Late Oligocene, as well as including rocks of Middle to Upper Eocene age. Early Oligocene residuum may be derived from weathering of the Oligocene Tivola or Ocala Limestone (Summerour, 2000). Late Oligocene res iduum may be derived from the Suwanee Limestone. Chert-bearing residuum could also be derived from the Lisbon Fmmalion (Huddlestun and others, I974; Zapp, 1965), another stratigraphically permissible source unit for
12

the residuum in the current map area. Huddlestun and others (1974) distinguished the occurrence of chert as clasts and in situ massive chert in a
similar manner to that which occurs in the current map area. Chert clasts are described as sand to gravel-size detritus, cobbles and boulders in a matrix of sand and clay. In situ chert occurs as massive, bedded chert, and chert pinnacles surrounded and overlain by Neogene age sands, clays and gravels. These in situ cherts are referred to as the Flint River Formation by Pickering (1966, 1970).
In previous STATEMAP mapping (Summerour, 1999, 2000) and the adjacent Fort Valley geologic atlas (Hetrick, 1990), the Terti ary Sediments and Residuum unit (Tsr) has included mottled, variably waxy to sandy clay or clayey san:l with scattered in situ(?) masses of fossiliferous chert, chert float, plinthite, and ironstone. Geologic observations in the current map area as well as observations by Huddlestun and others ( 1974) and Pickering ( 1966, 1970) indicate that this residuum consists of a chert-clay residue. Plinthite is generally formed in the iron-aluminum rich, clayey subsoils of the Altamaha Formation, and has not been observed in the Tertiary Sediments and Residuum unit. Ironstone is present as pebbles within the Altamaha Formation, as crusts near the top of the Claiborne Group sediments, and as crusts incorporated in conglomerates within the Altamaha Formation . Also, generally isolated occurrences of chert clasts in sandstone or argillaceous sandstone are interpreted as being within the Altamaha Formation. Chert float and chert collected for rock gardens and walls should be viewed with caution, as they may be derived from the Tertiary Sediments and Residuum unit or the Altamaha Formation.
Miocene
Altamall11 Formation (Ta)
Clastic sedimentary rocks of the Altamaha Formation are the youngest Tertiary rocks in the map area and are generally found at the higher elevations, particularl y on the broad intertluve areas (Plates I - 4). Locally, the Altamaha Formation is present at lower elevations than the projected lower contact of the Altamaha Formation on top of the internuve areas. At higher elevations the Altamaha Formation is in contact with the Tertiary Sediments and Residuum unit (Figs. 32, 34, 35) and the Claiborne Group (Figs. 6, 22, 27, 29, 30, 31, 38, 40). At lower elevations. t! , Altamaha Formation is found cutting through the Claiborne Group to the Tuscahoma Formation (Figs. 38, 39) and Nanafalia Formations (Figs. 40, 41). Elevation differences in the lower Altamaha contact, as well as cutting progressively older sedimentary units to the north and west indicate a major disconformity prior to (and perhaps during) Altamaha sedimentation. Active channeling occurred during Altamaha Formation deposition (Fig. 27). In many in stances, the presence of the Altamaha Formation at progress ively lower elevations coincides with a present drainage. Thickness of the Altamaha Formation is also quite variable. Maximum thickness depicted on the cross-section~; (Plate 4) is about 40 feet. Average thickness is probably on the order of 20 to 30 feet. Although the Altamaha Formation is rather thin on the upland surfaces, indurated sandstones of the Altamaha Formation have protected sands of the underlying Claiborne Group from more rapid erosion . Stream valleys are rather small and shallow '~her~ they are sti II in the Altamaha Formation or j kiSt recently cut through as in the southwestern part of the Andersonville quadrangle and over most of the Methvins quadrangle (Plates l, 3 and 4). Where larger stream valleys have cut through the Altamaha Formation, downcutting appears to have been rapid with steep slopes, particularly in the soft ~laiborne Group sandstones in much of the Andersonville and Pennington quadrangles and in the northeastern part of the Methvins quadrangle (Plates I - 4).
Lithologically, the Altamaha Formation consists of sandstones, clayey sandstones, and conglomerates. The dominant lithology observed in the current map area is a massive, brick-red, argillaceous, fine-grained to gritty sandstone (Figs. 6, 27, 29, 40, 41 ). Massive, more or less mottled, clayey sandstones may be found beneath the sandstone. Conglomerates are commonly found at or neat the base of the Altamaha Formation. Most clasts are rounded iron~.tone pebbles, but may locally include more angular to subround iron oxide crusts, iron oxide-cemented crusts and abundant chert. In a few instances, source rocks for the more angular clasts are very close. An outcrop close to outcrops of clay and shale of the Tertiary Sediments and Residuum unit contains interbedded conglomerates with di stinctly different clast populations. One conglomerate contains rounded ironstone pebbl es and the other contains angular to subangular shale clasts, probably derived from the nearby Tertiary Sediments and Residuum unit (Figs. 36, 370. Occasionally, cross-bedding is observable in the sandier portions of the Altamaha Formation. Weathering, iron staining and mottling probably mask the presence of more sedimentary structures and textures in the Altamaha Formation (Cocker, 2002).
Altamaha Formation sandstones contain variable amounts of ironstone pebbles that generally range in size from 0.25 to 1.00 inches (Figs . 30, 35, 36, 37, 38, 39). Occasionally, ironstone pebbles up to 2 inches are found . Most ironstone pebbles are black and appear to be round to subround with an apparent polish. Visual inspection with a
13

hand lens suggests that these pebbles consist of clastic quartz grains cemented by a mixture of iron oxides, quartz and perhaps hardened clay. These pebbles have been referred to as pi inthite (Summerour, 2000); however, true plinthite is acti.tally a soft, weathering-related segregation of iron oxide to form irregularly shaped masses (Brady and Wei!. 1999). Plinthite may be found locally developed as irregular-shaped masses in the lower portions of the kandic weathering zone. These ironstone pebbles are clastic in their occurrence as indicated by their common occurrence in discrete layers. Generally found dispersed in a san dstone or argillaceous sandstone matrix, these ironstone peL'bles are also concentrated in conglomeratic portions of the Altamaha Formation and occasionally in distinctly layered portions of the Altamaha Formation. Estimated abundance of the ironstone pebbles in the Altam aha Formation in the current map area ranges from 0 to 50% with the most commonly found concentration estimated in the 5 to l0% range. Weathering of the iron stone pebble-bearing Altamaha Formation concentrates these pebbles as a l<1g deposit on the present surface . Although these ironstone pebbles have been noted from this part of the stratigraphic section over much of the Upper Coastal Plain of Georgia, no source for the ironstone pebbles has been suggested .
Generally less abundant pebbles consist of quartz, quartzite, biotite gneiss/granite, chert, sandstone and shale. Occurrences <J f' abundant quartz pebbles such as those noted in the Bottsford quadrangle (Cocker, 2001) were not as common or noteworthy in the present map area. A few shale clast conglomerates are also present but are difficult to recognize (Figs. 38, 39, 41 ). These conglomerates can easily be mistaken for mottled argillaceous sandstone especially when they are present in that portion of the soil/weathering zone.
Argillaceous sandstone is generally mottled with various shades of white, yellow and red being the most prevalent. Wltcre present with sandier portions of the Altamaha Formation, this mottled clay-rich lithology is always beneath the sandier portion. Although relatively indurated, this clay-rich lithology is believed to be the kandic zon e formed by downward mobi Iization of clay. The amount of clay seems to be variabl e throughout the current map area. When compared with other mapped quadrangles, the amount of mottled argillaceous sandstone in the current map area is relatively minor. Data from Long and Baldwin (1915) indicate that, despite the enrichment of clays in the subsoils (kandic zone), the rock/soil is an argillaceous sandstone based on a greater volume of sands versus silts and clays. Mnttling is believed to represent oxidation and remobilization of iron by ground water during weathering. Occasionally concentration and precipitation of iron resulted in the formation of black masses that are called plinthite. Ironstone pebbles described above may also occur in the more argillaceous portions of the Altamaha Formation.
Size analyses and desc riptions of soil and subsoil for Grady sandy loam, Greenville sandy loam, Ruston sandy loam, and Ti(ton sa ndy loam soils in Terrell County (Long and Baldwin, 1915) suggest that these soils were derived from the Altamaha Formation (Cocker, 2001). These four soil types have the same grain size distribution in the soil and subsoil. Subsoils show a second population of clsy-size patticles that reflect enrichment of clay in the subsurf<1cc Th e upper soil zone corresponds to the more uniformly colored massive sandstone. The lower clayey zone corn:sponcls to the lower mottled argillaceous sandstone (Cocker, 200 I).
High angle jointing, that was noted in the more argillaceous lithologies of the Altamaha Formation during previous yea1 s' mapping (Cocker, 200 I), is rather rare in the Andersonvi lie, Methvins and Pennington quadrangles. These joints are accentuated by bleaching of approximately 2 to 6 inches of the adjoining rock probably by oxidizing ground water moving along the joints. Some iron oxide deposition occurred on the outer fringes of these bleached joint envelopes. These joints have not been observed in the overlying sandier portions of the Altamaha Formation, a11cl observable displacement is lacking or only on the order of a few inches. As there was no limestone directly bcnesth the Altamaha Formation in this area due to weathering and erosion (see Tertiary Sediments and Residuum L:nit description), subsurface dissolution of underlying Eocene and Oligocene carbonate rocks (Summerou1, 2000) may not be a viable cause for the observed jointing.
Deposition<1\ environment of the Altamaha Formation is interpreted as an irregular, prograding fluvial and estuarine syste111 developed during the Early and Middle Miocene period of lowered sea level (Huddlestun, 1988, 1993). Prior to and during the Early and Middle Miocene, Oligocene and older sediments were exposed to intensive we<1thering and erosion . As a result, the lower contact of the Altamaha Formation with underlying units is highly irregular. Olcler units exposed to the weathering and erosion may be irregular in thickness or missing.
Detailed 111apping of the Altamaha Formation in South Carolina in and near the Savannah River Site (Fallaw and Price, I992; Nystrom and Willoughby, 1982) shows similar lithologies and geologic relations as those found in the prese nt ma p area. The Altamaha Formation, also locally referred to as the "Upland Unit", is described as red, purple, gray, orange, yellow, and tan, poorly sorted, clayey and silty, fine to coarse sands, with lenses and layers of gravel s, pebbly sands, and oxidized, massive clays. Clay clasts are abundant. Cross-bedding is prominent in places, and muscovi,~ and flecks of weathered feldspar are locally abundant. Clay-filled fissures, probably caused by weathering, are numerou s in places. Within the Savannah River Site (SRS), the Altamaha Formation occurs on the
14

surface and at higher elevations, but is also missing in some higher elevation SRS wells. It is up to 70 feet thick in parts of the SRS. The lower surface of the unit is very irregular because of erosion of underlying deposits prior to deposition ofthe Altamaha Formation (Fallaw and Price, 1992; Nystrom and Willoughby, 1982).
Tertiary- Quaternary
Tertiary- Quatemwy Alluvium (TQal)
In the Pennington quadrangle and adjacent parts of the Byromville quadrangle, broad flat areas (Fig. 43) at elevations of approximately 290 to 300 feet and 315 to 340 feet on slopes adjacent to the Flint River (Plate 2) have been described as former river terraces of the Flint River (Hetrick, 1996, Reinhardt and others, 1994, Summerour, 1999, and Zapp, 1965). Aside from being relatively flat and adjacent to a major river, no distinctive exposures of river terr<Jce deposits were found in the Pennington or Byromville quadrangles. Fine- to coarse-grained sand in plowed fields on these terraces is indistinguishable from underlying sand of the Claiborne Group and Nanafalia Formation. A series of shallow core holes (Fig. 4) drilled in March- May, 2003 were designed to investigate the nature of the material in these terraces in the Pennington, Byromville and Drayton quadrangles. With the exception of one drill hole in the Drayton quadrangle, sediments in the other drill holes were similar to the mapped or projected underlying geologic unit (core descriptions in Appendix). These large flat areas could be erosional terraces, cut into the underlying soft Tettiary sediments by the meandering Flint River. As no positive evidence for fluvial deposits that are younger than the Miocene Altamaha Formation or older than the alluvial deposits found directly associated with the Flint River, i.e. Quaternary Alluvium and Quaternary Alluvium 2, a fluvial, erosional origin is suggested for the terraces in the Pennington quadrangle and adjacent parts of the Byromville quadrangle.
A more detailed examination may locate unequivocal terrace deposits in these quadrangles, as some evidence in the Drayton quadrangle indicates that some terrace deposits are present there. A re-examination of the Drayton quadrangle located several exposures of gravel and gravel plus sand that are distinctly different from exposures in other terraces that were mapped and drilled in the Pennington, Byromvi lie and Drayton quadrangles. Because the gravel lies on the top of outcrops of the Altamaha Formation and is lithologically distinct from other gravels found within the Altamaha Formation, these gravels may represent remnants of a fluvial terrace deposit. These gravels consist of large, commonly oblong quartz, quartzite, and biotite plus hornblende gneiss (Fig. 42). The extent of these gravels is very limited, however. As these gravels lie on top of the Miocene Altamaha Formation, they are considered to be younger than the Altamaha Formation. These gravel deposits are also approximately 70 to I00 feet higher in :levation than the Quaternary Alluvium 2 terrace that lies within the current Flint River valley and are considered to be older than the Quaternary Alluvium 2 deposits.
Quaternary to Recent
QuaterntiiJ' Alluvium 2 (Qal 2)
Remnants of the most recent terrace, above the current flood plain, ranges from approximately 250 feet in elevation in Ihe southern part of the Pennington quadrangle to approximately 280 feet in the northern part of that quadrangle. This alluvium was mapped as underlying topographically higher flat areas than the Quaternary Alluvium (Qal) but was well confined by steep valley walls of the Flint River valley.
Quatemary Alluvium (Qal)
Alluvium was mapped as occupying the basal, generally flatter portions of creek valleys in the map area. Alluvium was mapped as extending up the smaller tributaries where a stream occupied the valley and the valley could be recognized as a valley on the topographic map. Except for minor exposures along stream banks, no outcrops were observed. The few exposures suggest that the alluvium in the current map area is similar to that described by Hetrick (1990) and Summerour ( 1999, 2000). Alluvium is described as consisting of variably micaceous, p::Jorly-sorted sand, clayey sand, and clayey silt, with a minor amount of quartz and local chert gravel, and variable amounts of organic matter. Large expanses of swampy areas in the Flint River valley suggest a greater portion of organic matter may be present there than other alluvium. Thickness of alluvium is variable and is probably greater in the Flint River valley and valleys of its major tributaries, i.e. Sweetwater, Camp, Triple, and Mountain Creeks.
Several peat beds formerly exposed in the Wilbum Mine, located on the north side of Sweetwater Creek, were
15

sampled ilx c,Jrbon-14 age analysis (Cofer and Manker, 1983. Age determinations, from bottom to top of a 13.5 foot section, were 21,300 +/- 400 yBP, 15, 840 +/- 300 yBP, and 10,570 +/- 250 yBP. As these peat deposits were north of the Andersonville Fault and were lower than the present valley floor, Cofer and Manker suggest the peat accumulated in a reactivated fault-dammed basin. It is unclear if these deposits represent sediments of the Quaternary Alluvium or are equivalent in age to the Quatemary Alluvium 2 deposits.
Alteration of primary sedimentary textures
Based on observations and examples from the previous years' mapping (Cocker, 200 I, 2002), primary sedimentary structures in many Coastal Plain clastic sediments have been obliterated by red , yellow and brown staining and mottling related to deposition of iron oxides and clays by ground water. Primary sedimentary structures were probably more widespread than can be observed today. Several episodes and types of alteration of the Coastal Plain sedimenls have occurred since their deposition.
Correlation of STATE MAP map units with earlier geologic maps
Differences between the Americus I: I 00,000 scale geologic map (Reinhardt and others, 1994) and the Butler geologic <~lias (Hetrick, 1996) with the Andersonville, Methvins and Pennington quadrangles (Fig. 2, Plates 1 - 3) are due, ill part, to differences in stratigraphic definitions, map units delineated, and the presence of lithologies previously un1ecognized and unmapped by Reinhardt anc;J others (I 994) and Hetrick ( 1996). Table 2 shows the STATEM.\P :;rratigraphic terminology compared with the terminology of Reinhardt and others ( 1994).
The principal difference between the present mapping and that of Reinhardt and others ( 1994) is that the stratigraphy above the Lower Eocene Hatchetigbee Formation, except for alluvium, was not subdivided in the Americus 30' x 60' quadrangle map. All younger sediments are included in the "Tallahatta Formation and younger Paleogene deposits, undivided (Oligocene? - lower Eocene)" (Tta) unit by Reinhardt and others (1994). This suggests that; Reinhardt and others (1994) did not recognize Miocene age sediments or did not have the time to delineate the younger stratigraphy. This map unit (Tta) is equivalent to the four Middle Eocene through Miocene stratigraphic units in the current study area (Fig. 5, Plates I - 3) and on the geologic cross-sections (Plate 4). Comparisons ol' mapped contacts from the Butler atlas and the Americus 30' x 60' quadrangle map with the present maps of ihe Andersonville, Methvins and Pennington quadrangles are, in general, relatively similar. Contact comparisons were achieved by plotting a scanned version of the Americus 1: I 00000 scale map overlain by the current mapping.
On the I :500,000 scale Geologic Map of Georgia (Georgia Geologic Survey, 1976) the map units which lie within the curient map area are the Clayton (Pel), Nanafalia (Pnf), and Tuscahoma Formations (Ptu), Claiborne undifferentiated (Ec), Eocene and Oligocene residuum ~111differentiated (Eo-M), and Quaternary alluvium (Qal). Geologic unils on the Geologic Map of Georgia (Georgia Geologic Survey, 1976) that occur in bottoms of the Sweetwater and Camp Creek valleys are mislabeled as Tuscahoma Formation (Ptu). These units are stratigraphically below the Nanafalia Formation and were mapped as Clayton Formation (Zapp, 1965). A plot ofthe Digital Geologic Map of Georgia (Cocker, 1999a) relative to the currently mapped geology of the Andersonville, Methvins and Pennington quadrangles illustrates a relatively good agreement of the two sets of maps. The principal differences lie in the mappi11g of Quaternary alluvium in stream valleys and the mapping of the Altamaha Formation (Ta) and Tertiary Sediments and Residuum (Tsr) generally in the stratigraphic position of the Eocene and Oligocene residuum undifferentiated (Eo-M) on the Digital Geologic Map of Georgia (Cocker, 1999a). Spatial differences are related to the reconnaissance scale mapping that produced the Geologic Map of Georgia (Georgia Geologic Survey, 1976), stretching the usable scale of the Digital Geologic Map of Georgia (Cocker, 1999a) to that of the 7.5 minute quadrangles, and to errors created during production of the Digital Geologic Map of Georgia (Cocker, 1999a).
Current mapping was compared with the Geologic ALias of the Butler Area (Hetrick, 1996) which adjoins the current map area along the northern and western edge of the Andersonville quadrangle and the northern edge of the Pennington quadrangle. In the Butler Atlas, all of the Paleocene to Middle Eocene sedimentary units were combined into an undifferentiated map unit, i.e. Paleocene-Middle Eocene Clayton Formation- Wilcox Group-Claiborne Group undifferentia<ed (Hetrick, 1996). Younger sediments were also combined into one map unit, i.e. post Lower Eocene sediments an'd residuum undifferentiated. The early Tertiary - post Lower Eocene sediments contact is similar on the Butler ALias with the present mapping on the western edge of the Andersonville quadrangle. Correlation of contacts is lacking along the northern edge of the Andersonvi lie and Pennington quadrangles, in part because of the lack of detail regarding the Tertiary stratigraphy on the Butler Atlas. The Providence Formation was also mapped in the Camp Creek valley on the Butler Atlas, but has been mapped as the Nanafalia and Clayton Formations (this
16

report and Z::1pp, 1965). Because o~ generally similar definitions of the stratigraphic units and the detail of the mapping, correlation of
the present mapping with that of Zapp ( 1965) is relatively good. The primary difference in map units concerns sediments above the Claiborne Formation, which were mapped as residuum of Eocene and 01 igocene limestones but have been subdivided into an underlying residuum and the younger, Miocene-age Altamaha Formation. A GIS coverage was created by scanning a paper copy ofZapp's map, and then tracing and editing the contacts in Arc Edit. That coverage was overlain with the present study's mapped exposures. Many of the mapped exposures and contacts coincide with the geology mapped by Zapp. Because of the numerous (I, I00) exploration dri II holes that were focused 01: the upper and lower contacts of the Nanafalia Formation, and general lack of exposures of these contacts other than in the mines, the lower contacts of the Altamaha Formation (this study) coincide with the lower contact of the residuum of' the Jackson Group and Oligocene limestone (Zapp, 1965).

TABLE 2. Comparison of STATE MAP stratigraphic terminology with that of the Americus geologic map of Reinhardt and others (1994).

STATEMAP Project stratigraphic terminology (current map area) (TQal) Tcrti~11")'- Quaternary Alluvium
(Ta) Miocenc: AItam aha Formation (Tsr) Teniary Sediments and Residuum (TI) Middle Eocene Lisbon Formation (Tcb) Middle Eocene Claiborne Group - Tallahatta Formation/Perry Formation

Americus 1:100,000 geologic map of Reinhardt and others (1994) (QTI) Deposits of low alluvial terraces (Pleistocene and Holocene)
(Tta) Te1tiary Tallahatta Formation and younger Paleogene deposits, undivided (Oligocene?- lower Eocene).

(Ttu) Upper Paleocene Tuscahoma Formation (Tn) Upper Pnleocene Nanafalia Formation
(Tel) Lower Paleocene Clayton Formation (Kp) Upper Cretaceous Providence Formation

(Ttu) Upper Paleocene Tuscahoma Formation (Tn) Upper Paleocene Baker Hill and Nanafalia Formations (Tc) Lower Paleocene Clayton Formation
(Kp) Upper Cretaceous Providence Formation

~rr

BIOSTRATIGRAPHY

Most outcrops in the present map area were nonfossi li ferous in terms of macrofossi Is. Chert residuum is locally fossiliferous in the map area. Summerour (2000) documents the presence of possible, poorly preserved, Late Eocene fossils and Early Oligocene fossils in fossiliferous chert. It is unclear whether the documented fossils were from chert clasts within the Altamaha Formation or from in situ residuum. Huddlestun and others ( 1974) classified the fossilifierous chert in similar residuum as Late Oligocene. In the present map area, casts and molds in che11 found in residuum may be the pecten Chlamys (Anatipopecten) onatipes and the pelecypod Glycymeris cookei.

STRUCTURAL GEOLOGY
The Andersonville Fault is the principal recognized sti"LICture within the current map area. This fault extends in an east-west to slightly northeasterly direction principally along Sweetwater Creek. Maximum vertical displacement is about I00 feet and down to the no11h (Zapp, 1965). Zapp indicated that this fault passes into a steep north-facing monocline that dies out to the west of the town of Andersonville. Vertical displacement to the east decreases to about 60 feel. Studies by Owen (1963), Vohris ( 1972), and Cofer and Manker ( 1983) suggest the total traceable length of this fault is on the order of 20 miles from Schley County to Dooly County. An unpublished aeromagnetic anomaly map of Georgia (Daniels, date unknown) shows a linear anomaly in the basement that appears to be correlative with the Andersonville Fault. Length of that anomaly is approximately 45 miles.
Maps by Cofer and Manker (1983), Rheinhardt and others (1994), and Zapp (1965) illustrate essentially the same faulltwce through the Andersonville district but extend it in slightly different directions to the east and west.

17

The fault as shown on PJates 1, 2 and 4 is based on that of Zapp (1965). The Anderson vi lie Fault as a single fault plane has not been observed in outcrops or mine workings. Deformation and displacement may occupy a zone up to a half mile wide with the fault being marked by flowage of unconsolidated sediments and flexure and rupture of more indurated beds (Cofer and Manker, 1983). Dip reversals and steepening of dips, e.g. up to 60 in the Clayton Formation, are apparent as the fault is approached. Flowage in the form of sand dikes and domes and plastic clays may result from seismic shaking of saturated sediments (Fig. 44).
The amount of displacement increases with depth and may indicate continued but intermittent movement on the Andersonville Fault from pre-Clayton time to at least the top of the Claiborne Formation and perhaps into the Holocene (Cofer and Manker, 1983). Displacement decreases from 91 feet at the top of the Clayton Formation to 64 at the top of the Tuscahoma Formation to 20 feet at the top of the Claiborne Formation. Differential rates of erosion and deposition on either side of the fault resulted in significantly thicker Nanafalia and Clayton Formations on the down thrown side and pinching out of the Tuscahoma Formation on the up thrown side. Peat deposits, noted earlier, that lie below the present surface and within the Andersonville Fault Zone may have formed as a result of fault damming of a Holocene stream (Cofer and Manker, 1983).
Results of shallow, core drilling during this current project could be indicative of a continuation of the Andersonville Fault on the east side of the Flint River. The results were not conclusive, in the opinion of this author, to be definitive. Differences in the elevations of the lower Altamaha Formation contact encountered in the drilling could also be explained by the unconformity at the base of that unit. Deeper drilling is necessary to define other contacts unaffected by unconformities.
Linear and abrupt changes in the directions of the major streams in this map area may be related to additional, unmapped structures. Two of the major stream orientations (N60W and N55E) coincide with principal joint directions in the mines (Cofer and Manker, 1983).
Discrepancies in elevations of mapped contacts in other parts of the current map area may indicate the presence of additional faulting. Faults were not placed on the geologic maps, because the approximate location, orientation, and existence of those potential faults could not be defined without more data.
Differential dissolution of the carbonates of the Clayton Formation and collapse of the overlying sediments were suggested to be the cause of shallow surface depressions in the current map area (Zapp, 1965). As nearly all of these depressions are located within the Altamaha Formation, it would be unlikely that dissolution and collapse would only atfcct the uppermost rock unit and not the intervening units. Also, in all the mine exposures, no collapse and resulting contact displacements in the Nanafalia and Tuscahoma Formations, Claiborne Group and Altamaha Formation were observed (Figs. 6, 7, 11, 18, 19, 20, 21, 22, 26, 27, 29). Dissolution of Eocene- Oligocene carbonates bei1eath the Altamaha Formation has been suggested as a possible cause. This may be possible; however, in all areas mapped by Cocker (200 1, 2002 and this report) these carbonates have either been completely weathered or altered to chert and clay prior to Altamaha sedimentation. A more inclusive origin of these depressions has not been determined. If dissolution ofunderlying carbonates did occur, these were not observed in any mine exposures.
ECONOMIC GEOLOGY
History of the Andersonville Bauxite District
Bauxite was discovered in the Andersonville bauxite district in 1912 at the old Hatton or Old Sweetwater mine that is located at the eastern end of the district (Fig. 45). Mining began in 1914 at the Hatton mine by the Republic Mining and 1'vlanufacturing Company. Other mines opened during World War I included the Easterlin, McMichael (Boggy Bra11ch) and English mines. Production up through World War II was primarily of bauxite. Estimated production at ~hat time was 400,000 tons (Zapp, 1965). The American Cyanamid and Chemical Co. purchased the Hatton mine i;1 1930 and was the only producer in the district for at least 27 years (Grumbles (1957). Other properties operated by the American Cyanamid and Chemical Co. include the Thigpen, Cavender, Lane McMichael (Boggy), Norris-Pierce, Holloway-Easterlin, and Easterlin No. 2 mines (Grumbles, 1957). Currently, the Mullite Corporation of America (Mulcoa) operates a plant and mines bauxite, kaolinitic bauxite and high alumina kaolin ore from several pits in this district. Open-pits that were active during the current mapping include the Easterlin 278, Fowler, Guy-Pierce, Justice-Holloway, and Thigpen mines (Fig. 45).
Bauxite and high alumina kaolin deposits of the Andersonville bauxite district are mined in the Andersonville, Pennington quadrangle in the current map area and the Ideal South quadrangle north of the Andersonville quadrangle (Fig. 45). The presently defined Andersonville district extends approximately 14 miles in a northwesterly direction and is 7 to 8 miles wide. Portions of this district lie in Macon, Schley and Sumter counties.
18

The bauxite and kaolin deposits occur entirely within the Nanafalia Formation. Mining is confined principally to the Nanafalia Formation in the Sweetwater and Camp Creek stream valleys and their tributaries. Primary road access is from Stale Highway 49 that runs from northward from Americus through Andersonville to Oglethorpe and Montezuma (Fig. 45).
Initially, mining concentrated on high-grade ore, i.e. bauxite, at or near the surface in the valleys formed by Sweetwater Creek and Camp Creek. Subsequent mining has removed increasing amounts of overburden or earlier mine waste (Figs. 46, 47) and increasingly relies on kaolin, kaolinitic bauxite and bauxitic kaolin for ore. Fortunately, much of the overburden is composed of soft sand of the Claiborne Group or Nanafalia Formation that can be removed by excavators and front-end loaders. Where present, the more indurated, red argillaceous sandstone of the Altamaha Formation is used to stabilize the haulage roads .
Total bauxite production from Georgia up through 1976 was approximately 1,764,000 tons with the bulk of that coming from the Andersonville District (Patterson and others, 1986). Production of kaolin up to that time is unknown but was probably only a small fraction of the total tonnage. Ore reserves for the district (Table 3) were most recently re-evaluated by Cofer and Manker ( 1983 ).

Table 3. Estimates of Resources in Millions of Dry Tonnes

Reso urce Type Identified indicated reserve Identified JJ!lta.marginal resource Identified submarginal resource In fe rred reserves Hypothetical resources Total Resources

Bauxite 1.23
0.6 1.5 3.3 3

Bauxitic Clay 4.92
2.4 6.0 13.32

Kaolin 290
50
50 390

Sandy Kaolin 240
50 290

As part of the World War II Strategic Minerals Investigation program, the U.S. Geological Survey and the U.S. Bureau of Mines conducted a mapping and drilling progmm in the district to investigate the potential bauxite reserves of the district (Beck, 1949; Zapp, 1948, 1965). More than 1, I00 holes were dri lied , with more than 600 widely spaced (approximately 1,000 feet) wildcat exploration holes and the remainder as closely spaced deposit delineation holes on 200-foot centers. Most of the wildcat holes were located in the overlying Claiborne Group near the mapped, upper contact of the Nanafalia Formation. That evaluation was restricted by the location of the drill holes (Zapp, 1965).
A re-ev<iluation of the kaolin and bauxite resources of the Andersonville District (Cofer and Mankin, 1983) consisted of mineralogical, sedimentological, and paleo-environmental studies of the kaolin and bauxite deposits . In addition, appmximately 600 exploration holes, which were drilled by mining companies from 1960 to 1975, were logged and used to construct a series of computer generated maps of the district. The re-evaluation included a geologic map, a structural contour map of the top of the Clayton Formation, and an isopach map of kaolin containing less than 15 percent sand and silt (Fig. 16). Estimates of kaolin, sandy kaolin, bauxite and bauxitic clay were derived from an analysis of the drill hole data, computer generated maps, and knowledge of the known deposits.

Mining methods

Current mining methods involve the stripping of overbmden, usually Claiborne Group sands and any additional sediments from the Altamaha, Tuscahoma and Nanafalia Formations that may be present above the kaolin and bauxite (Figs. 46, 47). Most of these sediments are soft, unconsolidated sands and are easily removed. Grade and ore thickness "redetermined from closely spaced grid drilling.
Ore grades are based on the ratio of bauxite to kaolin and on their chemical composition. Chemical analyses are
for Al20 3, Si01, Fe20 3, Ti02, and H20+ with alumina and silica generally being the most important in grade classification (Zapp, 1965, Patterson and others, 1986). Locally, iron oxides may replace the bauxite (Fig. 49).

Geology of the ore deposits

Ore deposits in the Andersonville District consist of bauxite and high-alumina kaolin. These deposits are located in the middle to lower part of the Nanafalia Formation. The higher grade, bauxite deposits occur as thin ,

19

tabular bodies within larger masses of kaolin (Fig. 48). Bauxite grades laterally and vertically into bauxitic clay that generally grades into kaolin. Thickness of the bauxite generally ranges from a few inches to 8 feet with a recorded maximum of 25 feet (Zapp, 1965). Bauxitic clay may be I0 to 20 feet thick above and below the bauxite layer. Aerial extent of the bauxite layers is on the order of2.5 to 12 acres. Most of the known bauxite is found immediately south of the A11dersonville fault and in the vicinity of Boggy Branch and Camp Creek. Bauxite is generally absent in the down-clip, i.e. southern, part of the district (Cofer and Manker, 1983).
Kaolin bodies may be up to 50 feet thick and several hundred acres in extent. The kaolin bodies vary in thickness, in part due to post-kaolin, intra-formational erosion (Figs. II , 12, 13, 14), post-Nanafalia Formation erosion (Figs. 22, 26, 27, 28), and perhaps from original depositional basin conditions (Cofer and Manker, 1983). Although the orientation, as well as, the lateral and vertical shape of the kaolin bodies is not documented, the kaolin isopach map mf\y suggest a northwesterly trending basin with perhaps a number of sub-basins.
Because thicker bauxite deposits are generally associated with thicker kaolin deposits, an isopach map (Fig. 16) of kaolin thickness was prepared to evaluate possible locat ions for bauxite mineralization (Cofer and Manker, 1983). With many of the present and former mines located on the thicker kaolin bodies (Fig. 16), this kaolin isopach map would appear to be a reasonably good predictive tool. Other parts of the thicker kaolin bodies and presently undeveloped kaolin bodies may be under thicker overburden or other restrictions that presently prohibit their development.
Mineralogy of the ore deposits
Bauxite iil the Andersonville district consists generally of dense pisolites or nodules in a porous , oolitic or claylike matrix. The bauxite ore is a mixture of gibbsite and kaolinite with kaolinite being more abundant than gibbsite. Non-oxidized bauxite is generally very light gray. Oxidi zed bauxite may range from cream to brown or red in color (Figs. 46- 48) due to iron oxide staining. In the bauxite ores, gibbsite occurs as crystalline aggregates with kaolinite in the form of oolites, pi so lites, and crystalline vein fillings.
Kaolin is generally a massive, fine-grained, plastic clay with color patterns similar to that of the bauxite. Kaolinite is the dominant clay mineral with average particle size less than I ).lin. kaolinite (Cofer and Manker, 1983). Kaolinite crystallinity varies from moderately good to poor ( 1.4 to 0.25) and is poorer (0.5) in the lower part of the kaolin knses as compared to the upper part. Crystal linity is best (1.2) and particle size is greatest, with books, laths and 'Lacks of kaolinite, where kaolinite is associated with bauxitic material. Crystallite size is large, i.e. greater than 1 ~Lill, ai1d crystallinity is moderately good at the top of kaolin bodies where the Tuscahoma Formation has been removed and the Claiborne Group sands lie on top of the kaolin. Crystallinity and grain size ofthe kaolin appea1s to be greate1 in th e upper parts of the kaolin bodies that have been exposed to sub-aerial weathering where the bauxite was formed or where the Tuscahoma Formation was removed by erosion prior to Claiborne deposition. In the southern part of the district, where the kaolin has not been at or near the surface, illite and illite-montmorillonite are more abundant, and kaolinite crystallinity is low and grain size is small.
Other major minerals in the Nanafalia Formation may include quartz, muscovite, illite, and montmorillonite. Quartz is the dominant mineral in the sandy and silty portions of the formation . Muscovite and illite occur as fine sand, silt and clay-size particles and are more abundant in the kaolin bodies. Muscovite occurs as relatively clear, unaltered compact books, altered expanded books and stacks, ragged flakes and parti ally kaolinized fragments that range in size from I mm to 0.2 mm (Cofer and Manker, 1983). Smaller particles consist generally of expanded feathery edged , cloudy to nearly opaque grains. Mu scov ite is more abundant in all kaolins that have no bauxitic material, is less abundant in bauxitic kaolin and coarsely crystalline kaolin , and generally absent where gibbsite is the principal component. Illite content increases with depth and is most abundant in the lower 3 to 5 feet of the kaolin and is rare where montmorillonite is abundant. Montmorillonite is most abundant in the kaolin bodies in the southern and southwestern parts of the district. Where present, montmorillonite is most abundant in the upper 3 feet of the kaolin. This clay is also more abundant in the upper 3 feet of the kaolin where marine strata overlie the kaolin or sandy kaolin, and montmorillonite may fill dessication cracks in the upper part ofthe kaolin.
Additional minerals include hematite, goethite, pyrite, marcasite, siderite, ilmenite, rutile, brookite, tourmaline, staurolite, kyanite, sillimanite, diopsi de, xenotime, monazite, and zircon (Cofer and Manker, 1983; Flock, 1966). G lauconitc: and berthierine are locally present and are more common to the southwest. Pyrite and marcasite are relatively abundant below the water table and in organic-rich sediments. Pyrite may be found throughout the kaolin bul is mo1e abundant in the upper pOLtions of the kaolin where it is overlain by pyritic and lignitic clays and silts. Siderite is the most abundant iron mineral where pyrite is absent and is generally absent where pyrite is present. Hematite f\nd goethite are ubiquitous in all weathered portions of sediments in the district. Heavy minerals are present on the order of 0.5 % in sand units and less in clays and silts. Heavy minerals are generally more abundant
20

and angular in kaolin than in bauxitic sediments.
Origin of the ore deposits
Numerous investigations on the Cretaceous and Te1tiary age kaolin deposits in Georgia have proposed a number of different origins for those kaolin deposits. Cofer and Manker (1983) and Kogel and others (2000) summarize and briefly discuss most of the previous investigations and suggest more recent hypothesis concerning the origin and environment of kaolin deposition and subsequent alteration. This discussion draws on the most recent mineralogical and geochemical data provided in Cofer and Manker (I 983) and Kogel and others (2000). In addition, this discussion incorporates some of the ideas expressed by Cofer and Manker (1983) on the Andersonville district in light of studies on numerous bauxite deposits worldwide (Valeton, 1972), the more recent work on the kaolin deposits in central and eastern Georgia presented by Kogel and others (2000), and in regards to the geology documented in this investigation.
Most of the more recent investigations of the Georgia Coastal Plain deposits suggest that the source of and kaolinitic material was a thick saprolitic mantle derived from deep weathering of crystalline granitic rocks of the Piedmont and Blue Ridge terranes. Weathering of feldspars and K, Na- micas to hydrous aluminum silicate kaolin group minerals, i.e. halloysite, illite, kaolinite, by the removal of Ca, Na and K. Ferro-silicate minerals, e.g. biotite, were altered to high iron smectites. Saprolite was eroded and clays and other saprolitic minerals were transported by high-energy streams and deposited in a low-energy environment. Suggested low-energy depositional sites include deltaic e1wironments (Kogel and others, 2000) or estuarine environments (Cofer and Manker, I983). Oxidizing and neutral pH conditions are suggested to be prevalent (Kogel and others, 2000).
Clay minerals were deposited by flocculation in ponds and lagoons on the delta perhaps facilitated by periodic incursions of semi-saline water during storm conditions (Kogel and others, 2000) or by flocculation in the estuarine environment. In the estuarine environment clays were deposited in relatively flat areas, and sand in steeper channels. Kaolins \-\ere cieposited in less saline waters, whereas illite and montmorillonite were transported further seaward before increasing salinity facilitated flocculation. In addition to the clays and sand, abundant dead plant material, e.g. leaves, woody fragments, pollen, was incorporated into the sediments and locally concentrated as lens-shaped organic mud/clay deposits (Figs. 6, 7, 8, 11) perhaps in fresh water swamps landward and brackish or salt-water marshes s~::award. Removal of oxygen by decaying plant material facilitated reducing conditions for crystallization of pyrite in Lh~ mud deposits, patticularly in and adjacent to the lens-shaped organic mud/c lay deposits. Neutral pH conditions are suggested for this type of environment (Kogel and others, 2000).
Emergence of the kaolin bearing sediments related to a marine regression exposed the kaolin to sub-aerial weathering and erosion. Circulating ground water facilitated recrystallization of poorly crystalline kaolinite-illite muds as kaolinite, further leaching ofNa, Ca and K from most of the remaining feldspars, and initial alteration of muscovite to kaolinite. Portions of kaolin bodies elevated above the water table were more subject to lateritic weathering with more extensive kaolinite crystallization and development of bauxite. Bauxitization is facilitated by increased silica removal and intensity of drainage. Illitic, poorly crystalline kaolinitic mud in the lower parts of the Nanafalia F01mation was least affected by this weathering possibly because of less extensive ground water circulation . Oxidizing and acidic conditions initiated oxidation of pyrite, marcasite, and siderite to hematite and goethite along with development of anatase from Ti-bearing biotite (Kogel and others, 2000).
The observed mineralogic zoning in the kaolin - bauxite deposits may be related to circulation of ground water and buffering of the outer and upper pottions of the clay bodies by higher silica activity in the surrounding and overlying quartz sand. The principal reactions involved in weathering of K-feldspar and K-mica (illite) to form kaolinite and in weathering of kaolinite to form bauxite (Garrels and Christ, 1965) require introduction of water and removal of K ions and dissolved silica (H4Si04). Where unaffected by subsequent erosion, the kaolin bodies grade laterally and vertically into kaolinitic sands and eventually to quartz sand. The presence of silica, generally in the form of quartz, tends to buffer the activity of dissolved sili-ca (H4Si04) in ground water and inhibit the formation of bauxite from kaolinite. Kaolinite in the lower and outer portions of the kaolinite bodies was buffered by the presence of quartz sand. Kaolinite, particularly within the larger kaolin bodies, was more susceptible to desilication and formntion of bauxite. Subaerial exposure of kaolin bodies resulting from erosion, pmticularly those immediately south of the Andersonville fault, essentially removed much or all of the overlying quartz sand. As the upper portions of these kaolin bodies were then not subject to buffering by quartz sand, bauxite mineralization was more extensivl!. As drainage was greater on topographica.Jiy elevated portions of the kaolin bodies, dissolved silica was more rapidly removed further facilitating bauxite mineralization. Similar subaerial conditions were realized in those areas in the northern part of the district where the Tuscahoma Formation was removed and prior to Claiborne sedimenta'tion. Resilicification and kaolinization of earlier formed bauxite may be expected to occur in sediments
21

where additional quartz sand was deposited on top of those sediments and silica actiVIty increased in those circulating ground waters. The increased abundance of illite and lower crystallinity of kaolinite in the lower parts of the kaolin bodies may be attributed to these minerals representing more of the original clay-size particle composition of the sediments, and that the lower parts of the clay bodies were least affected by circulating ground water. Kaolinite crystallinity increased toward the top of the kaolin bodies and was greatest in association with bauxite perhaps due to increased kaolinization of K-feldspar, illite, and muscovite, recrystallization of kaolinite, and perhaps due to resilicification of bauxitic material.
Subsequent to initial kaolinization and bauxitization, fluvial and near-shore sands as well as organic-rich, probably rresh water swamp muds were deposited on top of the kaolinitic sediments and locally cut the kaolin deposits (Figs. 7, 8, I l, 12, 13, 14). Kaolin clast-bearing conglomeratic sands are also developed on this intraformational unconformity. Where intertidal conditions existed, bioturbation by shrimp, worms, etc. consumed organic m<ltter.. Cofer and Manker (1983) suggest rising sea level led to the reaction of silica in brackish water with gibbsite to form kaolinite, but this reaction may be due to buffering of silica activity in ground water by younger quartz sand deposited on top of the bauxite. Kaolinite altered to bertherine where sufficient iron was present. Further deposition of kaolin plus montmorillonite and lesser amounts of illite may have occurred at this time (Cofer and Manker, 1983).
Cofer and Manker (1983) suggest that further uplift on the south side of the Andersonville fault along with another regression again exposed the kaolin on the south side to bauxitization. Evidence from the current study could not confirm whether this event in the evolution of the bauxite mineralization occurred.
Early [o..:c:ne marine transgression led to deposition of smectites of the Tuscahoma Formation on top of the Nanafalia clays and sands. Cofer and Manker (1983) suggest gibbsite and kaolinite in the upper portions of the kaolin bodies reacted with sea water to form montmorillonite or with brackish water to form kaolinite. Although Cofer and Manker (1983) indicate that the Tuscahoma Formation was not deposited on the upthrown, south side of the Andersonville fault, this current study documents the presence of the Tuscahoma Formation in every mine exposure south of the fault (Figs. I 1, 17, 18, 19, 21 ). Smectitic clays of the Tuscahoma Formation sealed off the Nanafalia sands and clays to ground water recharge, and promoted reducing and acidic conditions along with bacterial consumption of organic matter.
Subsequent regression during the Middle Eocene exposed the up-dip portions of the Tuscahoma Formation to lateritic weathering and erosion. Oxidation of pyritic Tuscahoma silts and clays is developed in the upper few feet in the southern part of the district and progressively increases in extent to where most of what remains of the Tuscahoma ['ormation was completely oxidized in the northern parts of the district. Thinning and breaching of the Tuscahoma aquiclude by erosion on both a regional and local basis prior to Claiborne sedimentation subjected the kaolin and bauxite to further weathering. Regional erosion of the upper p01tions of the Nanafalia Formation in the northern parts of the Andersonville district exposed portions of the kaolin- bauxite deposits to subaerial weathering and erosion. Oxidizing and acidic pH conditions facilitated further recrystallization ofthe kaolinite and oxidation of organic matter, pyritic and sideritic material (Kogel and others, 2000).
Another marine transgression lasted from perhaps the Middle Eocene into the Late Oligocene covering the area with carbonates and clays. Subsequent regression exposed those sediments to extensive subaerial weathering and erosion prior Lo Miocene Altamaha sedimentation. Subsequent erosion and weathering into the Nanfalia Formation continues up the present. During each episode the sands and clays were exposed to oxygenated, slightly acidic ground water with further kaolinite crystallization and bauxitization, as well as removal of organic matter by oxidation and,bacterial action (Kogel and others, 2000).
HYDROGEOLOGY
Aquifers present in the current map area include the Floridan, Claiborne, Clayton, and Cretaceous aquifers. Depths and thicknesses of these aquifers in the study 01rea are summarized in Table 4. Data were obtained principally from the cross-sections depicted in Plate 4.
Floridan Aquifer
Limestones of the Ocala Group which contain the regionally important Upper Floridan aquifer were found only near the top of drill hole GGS # 137 (Herrick, 1961) located near the eastern edge of the Methvins quadrangle (Plate 3). Limestone was logged from 20 to 46 feet. The extent of that unit in the subsurface is unknown, and no outcrops of limesto11e vvcre found in the present map area.
22

Claiborne Aquifer
The Claibome aquifer is composed of Claiborne Group sediments. Claiborne Group sediments increase in thickness to thL: south and southeast and have been partially eroded where they are exposed in the current map area. Erosion prior to Altamaha deposition has also reduced the thickness of the Claiborne Group as illustrated in Plate 4. Depth and thickness of the Claiborne aquifer shown in Table 3 are derived from map data (Plates l - 3) and well data plotted in Plate 4. Recharge occurs principally through exposures of the Claiborne Group sediments or through Quaternary or possibly late Tertiary alluvium.
The Claiborne Group sediments are relatively porous and permeable with soils rapidly drained of moisture during drought conditions. Stock or irrigation ponds dug into the upper portions of the Claiborne Group do not hold water, whereas those dug near the base of the Claiborne Group are more likely to retain water.
This aquifer is locally confined by overlying clay-rich zones in the Altamaha Formation or clay-rich residuum in the Teniary Sediments and Residuum map unit. Throughout much of the study area, downward movement of surface and groundwater is inhibited by the relatively impermeable shale and clay of the underlying Tuscahoma Formation. In the northern part of the Andersonville and Pennington quadrangles, the Tuscahoma Formation is discontimllJU5 or missing. In that area, the Claiborne Group rests on top of the Nanafalia Formation. Ground water commun icatio11 may exist between the Claiborne aquifer and the upper sandstone/sands of the Nanafalia Formation, where present. The extensive kaolin or other clay in the Nanafalia Formation would serve as a confining lithology for the lower part of the Claiborne aquifer. Seeps were found in the Claiborne Group just above the Tuscahoma contact ancl]r, the Nanafalia Formation at the contact between overlying sandstone/sands and underlying clays.
Principal users of the Claiborne aquifer in the current map area are wells for agricultural irrigation (McFadden and Perriello, 1983 ). The Claiborne aquifer provides much of the base flow to at least the smaller streams in the Andersonville, Methvins and Pennington quadrangles. Base flow of the streams could be adversely affected by withdrawals and prolonged drought conditions (McFadden and Perriello, 1983). Water quality, transmissivity and potentiometric surface data for the Claiborne aquifer through 1982 are available in McFadden and Perriello (1983). Water quality, potentiometric surface and water use data through 1986 are provided by Long ( 1989. Estimated irrigation ground-water withdrawals for Sumter County were 9.92 million gallons per day (Long, 1989).
Permcabdity measurements of surface exposures of the Claiborne sediments are reported by Beck ( 1982). Permeability decreased in the more argillaceous portions of the Claiborne sediments and in outcrops that were armored by secondary clays.
Clayton Aquifer
The Clayton aquifer is composed principally of permeable limestones within the middle limestone unit of the Clayton Fonmtion. Depth and thickness of the Clayton aquifer shown in Table 4 are derived from well data plotted in Plate 4. R.:charge for the Clayton aquifer in the current map area is principally in some of the deeper creek valleys within the Andersonville and Pennington quadrangles. Because of weathering of the limestone to a relatively impenneable, clay-chert residuum, recharge of the Clayton aquifer may be through sandier portions of the Clayton and overlying Nanafalia Formations. Relatively impermeable silt and clay in the upper part ofthe Clayton Formation and overlying Nanafalia Formation and in the lower pa1t of the Clayton Formation and upper part of the underlyi11g Providence Sand are the principal confining lithologies of the Clayton aquifer (McFadden and Perriello, 1983).
The Clayton aquifer has not been an important aquifer in the current map area according to data supplied by Long ( 19~9). Deep wells in the Andersonville, Methvins and Pennington quadrangles have penetrated thick sections of Clayto11 carbonate, which may be a potential water source.
Cretaceous Aquifers
In the map area, aquifers below the Clayton aquifer include the Eutaw, Blufftown, Cusseta, and Providence aquifers. Aquifers below the Providence aquifer, i.e. Eutaw, Blufftown and Cusseta, were not considered to be important .gro[ind-water sources in the current map area based on earlier data for well construction costs and problems of water quality (McFadden and Perriello, 1983). Subsurface data for the Providence Formation, which forms the Providence aquifer, is inadequate to provide a reasonable picture of this aquifer in the current map area. Cross-section A-A' -A" in Plate 4 shows essentially the top of the Providence Formation, and the Providence
23

Formation was below the depth of drill holes in the other section. Some ground water communication may exist between the Providence and Clayton aquifers (McFadden and Perriello, 1983). Recharge for the Providence aquifer in the current map area is principally to the north and west in Schley and Macon Counties.

TABLE 4.

Aquifer characteristics in the study area.

Aquifer Floridan Claiborne Clayton Providence

Rock Units
Ocala Group limestone
Claiborne Group (including Lisbon Formation where present) Clayton Formation
Providence Formation

Depth 20 to 46 feet 0 to 30 feet 0 to 300 feet 40 to +450 feet

Thickness 26 feet 40 to 160 feet 30 to +185 feet unknown

GEOLOGIC HAZARDS
Several l'rnportant geologic hazards that were observed during the STATEMAP program involve soft, commonly unconsolidated sands and locally soft clays. Most of the soft sands belong to the Claiborne Group and to the upper part of the Nanafalia Formation where present. The soft clays belong principally to the Tertiary Sediments and Residuum unit, although some may be found in the Altamaha, Tuscahoma, Nanafalia and Clayton Formations. Local masses of chert blocks belonging to the Tertiary Sediments and Residuum unit may constitute a hinderance or an obstacle in road construction and perhaps may be considered as a geologic hazard.
Principal hazards of the soft sands include rapid erosion of farmland, roadways, and undercutting and collapse of stream and road banks. Most of the farmlands observed during the five years of mapping in the STATEMAP program are developed on soils on the Altamaha Formation. Clays and cemented portions of the Altamaha Formation prevent rapid erosion of those soils. Rapid erosion of sandier soils on hillsides underlain by the Claiborne Group may in.itiate gullying that may encroach into the overlying Altamaha Formation and the soils developed on top of thot unit. Generally, as the slope becomes steeper, erosion and gullying becomes more rapid. Many of the hillsides odjacent to stream valleys have been left to grow as forested land to help prevent erosion. Roadways that run down to creek and river valleys and drainage ditches adjacent to the roadways serve to channel runoff and are particularly susceptible to erosion where they are underlain by the Claiborne Group sands . Where the roadways are paved, the drainage ditches are commonly cemented. In other places, miscellaneous material such as recycled concrete blocks, tires, kitchen appliances, etc. have been placed in those ditches to slow the runoff and resulting erosion. Undercutting of road banks of as much as 10 feet has been observed in the Parrott quadrangle (Cocker, 200 I), and with subsequent collapse within a few months of that observation. Similar steep, undercut road banks were obsl:rved in the Andersonville, Bottsford, Lake Collins, Plains, and Shellman quadrangles. Most of the affected nreas are along relatively lightly traveled roadways and have not been a high priority to local government agencies.
Erosion and undercutting of stream banks may be especially hazardous where structures or infrastructures are involved. Erosion and undercutting of stream banks where gas, water and sewer pipelines are exposed may cause these pipelines to collapse and rupture. Buildings that are placed on the edges of stream banks are also subject to erosion and undercutting of the stream banks. Areas that have been built up and paved over are more susceptible to increased runoff, erosion and stream bank undercutting. Hazardous conditions of stream bank erosion that affect buildings and infrastructures were observed mainly in and adjacent to the city of Americus. The presence of the Claiborne Grot1p at or near the surface and numerous, commonly deeply dissected streams, as well as the numerous buildings, roads, parking lots, and concentrated infrastmcture increase the geologically hazardous conditions in Americus. Similar conditions may develop related to the soft, upper sands of the Nanafalia Formation. As this rock unit is exposed mainly in more rural, undeveloped areas and crops out more towards the bottoms of hillsides that are generally not cultivated, geologic hazards related to this unit are less common. In addition, the upper soft sands may be removed b)' local disconformities.
Soft clay of the Tertiary Sediments and Residuum unit are a geologic hazard especially when the clay is wet. The most frequently encountered hazard is found on unpaved roads where the slippery conditions may quickly send

24

a vehicle off course into a ditch, tree or another vehicle. Clay-rich roads that have dried out after a recent rain may have deep. irregular ruts from vehicles that have swerved back-and-forth trying to traverse the slippery mud. These conditions are also hazardous as a vehicle may bounce out of control from one rut to another. Local road graders may need to frequently smooth out the ruts. Less common, clay-rich portions of the Altamaha, Tuscahoma, Nanafalia and Clayton Formations may locally influence road conditions in a similar manner.
SUMMARY
Geologic mapping of the Andersonville, MetllVins and Pennington quadrangles quadrangles (Plates I - 3) show the interpreted distribution of Te11iary and Quaternmy sediments. Cross-sections (Plate 4) show the interpreted subsurface geology based principally on the mapped surface geology. Exposed stratigraphic units in these quadrangles consist of the Lower Paleocene Clayton Formation, Upper Paleocene Nanafalia Formation, Upper Paleocene to Lower Eocene Tuscahoma Formation, Middle Eocene Claiborne Group, residuum of possibly Eocene and Oligocene sediments (Tertiary Sediments and Residuum), and the Miocene Altamaha Formation. Late Tertiary (?)to Quaternary river terrace alluvium may be present on flat, terrace-like areas adjacent to the Flint River but none were identified in either mapping or core drilling on either side of the Flint River. Sediments found in those drill cores werL' si'milar to Tertiary sediments exposed in adjacent areas rather than alluvium. Quaternary alluvium is found in stream valleys.
Episodes of exposure, weathering, and erosion followed the deposition of the: 1) Upper Cretaceous Ripley Fonnatio11, ::!) Upper Cretaceous Providence Formation, 3) Lower Paleocene Clayton Formation, 4) Upper Paleocene Nanafalia Formation, 5) Middle Eocene Claiborne Group, 6) Upper Eocene Ocala Group, 7) Oligocene sediments. and Miocene Altamaha Formation. Intraformational disconformitites were observed in the Nanafalia Formation. The complex depositional, weathering, and erosional history of these Coastal Plain sediments pose a number of mapping and stratigraphic identification difficulties. The Clayton, Nanafalia, and Tuscahoma Formations, the Claiborne Group, the Tertiary Sediments and Residuum, and the Altamaha Formation were observed to vary considerably in thickness, and may be entirely absent in some areas.
Several key stratigraphic outcrops and observations that were identified and mapped will be useful for future mapping and perhaps resolution of stratigraphic ambiguities. Numerous exposed contacts between the Altamaha Formation, the Tertiary Sediments and Residuum unit, and the Claiborne Group illustrate local erosional relief. The basal conglomerate of the Altamaha Formation is recognized as a key marker bed in the stratigraphic section in this part of tilt' Coastal Plain (Cocker, 200 I) and was again useful for identifying the lower contact of the AItam aha Formation. Multiple episodes of alteration have obliterated primary sedimentary textures in many Coastal Plain sediments.
Recharge of the Claiborne aquifer occurs through the Claiborne Group sediments in the Andersonville, Methvins and Pennington quadrangles. Permeability of the Claiborne Group sediments is adversely influenced by an increase in clay content. Recharge of the Clayton aquifer may occur where it is exposed in the Andersonville and Pennington quadrangles although the Clayton Formation is represented mainly by a clay and shale residuum in these areas. Recharge of the Providence Formation occurs probably in the quadrangles immediately north of the Anderson vi lie and Pennington quadrangles. The mapped distribution of the chert and clay residuum found between the Altamaha Formation and the Claiborne Group marks the theoretical limit of the Upper Floridan aquifer. Recharge of the Upper Floridan aquifer in the map area is probably minimal because of the impermeable clays and chert in the residuum as well as the thin and discontinuous nature of the Tertiary Sediments and Residuum unit.
The bauxite and high alumina kaolin deposits of the Andetsonville District are an important economic resource in the current map area and in this part of Georgia. These deposits are located in the middle to lower part of the Nanafalia Formation. The deposits vary in thickness, in part due to post-kaolin, intra-formational erosion, post Nanafalia Formation erosion, and perhaps from original depositional basin conditions. Variations in grade are related to thl' original depositional conditions, i.e. quartz sand to kaolin ratio, and post depCJsitional weathering that initially altered the kaolin partially to bauxite and then bauxite to kaolin.
Geologic hazards identified during the course of this and previous year's mapping are related mainly to the soft sands of the Claiborne Group and the clays of the Tertiary Sediments and Residuum. Rapid erosion of unprotected, soft, Claib.orne Group sands can cause destruction of farmlands and roads, and imperil buildings and infrastructures such as pipelines due to stream and road bank failure and collapse. Both wet and hardened , rutted clays of the Tertiary Sediments and Residuum in the beds of unpaved roads may cause loss of vehicular control and result in crashes.
25

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26

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Rountree, R. G., Arden, D. D., Jr., and Jones, F. B., 1978, Evidence for faulting in Sumter County, Georgia: Georgia Jourmd uf Science, v., 36 , #2, p. 94.
Summerour, J. H., 1999, Geologic atlas of the Byromville, Drayton, and Leslie, Ga. 7.5 minute quadrangles: Georgia Geologic Survey Open File Report 99-1,42 pp., 4 pl.
Summerour, J. H., 2000, Geologic atlas of the Smithville East, Smithville West, Ga. 7.5 minute quadrangles : Georgia Geologic Survey Open File Report 00-1, 63 pp., 5 pl.
Toulmin, L. D. and LaMoreaux, P. E., 1963, Stratigraphy along the Chattahoochee River, connecting link between Atlantic and Gulf Coastal Plains: American Association of Petroleum Geologists Bulletin, volume 47, #3, p. 385-404.
Valeton, 1':, 1972, Developments 111 Soil ScieHce 1 - Bauxites: Elsevier Publishing Company, Amsterdam, The Netherlands, 226 pp.
29

Vorhis, R. C , 1972, Geohydrology of Sumter, Dt>'Gl'ly, Pu~aski, Lee, Crisp, and Wilcox counties, Georgia: United Slate:~ 1 gi.ca l Survey Hydrologic Invest~ti<l1ns Atlas HA 435, 1:250,000 scale, 2 pl.
Zapp, A. . .. I 48, Geology of the Andersonville blilJ~Jix.ite district, Georgia: United States Geological Survey Open File Report 28, 60 pp., 7 pl.
Zapp, A. . I 65, Bauxite deposits of the AnGi~rSGlnvme District Georgia: United States Geological Survey Bulletin 1199-G,.p. d-G37 ., 3 pl.
Zapp, A. D. u.n u Clark, L. D., 1965, Bauxite tlll ~~has adjacent to and between the Springvale and Andersonville
Di stricts G~o rg ia : United States Geological Slilll'v~y Bullretin 1199-H, p. H1- Hl 0,1 pl.
30

APPENDIX

t'ill Hole Logs for the STATEMA..P Program (March, 2003 through July, 2003)

Drill Hoi : Drilled: Locai' io n : Total tl ep !h: Eleva li on:

GGS #4017 (by-1) March, 2003 Byromville Quadrangle 46 feet 314 feet (near bench mark)

Depth 0- 0.5'

Description massive, brown to dark brown, nGYliH~~mented, fine-grained sandstone

0.5 -2.5 '

massive, medium rusty brown, filtleJru.ineGI sandstone

2.5 -4.0 ' 4.0- 11. 0'
11.0.,... 19 . ~

massive, weakly argillaceous, Q'J'llim'JC, fine-grained sandstone
moderately argillaceous, oralfiii~C wi1lln light gray patches, fine-grained sandstone; minor quartz pebbles; local light gray patc~s ofc1ay, especially at 5' and 10'
pale orange/yellow, weakly mfCaJ<>"GlWs, fine-grained sandstone

19.0

2" thick, light brown - greenisn lurowlll clay layer

19.0- 24 .:5 '

light tan to orange, fine to coa.tseira,ined, sandstone; locally kaolinitic; subangular to subrounded, small quartz pebbles (</= 0.5'')

24.5-31 .:'

massive, light tan to light gray Ggnt'GI,ilJ!g d'Ownward), medium to coarse-grained sandstone; locally coarser-grained with subrounrrd.~Gl Cii'1Jl!lil'tz p-ebbles(</= 0.75") especially at base; locally kaolinitic; common fine-grained black ot' cdiatk green grains

3 1 . 5 - 4 6 .0

white, non-cemented, fine-grained sand/sandstone, minor fine-grained, black grains; flowing sand at base; water table

ror mati ous 0- 46.0'

Claiborne Group (Tallahatta Flilftnialtion)

21

Drill Ho le: Drilled: Locatiou : Total depth: Ele ation:
Depth 0 - 2.5 t
2.5 - 12. _, 12.5- 17..-
17.5-2 1.-
21.5-2 .u
26.0 '- 35..:\

GGS #40 18 (by-2) March, 2003 Byromville Quadrangle 50 feet 365 feet (approximate)
Description
no recovery
massive, brick-red, argillaceous, fin'CwJrained sandstone; iron-stone pebbles (abundance unknown) massive, brick-red to weakly mx~ttlcd, argillaceous, fine-grained sandstone; rounded qumtzite pebble at 13.0'
massive, brick-red, very fineJt"alitt~<il sandstone; little or no clay
massive, strongly mottled, w~aldy ariillaceous, very fine-grained sandstone; increasingly argillaceous below 25'
massive, mottled, brick-red to reddish brown, very fine-grained sandy clay and clay; contact at 35.5'
massive, fine-grained, nonwcevn-em'tcG!, sandstone/sand, white to light gray to mottled light brown in lower 5', rusty stained in uppcn 1'

Formati 11 0-35 .5' 35.5- 40'

Altamaha Formation (perhaps t~rtiary sediments and residuum in lower 10') Claiborne Group (Tallahatta F~t'lination)

32

Drill Hol e: Drilled: Location : Total dcpt tl: E levation : Depth 0-7.5' 7.5- 12.5'
15-19. - 19.5- 37' 37- 38' 38- 50'
Forma ti oJI 0-19.5' 19.5- 50 '

GGS #4019 (by-3) April, 2003 Byromville Quadrangle 50 feet 3 15 feet (approximate) Description massive, brick-red, argillaceolll:S, fme-i!'ained sandstone massive, brick-red, argillaceGJil.IIS, ftne$rairred sandstone, minor mottling massive, brick-red, argillacewl; :tltrc~ifai~d sandstone, moderately mottled massive, brick-red, weakly arpH11ioe'ooo, fine-grained sandstone massive, tan to orange to sugary white, very fine-grained to fme-grained sand/sandstone massive, brick-red, argillaceow to 11\lo'derately argillaceous, fine-grained sandstone massive, tan to orange to SUjlit')' white, very fine-grained to fine-grained sand/sandstone; upper 6" is brick-red
Altamaha Formation Claiborne Group

33

Drill Hoi : Drilled: Location : Total dep th: Elevation :

GGS #4020 (by-4) April, 2003 Byromville Quadrangle 17.5 feet 280 feet (approximate)

Depth 0- 12'
12- 17' 17-17.5' Formation ' 0- 12' 12- 17' 17-17.5'

Description massive, brick-red, argillaceo'll!~, ti:neirained sandstone; fragment of fresh biotite gneiss
at 1' is probably road-bed gravel th!),t r:nay have been dragged down hole
massive, weakly mottled, reddish brown to brown, sticky clay massive, light brown, fine-grai~e-GI s-atl'd/sandstone
Altamaha Formation Tertiary sediments and resid1.11~tn Claiborne Group

Drill Hoi : Drilled: Locatiom Total deJl l h: El.eva tio11 : Depth 0 -7'
7- 15' 15- 22.5 '
22.5 - 26 .:i I 26.5- 30 .5 30.5-38 .5
Formaliott 0- 22.5' 22.5- 38 .:

GGS #4021 (by-5) April, 2003 Byromville Quadrangle 38.5 feet 340 feet (approximate)
Description
massive, brick-red, argillace'G1us, fine-grained sandstone, weakly mottled from 5 - 7'; small
fragments of fresh biotite gneis;s at 6- 12' is probably road gravel
massive, strongly mottled, ar~HJ.~(;eous, fine-grained sandstone
massive, very strongly mott~etd, iir(iiJ.taceous, fine-grained sandstone; core generally broken into small pieces </= 1"; some are</"" 4''
massive, orangish brown and ffi1Grotled, sticky clay
massive, generally rusty to dark brown to rnedium gray, fine-grained sandstone
massive, rusty red to mottled/varic>jSJted rusty brown and brown, argillaceous, very fine-grained
sandstone to very fine-graine@ sancdy clay to clay; mainly clay in lower 3'
Altamaha Formation
Tertiary sediments and resid~lililim

34

Drill Hoi : Drilled: Location; Total dcp.t h: Elevation: Depth 0- 2.5' 2.5 - 6'
6- l0'
10- 12.5 '
12.5 - 46 .5
46.5 -50 '
For mDti ons 0-12.5' 12 .5-50 '

GGS #4022 (by-6) April, 2003 Byromville Quadrangle 50 feet 312 feet (near elevation point ~n Gfl.laiGitangle map)
Description
no recovery
massive, brick-red, pebbly, ariiU~ceci111s, fine-grained sandstone; pebbles include ironstone and possibly quartz
similar to above interval; pebb!Jes wete not observed, but may be present; appears more argillaceous than above intervaill; weakly mottled with light brown patches <I" diameter
massive, brick-red, argillaceoIJl:S, fi:ne- to medium-grained sandstone; appears to become less argillaceous toward 12.5'
generally finely layered (best pre:B~rved where core is more cohesive), tan to pale yellow to dark red brown to white and light ~ray, ftn~-gr&ined, locally micaceous sand; dark red-brown section at 22.5 - 24.5'and appears to be som:ewhat coarser (fine- to medium-grained); layering is apparent in alternating color bands; fro1101 37 - 4S' are several narrow zones </= 3" of alternating sand and wispy kaolin laminae
massive, light tan to light rec;\) tlll<oGihmtrt-grained sand, distinctly coarser than above interval; water table at 47.5'
Altamaha Formation
Claiborne Group

35

Drill H oi : Drilled: Location: Total d ept h : Elevation :

GGS #4023 (by-7) April, 2003 Byromville Quadrangle 47 feet 320 feet (approximate)

Depth 0 - 2.5' 2 .5- 5.0 ' 5.0- 12. 5
12.5-25 ' 25- 29.5 '
29.5- 44. -
44.5-47' Formati o11s 0- 12.5' 12 .5 - 47 '

Description no recovery massive, brick-red, argillaceous, fine~ifained sandstone massive, mottled, generally ~riGk-red, white and brownish-red, argillaceous, fine-grained sandstone massive, generally orange to locallly light gray, very fine-grained to fine-grained, sandstone/sand massive, orange to light gray/white, medium- to coarse-grained, sand with minor subrounded to rounded qua1tz pebbles (</= 1") diameter; numerous, small black grains massive, orange to white, v~ry fin'Cgrained to fine-grained, sugary sand with scattered clay laminations/layers approximately 9'0 d-egrees to core axis and 0.25- 0.75 inches thick massive, light green and crimson Gtay with thin sandy laminae that separate the core into segments
Altamaha Formation Claiborne Group

Drill Hol t' : Drilled: Lo atio n: Total dept h: Elevation :

GGS #4024 (by-8) April, 2003 Byromville Quadrangle 50 feet 370 feet (approximate)

Depth 0- 12.5' 12.5- 17.
17.5-47' 47- 50' Formations 0- 12.5' 12.5- 50'

Description massive, brick-red, argillaceous, finegrained sandstone; weakly mottled toward base massive, brick-red (slightly Ug~er tlaan above), moderate to weakly argillaceous, fine-grained
sandstone, less argillaceous wfth 1ncre4lsin:g depth
massive, orange to light rusty ~ay, fim~-grained to very fine-grained sand
similar to above; also contains thin (liS-%") clay layers/laminae at irregular intervals
Altamaha Formation Claiborne Group

36

Drill Hole: Drilled: Location: Total depth: Elevation:
Depth
0~ I'
l - I0'
Formatious
0- 10'

GGS #4025 (by- II) April, 2003 Byromville Quadrangle 10 feet 335 feet (approximate) Description no recovery massive, dark brown , argillaceous to weakly argillaceous, fine-grained sand
Quaternary alluvium (?)

37

Drill Ho le: Drilled: Location: Total deplh: E levation :

GGS #4026 (by-12) April, 2003 Byromville Quadrangle 30 feet 325 feet (approximate)

Depth 0-1' I -6' 6-11.5' 11.5 - 12.5' 12.5- 13' 13- 14'
14- 30'
Formatiotl s 0-11.5' 11.5- 30 '

Description no recovery massive, light green with broWill p~tches, day thinly layered, light green and 'brtJwn to dark brown and black with increasing depth, clay thinly layered, brown and dark btG>'WJ\1, argillaceous sandstone massive, dark brown argillaccli1tliS sa~a<Gkitone approximately 8" of massive, Gl'l'anae, fine-grained sandstone overlying approximately 3" of brown, argillaceous, fine-graiti!lclli s-am.dstone/sandy clay massive, light brown to rusty ~rown, fine-grained to very fine-grained sandstone/sand with patches and streaks of dark \jr<~Mrn tc.l almost black sand; thin clay layers (approximately 1;4'' in lower 2.5'; core is very wet in1ower 2.5'; water table at 27.5'
Tertiary sediments and residulJI\In ulait Claiborne Group

38

Drill Hoi : Drilled: Location : Total dep (h: Elevat ion :

GGS #4027 (dr-1) April, 2003 Drayton Quadrangle 25 feet 3 12 feet (near elevation mark)

Depth 0- 0.5' 0.5-1 .5 1.5- 8' 8'
8 -21 '
21-25'

Description
no recovery
massive, dark brown, fine- to ntr~diliungrained sandstone
massive, brick-red to moderaltieiy nrcildish brown with increasing depth, weakly to moderately argillaceous, fine- to medium- ira.i.ne'<d sandstone
2" thick, massive, light gray, fQ:le tm Goarse-grained sand; weakly micaceous with minor small black grains
massive, moderately reddish Wl'lilWn, geneially medium- to coarse-grained, argillaceous, weakly micaceous sandstone
massive, tan to light gray, tnedium- to coarse-grained, kaolinitic, moderately micaceous sandstone/sand

o nnMioos 0-25'

Claiborne Group ?

39

Drill Hole: Drilled: LocHtion : Total d en t h: E leva lion :

GGS #4028 (dr-2) April, 2003 Drayton Quadrangle 45 feet 321 feet (near elevation mark)

Depth 0 -13'
13-17.5' 17.5-20' 20- 26'
26-36.5
36.5 ~ 5

Description
massive, brick-red, weakly m~ttil~C'c.l, argillaceous, fine-grained sandstone; 1.5" rounded quartzite pebble at 10'
massive, brick-red and buff day ~r:rd fine-grained sandy clay; abundant chert clasts
massive, brick-red, weakly arg:vJ.l.-aGeGl'\1~, fine-grained sandstone
massive, brick-red, becoming incrusingly pale-green with increasing depth; scattered black streaks (MnO?)
finely layered, alternating pale green, brown and brick-red, plastic clay; scattered small black streaks (MnO?)
massive, brick-red (36.5 - 3!K')1 li.ght tan to white, very fine-grained sand; argillaceous in upper 1.5'

Fo rmntions 0- 13 JJ - 36.-' 36.5-;45'

Altamaha Formation Tertiary sediments and residuiJ'lin Claiborne Formation

40

Drill Hole: Drilled: Locatio n: Total dcp h: levatio n:

GGS #4029 (dr-3) April, 2003 Drayton Quadrangle 17.5 feet 285 feet (approximate)

Depth 0-17.5'
Fo rmatio ns 0 -17.5"

Description massive, brick-red to tan and li&l1t reddish brown, fine- to medium-grained, weakly argillaceous sandstone/sand; especially reed it! 1Wpper 7.5 '; core wet below 11' and especially from 15 - 17.5'; scattered rare coarse-grained qulllttz; 1" white chert ? clast at 4.5'
Claiborne Group

Drill Hol e: Drilled: Location : Total d ep t.h: Eleva t-ion :
0 -6'
6-17.5'
17.5-21 '
21-30'

GGS #4030 (dr-4) April, 2003 Drayton Quadrangle 30 feet 325 feet (approximate)
massive, brick-red, argillaceous; tlne&rained sandstone
massive, strongly mottled (briok-tc'd i!Ud white) sandy clay and argillaceous sandstone
abundant, strongly weathered G~!'t it! brown, sticky clay
massive to thinly layered, pale grc~n to various shades of brown, plastic, sticky clay

Formatio n. 0 - 17.5' 17.5- 30'

Altamaha Formation Tertiary sediments and residuu:m

41

Drill Hol e: Drilled: Lo cation : Total depth: Elevatinn :

GGS #4031 (dr-5) April, 2003 Drayton Quadrangle 42 feet 273 feet (near benchmark)

Depth 0-1' I - 1.5' 1.5-23 ,
23-41,
41- 42'

Description
no recovery
massive, dark brown sand
massive, generally light reddish ~rown, mottled buffto reddish brown from 10- 15', argillaceous, fine- to coarse-grained sandStG>rt~; gemerally coarse-grained from 18 - 23 '; angu Jar contact with underlying clay @45 degrees to Gore a\lds
massive to thinly bedded, alt~naitin'i dark chocolate brown to light brown, locally black streaks
and rusty brown, plastic sticky clay; SCilft from 35 - 41 '; especially wet and soft in lower 1'
massive, tan to light brown, medd,lllmgrained, weakly argillaceous sand; very wet

f'orrn a ti oi1 ' 0 - 23 23 - 41 ' 4 1- 42'

Quaternary-Tertiary alluvium ? Tertiary sediments and residuUiltrl Claiborne Group

42

Drill Hole: Drilled: Location : Total depth: Elcvatiou :

GGS #4032 (penn-I) May, 2003 Pennington Quadrangle 25 feet 335 feet (approximate)

Depth 0 -1' 1- 5' 5-12.5 ' 12.5- 17.5'
17.5- 18 18-20
20- 25'
Fo rmati ons : 0 -25'

Description no recovery massive, light reddish brown, finre t<il tnedium-grained sandstone/sand massive, light brick-red, weakly ar~HJ:aceous, fine- to medium-grained sandstone massive, medium reddish b'l"<ilWiil) weak to moderately argillaceous, fine- to coarse-grained sandstone; grain size increase's C'IS'p'eCi41lly in lower 2.5'; speckled with kaolin and mica especially in lower 2 .5' 8" thick massive, light green and recl:rilish clay massive, brick-red, weakly ilirgiHaaoous, medium-grained sandstone with minor small kaolin grains massive, reddish brown to ligltt brtilwm, kaolinitic, medium- to very coarse-grained sandstone; wet in lower 2.5'
Nanafalia Formation(?)

43

Drill Hol t': Drilled: Location : Total dcp h: I~ leva ti nn :

GGS #4033 (penn-2) May, 2003 Pennington Quadrangle 30 feet 335 feet (approximate)

Depth 0-0.5' 0.5- 10' 10- 13.5 '
13.5- 23 -
23.5-2:
25 - 27 ' 27 - 30'
Fo rm at ion ' : 0- 30'

Description no recovery massive, brick-red, argillaceouiS, i'iwleifained sandstone massive, brick-red, weak to tn'(I)'G!retately argillaceous, medium- to coarse-grained sandstone; minor small white specs (kaolin?) massive, light, rust brown to tallil to white, weakly kaolinitic, weakly micaceous, generally fine- to medium-grained sand; generally Goarscr grained toward base massive, light gray, kaolinitirc, Goa.rse- to very coarse-grained sandstone/sand; angular chert pebbles and kaolin clasts massive, brown, coarse-grainecd Hn1~tone; angular chert pebble
massive to thin-bedded, light p-ay, ftne- to medium-grained sandstone; clasts and thin layers of
kaolin; wet in lower 3'
Nanafalia Formation

44

Drill Hol e: Drilletl : Location : Total depth: < levation !

GGS #4034 (penn-3) May, 2003 Pennington Quadrangle 20 feet 285 feet (approximate)

Depth 0- 1, 1 -4.6' 4.6- 5' 5-9'
9-10' 10- 17' 17- 20'
f ormati on. : 0-20'

Description no recovery massive, light reddish brown, w~ly ~rgillaceous, fine-grained sandstone/sand
massive, dark brown, weakly a;rjii1:a<ltrG>us, fine-grained sandstone massive, medium brown to liib't ~G!IC!iisah brown, weakly to moderately argillaceous, gritty, finegrained sandstone; becomes irr~r~e!$iniiY argillaceous in lower 1.5 - 2 feet massive, variegated, light rusty ]jjrowLl~, argillaceous sandstone/ hard sandy clay massive, weakly mottled to sobiGl whit~, kaolinitic sandstone; kaolin increases with depth
massive, rusty brown to light bl"GlWn, argillaceous, fine-grained, weakly micaceous sandstone; wet in lower 2.5 feet

45

Drill 1-f ol : Drill ed : Loc.:1ti on : Total d pth: Elevation :

GGS #4035 (penn-4) May, 2003 Pennington Quadrangle 40 feet 342 feet (approximate)

Depth

Description

0 -1'

no recovery

1- 13,

massive, light red to brick-red (1-5' ~rrd 5-13 ', respectively), fine-grained sandstone/sand

;

13-17.5 '

massive, brick-red, moderately a~~tgma~eeous, fine-grained sandstone

17.5-19'

massive, brick-red, fine to coar~~IJraiitled, argillaceous, gritty sandstone

19 - 2<1'

massive, brown, moderately ar&Hlac~o,us, coarse-grained sandstone

2.4 - 31.5

massive, brown, weakly argiWilccous, wealcly micaceous, medium-grained sandstone with minor small, white kaolin specks

31.5-38 .5 '

massive and thinly layered, white, sugary, very fine-grained sandstone/sand; alternating gray and white layers define layering

38.5'

2-3 inch thick, white to very light iriy kaolin clast or layer

38.5- 40 '

massive, very light gray, medhwm grainred sandstone; minor small black grains

orm ati u11s:

0-40'

Nanafalia Formation

46

Drill Hole: Odllcd: Locatio n; Total dct> h; Elevati o n:

GGS #4036 (penn-5) May, 2003 Pennington Quadrangle 37 feet 365 feet (approximate)

Depth 0- 1, 1- 5.5' 5.5- 7.5' 7.5- 3:'
35-3 7 Forma tions: 0-37'

Description no recovery massive, light reddish brown, flirrc~rained sand massive, brick-red, weakly arpl!~GeGl~IS, fine-grained sandstone/sand massive to thinly layered (crQS.,s..b'edrding ?), alternating brick-red and light gray to tan layering similar to that observed in outcrops of Claiborne Group sandstone massive, light orange brown, medh.ungrained sand; wet
Claiborne Group

Drill H 11 ; Drill ed: Loc.1tion . Total dcpt ll : Elev a tiou :

GGS #4037 (penn-6) May, 2003 Pennington Quadrangle 27.5 feet -340 feet (adjacent to bench maitk)

Depth 0 - 5' 5 -10' 10- 14' 14- 16' 16 - -2.5 ' 22.5- 2" 5' F'o r ma j Ions: 0 - 27.5'

Description massive, light brown, fine-gra,im.ecd sandstone/ sand massive, light brick-red, weakly lllr!giUII!ceous, fine-grained sandstone massive, rusty brown to tan, m~ditrmsrained sand inassive, tan, fine- to medium&ra.ineGl sand massive, tan, fme- to medium-ifai:rre'Gi sand massive, orange to light rusty ~own, fine-grained sandstone/sand; wet
Claiborne Group

47

Drill H I : Orilled : Loca ti o n. Total depth: li:levati n:

GGS #4038 (penn-7) M ~1y, 2003 Penni_ngton Quadrangle 12.5 feet 345 feet (approximate)

Depth 0- 5' 5-8.5" 8.5- 10 .-
Forma tifm,; 0-105 10.5- I_ 5'

Description massive, dark brick-red, argill:aGeous, finegrained sandstone; 2 inches of clay at top; 6 inches of medium-grained sand at 3- 3.5' massive, light brick-red, modetately a,rgillaceous, fine-grained sandstone massive, dark brick-red, motiletately argillaceous, fine-grained sandstone; abundant iron-stone pebbles massive to thinly layered, light rtitldi&h brown to light brown, fine-grained sandstone
Altamaha Formation Claiborne Group

48

UNrTED STATES OEPARTMF;NT OF THE INTERIOR
GEOLOGiCAL SURVEY

STATE OF GEORGIA
DEPARTMENT OF NATURAL RESOURCES EAR!H AN D WATER DIVISION

Georgia Geologic Survey Open-File Report 03-1

AND ERSONVILLE QUADRANGLE
GEOf?C I A 7 5 MINUTE: S ERIES ( T'OPOGRAP HIC)

Plate 1

Locatton Map o- the Andr.rsonv11le 75 mmL tc quudranglc

Tcpoeraphi/ by photoerammetnl: m ethods froll'l aenil l
photoP,raplo!i ta kM 19 72 I' e d ch"Gked 1 97 '
Pr(] er.t!Orl ana lO 008 foot gj d (<,_k<; Gcorf(ra uOor:llrwte
5)'s Pm w ~ o l zt> ne (trt~n~w;rse M~ r<.:etor) J 000 met r ~ U r1 ve~~.al T rans vers e Merea tcrr g n c. t1c~s zooe 1 6 Showrl HI bill!! 1927 N.orth Amenca 1daturn
Fu'\o!l red d ashed I n<'s nd COl~ select~ fence .... nd t w ld hnes where &enc al lv YJs..w le 1>< ll"' <JI pl\o l oNr ap h~ 'T h1 s 111 lvrma+1011 s urlCher::ked

,,,.
~rMr<-<>jl 13e_
""'
"TI\1 I RID /\NV l"72 M~G ~[T ~ MQRTH Do.C ~A-ION ,O.l ( tl<.fil ) F J~ tET

CONTOUR INTERVAL 10 F EET
NAT!UNAL GEOf>ETif: VERI/CAL DATlJM 01' 1929
THIS MAP COMP~._iS WrlH Nl\n QNM. ltfAP ACCIJRACI' STANDARDS FOR SALE BY U S GEO l OG ICAL SURVEY RESTON VIRGIN \,\ 2:_1092 ~ W LOER nESCRIBI NI:: TOPQGI"IAPHIC MAP ~ ANO SYMBOLS lS AVI\ILABU. ON ReQUEST

<0

ROAD CU1SSW!CATION

Pnmafll \'11ghway
h(lrCj St; r f~~e

Ltght dlltt road hard or
1mprmer.:l surfat:e

Sco,;onr.:lary tughYI11Y

haw -;;.urface _ _ _ \.hllmprc,ed todd

Q 0 lntmta e Route [J L1 S Route:

'.:hat~ Ruule

ANDERSONVILLE. GA .
N32 07 5-W8407 5/7 S
1 9 72
AMS '1148 1 N\0 -SER[ES Vll4~

Explanation

Map Units

D

Water

LJ Oal D Ta

Qui:l lellliil} 4lJUVJWil
l!JOCCOC AJlamaha r'ormalmn

C J Tsr Tertiary Sediments and P.es1duum

c:::;{J Tcb Mtddle Eocene Clatborne Group

D
-D

1\u Uppei Paltucene Tus~;l\homa FormaLJuii luf Upper Paleocene Ncmufaha Formubon 'l ei Lower ~aJeocenr. Ciayton Formalmn

Lme of cross-sechon
Well OJ core hole locaLwn Canl.acl (lot<~l~l approxmmlaly)
Faull lrace (lucaled approxunalely) relaltve movement tndtcaled by U(up) and D(down)

Geologic Map of the Andersonville Quadrangle, Georgia
Geology by Mark D Cocker Dtgttlzed and dtgtta1ly compiled by Mark D Cocker Data sources and processmg mformatton descnbed in Georgia Geologtc Survey DocumentatiOn Report 03-01 June, 2003 U S Geological Survey Coo perative Agreement "#02 HQAG0022 ..

UNITED STATES DEPARTMENT Of" THE JNTERIOR
GEOLOGJCA T, SURVEY

--.....
.. --- Qal __,._ . . ; . _/ j \ -.'{)0 - ,_ ~l
.-
/
/
Qal

Georgia Geologic Survey Open-File Report 03-1
Plate 2
Locat wn tlap of Uw Fr,nmn.glon 7~ mmutc quadrangle

Qal

"' -

CJnlol b~ USCS , NO ':i/NOAA, a nd G~o rg1a Gend"tic Su rey T<>r;C!;raphy by plicla~.:n>m 'Tletm: methoos fro~ Mrial ohotog rapJ-1:>:. h ken 1972. F1eld checked 1972
t 'stem, west z.c.ne Hransvese Merc!'lt:.r} 1 JOD-mette Un\tersallr.m~ver s e M en.:~t(Jr ano liCKS, < )M 16, showf\ in tlu~. 192 7 Nart\'1 American d.<~ tum FiC rd 1.\ll~hed lines nd ica te sele<:!l'!d ft>nce ai\CI lo eld lines whe< e ~ :neral'y vo~1bl<1 (l!'l aeria l phCl!ogr.:l p hs rt11~ in!onnat10r1 lii'IChecka:c:!

CITM GRIO MI D L97Z 1>\~~I'IE:ri'C NCIITI1 0\::<;:~lt>~TtON AT CENTER OF SHEET

CONTOUR ~NTERVAL 10 FEET N-11/0NAl GEODETIC VERTICAL D.'oTUM OF 1 929
THIS MAP COMPL!E5 WJT/1 HATIOI'lAl MAP ACCURAC'l STIINllAf!OS FOR SALE 8Y U.S. GEOLOGICAL SURVEY
DENVER, COLORADO 80225, OR RESTON, VIRGINIA 22092 A FOLDEfi DESt.'RISING lOPOORN'HIC liMPS ANO SY'-'!BOLS IS AVAlLAEILE ON REOUES'T

/ -~

I

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'

.. Qal -

tz:2a'AA'o E.

ROAD CU\SSI FICA.TION

Primary higlw~ay,

l'&:-~l du1y road, hard or

hard surface___ ____ - - - - tmprO'Ied surface __- --~

Secondary r, ighwav.

hard surlace . . - - - -- - Un ,mproved road _ ---~- ......-~

C) [J lnl!!n;tate- floute

u S . I~Ollte c~ State Rout~;

PENNJNGTON, GA.
N3207.5-WB400/7 .5
AMS 4148 11 NE-SER;ES VS45

Explanation

Map Units

1::\hc- I Water

D

Qal Quaternary - Recenl Alluvium

D

Qal 2 Quaternary - Recent Alluvmm (older than Qal)

~ Ia

Yliocene All.aruiiha Formahon

D

'l'sr Terlicll'y Sedunenb and Re8itluum

~ !cb
I" /~.f l Tlu

Middle Eocene Claiborne Group Upper Ptdeoume 1'uscahoma Formation

-D

Tul 'l'cl

Upper Paleo~~ne Nanafalia Formation Lower PaleoCne Claylon Fo1umlion

Lme of cross-section
Well or eure hole localion
Contact (located approximately)
Faull trace (located approximal1y) relalive movement mdicalcd by U(u p) and II (down)
l " l Faull trace (projected and located approximately)
lL'_Ij

Geologic Map of the Pennington Quadrangle, Georgia

Geology by Mark D. Cocker Digitized and digitally compiled by Mark D. Cocker Data sources and processing information described in Georgia Geologic Survey Documentation Report 03 -01 June, 2003 U.S. Geological Survey Cooperative Agreement "1102HQAG0022"

UNITED STATES DEPARTMENT OF THE lNTERIOR
GEOLOGJCAL SURVEY

STATE OF OEORGlA
DEPARTMENT OF NATURAL RtSO liRI.ES EARTH AND WATER OLY\SION

Georgia Geologic Survey Open-File Report 03-1

METHVrNS QUADRANGLE GEORGIA
7.5 MINU1 E SERIES (TO POGRAPHIC\

Plate 3

B'

LocatiOn Map of the Methvms 15 mmute qu adrangt.'

'

Mapp; d
Conlo br USGS, NOS/NQAA., and Geerg'1 a Gt odetc S ll rvcy
Topoffr ~ phJ b)' photcg r~m rn"'t n c mBt llod:; fro m ~-amli phai:Qp:~c.p h-;:
t2Ken 1972 Fe'\"l cht:!cked 1972
Pro)ecl on ~nd J D, OOO tool er1d t clc~ G~wrg1,; coo rd n"'te !'.ys tern west .z:one (trans,er~"' MNc.atoq
1000-lf etrl'! Un lver,.al Trans~erse Mo;rr;ator and t1ck'ii,
lOfl~ l ( , shuw11 m biJe 1927 North Atnf'l lr:~r dat um
F1ne red <.h sh~rll1r,es lrH!Icete selected fen(~ ai" d fu:-ld lml;!:; v.i] ere 2C"ncr~ l Y" Sible on a"na l Photographs Tl-s .dorma!mn ,., "'lchec".ed
M.a:p photo1nspected 1981 No maJOI cultvr-e or drafnage r.h.anaes: ohseNed

(Jf fol GRID P.NO 1"72 M~f.llf"TI C N:JHi fl DECl i' JAli()N ~T C::NTER OF $1~<"

T KllOMf:T~E
=~ CONTOUR INTERVA.L 10 FEET NAriOI'JAl G0DET!E VERTICAL DATL!M OF 19 29
THIS MAP COMPUtS WllH NATIONAL M/\P ICCURA..,'( STAH DMlDS FOR SAl.E SY U, S. GEOLOGICAL SURVt:Y
DENVER, COLORADO 80225. OR FIE~'TON VIRGINIA :220S2 A OOLDER DESCFUBING TOI'OGRA.I'"HIC MAPS ANb SYflo!BOLS IS AVAILAili.E 0~ f'I EL1LJEST

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(. > \ GF<JI?GU \ ~ ---.1 QlJA.ORIJ,$1!:: LOC.I.-ION

RO!tD CLASSIFICAT ION

Pnma ry l'nghw a~
hard ::.urf<~::.e

L1ght duty ruad hard or tmproved ~urface _~~~

S<!co r dar~ htgn.ray

haro se~rf<~ce

-~-- Un1mpro...ed rc ~ d _-..,.. ., --- --.

Qln~~da!e Route [~u S Ro1..te Qsta-e RoJte

METHVINS, GA
N3200-W8400/7 5
1972 PHOTO!NSPE CTE D lfiBl
"-MS 4148 H $f;_SERIE~ Vl3~!1

Geologic Map of the M ethvins Quadrangle, Georgia

Explanation

Map Units

c::J Water

Qa t QuaLrnary ll lluvmm

C J Ta M1ocene Allarnaha Fm mallon

D

Tsr Terttary Sedtmenl<i and Restduum

~ 'l'cb

Middle J?.ocene Cla1borne Group (mav mcluJe Ocalu cmJ Lt~llon ~Oi maLwns m southeastern part of quadran~e)

D

Tlu Upper Paleocene Tuscahoma F'ormahon

Lme of cto~-seclwn Well or core hole lccahon Conlact (loailed ttpptox nmltly)

Geology by Mark D. Coc ker Digitized a nd digttalJy comp iled by Mark D. Cocker Data sources and processmg information described ID Georgia Geologic Survey Documentation Report 03-01 June, 2003 US Geological Survey Cooperative Agreement "#02HQAG0022"

NW
A
500
-125 '

A'

Andersonvi ll e Pennington

{1

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r~
~

Georgia Geologic Survey Open-File Report 03-1
Plate 4

~
-~ ~
"

-120

"'

SE
A"
'

200

---

100

-------- ----------------------------?. ------------

----- -

.

1- . ...,.,....---.,.-

]I . . """- . ;/ / - - - ---'1---- - - -- ------- -

Scale

0

2000 feet

--- -- - ---')-... - - -- - --- - --- -o. _ - ---

. ---------

Vertical t<Xaggemti on = 20x Elevation is in feet above Mean Sea Level
Cross-Section A-A' -A" Andersonville and Pennington Quadrangles

200

Kp

100

-

-

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-

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-

-

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------9- ______

---- - - -

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NW
B'
-136

B"
88 ~ ~

SE
BB BB'
-135 400

O(soalevel~

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--.......

j-:--- ; -;._ -- --- --- Ttu - - - - -- ..._ - _,_ - - ... "" "'"' ;., ,;:_ - - -

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Scale

0

2000 feet

Vertical exaggera tion = 20x Elevat ion is in f eet above Mean Sea Level

Cross-Section B-B'-B"-BB-BB' Americus, Methvins Quadrangles

A


SCHLEY CO. ELLAVILLE SOUTH
~ -------------

,-l

M--------~- _....,_ _---- ~

i ., ANDERS0Jo1'VILLE
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1--1 -- - - - - - - - -

MA CON CO .

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PENNIN GTON
- - - ....... ~

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BYRO!>JVILLE
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311

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DOOLY CO.

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700'J
B B'




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LAKECOLUNS
.. nl ~

AMERICUS
~
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~ SMITlfliJLLE WEST
SUMTER CO

SMITHVILLE EAST

M E THVINS
B"
3055
LESL I E

BB lDRA YTON 137

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B

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I -- -------- ---- -------,_----- -- ---- -- -------------- ~ - -- --- ---- --- -
LEE CO

Location Map of Cross-section Lines A-A'-A " and B-B'-B"-BB-BB '-BB". Drill holes are indicated by black dots. N umbers re fer to drill hole

lithologic logs used to construct cross-sections. Many other drill holes within the map area have inadequate or incomplete logs.

I

Quadrangl~ bou~daries shov..'Il as solid lines, and quadrangle names are in italics. County boundaries are shown a..;; d ashed lines, and county
n~m t".~ ~rr.!!! p l.a!.r! D'P~ -

.

1

[=:J
r. -i I
[=:J
f?.)\~iq
@ w~"ij
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I tf ~~J
C:=J 11111111
[=:J

Explanation

Qal Ta Tsr To (?) Tl (?) Tcb Ttu Tnf Tel Kp

Quaternary Alluvium' Miocene Altamaha Formatiod Tertiary Sediments and Residuum' Upper Eocene Ocala Formation(?) Middle Eocene Lisbon Formation (?) Lower to Middle Eocene Claiborne Group - Tallahatta Formation' !Jpper Paleocene Tuscahoma Formation' Upper P aleocen e Nanafalia Formation
Lower Paleocene Clayton Fmmation
Upper Cretaceous Providence Formation

13 5 " ~ ~

Azimuth of section line

L Thic!ruess of Q uate::nary A llu>iUUl b ~n eath ~ :ream s is unlmown .
2 _May iuclude resi<iuum of &ceae to Oli.'!ocene sediments. 3. l~o bt"d arulir;r~gular occurren ce:; of residuum of Eocwe to Oli goce-.oJe sed iments are depicted in cm s.<-secli nru; as erosim>al remnants bas~d orr ub:;ervcd fidd relation>.
Lateral extc.nt of these is Ullkllown. 4. May include the Bushi Marl am.! th~ Usbon formatio!l. 5_Cl~y lithology uot logsOO at ';his interval iu GGS ;'!700 ""d GGS #1.) 7. Clay in~r.-al in ( ;GS #30 55 could be upper pw.t of Nmafa lia f ormation. Inde!crminat~ :fram d:illlOJg:;,

Geology based on surface mapp ing by Mark Cocker Cross-section geology of line A-A' -A" m odified from Zapp (1965) Digitized and digitally compiled by Mark Cocker
J\me, 2003 T his geologic map was funded in part by the USGS National Coop erative Geolugic Map ping Program
U. S. Geologic al Survey Cooperative Agreement # 02HQAG002 2