Geologic atlas of the Brooksville, Cuthbert, Georgetown, and Martins Crossroads, Georgia 7.5 minute quadrangles [2006]

GEOLOGIC ATLAS OF THE BROOKSVILLE, CUTHBERT, GEORGETOWN, AND MARTINS CROSSROADS, GEORGIA 7.5 MINUTE QUADRANGLES
Mark D. Cocker
In cooperation with the United States Geological Survey Cooperative Agreement #05HQAG0016
DEPARTMENT OF NATURAL RESOURCES Noel Holcomb, Commissioner
ENVIRONMENTAL PROTECTION DIVISION Carol Couch, Director
WATERSHED PROTECTION BRANCH Linda MacGregor, Branch Chief
GEORGIA GEOLOGIC SURVEY Open File Report 06-1
Atlanta 2006

GEOLOGIC ATLAS OF THE BROOKSVILLE, CUTHBERT, GEORGETOWN, AND MARTINS CROSSROADS, GEORGIA 7.5 MINUTE QUADRANGLES
(United States Geological Survey Cooperative Agreement #05HQAG0016)
ABSTRACT
As part of the United States Geological Survey's STATEMAP Project, the Georgia Geologic Survey prepared four 7.5 minute quadrangle geologic maps during 2005 and 2006. The current report contains descriptions of the stratigraphic units which have been identified and mapped in the Brooksville, Cuthbert, Georgetown, and Martins Crossroads quadrangles, information on aquifer recharge zones, geologic hazards, and bauxite-kaolin deposits.
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CONTENTS INTRODUCTION........................................................................................................................................................... I
Scope of the mapping project ............................................................................................................................ ...... 1 Methods.................................................................................................................................................................. .. I Previous investigations .. .......................................................................................................................................... 5 PHYSIOGRAPHY AND LAND USE ........................................... .............................................. ....... .... ........................ 6 SOILS ............................................................................................................................................................................. . 7 GENERAL GEOLOGY .................................................................................................................................................. 8 Geologic cross-sections ..... .... ........................... ........ .. ............ .............. .... .......................................... ........ .............. 9 STRATIGRAPHY OF THE BROOKSVILLE, CUTHBERT, GEORGETOWN, AND MARTINS CROSSROADS QUADRANGLES ................................................................................................................................ 11 Upper Cretaceous .......................................... ............... ......... ............ ..................................... ......................... ......... 11
Selma Group ..................... ............ ............. ................. ... .... ... .... .. ... ................................................... ............ .... 11 Cusseta Formation (Kc) ............................................................................................................................. 11 Ripley Formation (Kr) ......................... .............. ................ .. .............. ............................... ....... ....... ...... ..... 12 Providence Formation (Kp) ...................... .................................................. ......................... ... ................... 12
Lower Paleocene ............ ........ ......... ... ....................... .......................... ........................ ................... ......................... 14 Midway Group .......................... ................. ................................................................................ ......... .............. 14 Clayton Formation (Tel) ............................................................................................... ... ........... ....... .. .. .... 14 Porters Creek Formation (Tpc) .................................................................................................................. 17
Upper Paleocene to Lower Eocene .......................................................................................................................... 17 Wilcox Group ................................................................................................................................................... 17 Nanafalia Formation (Tnf) ......................................................................................................................... 17 Tuscahoma Formation (Ttu) ...................................................................................................................... 20 Hachetigbee Formation- Bashi Marl Member........................................................................................... 20
Lower to Middle Eocene .......................................................................................................................................... 21 Claiborne Group (Tcb) ...................................................................................................................................... 21 Eocene to Oligocene ........... ... ..... ... ..... ......... ...... .... ......... ..... .. .... .... .... ...................................................... ......... 24 Tertiary Sediments and Residuum (Tsr)............................................................................................................ 24
Post Cretaceous -pre Miocene ................................................................................................................................ 26 K-T breccia/conglomerate (K-Tbx) .................................................................................................................. 26
Miocene ... ..................... ............... ........ .. ............ ..... ..... ......... ........... ........................................................... ............. 29 Altamaha Formation (Ta) ........................ ... ...... .. .. ..... .. .............. ... .... ..................................... .......... .. .. .. ......... ... 29
Quaternary................................................................................................................................................................ 38 Tertiary- Quaternary Alluvium (TQal) ............................................................................................................. 38 Quaternary Alluvium (Qal) ............................................................................................................................... 38
Alteration of primary sedimentary textures and evidence of previous groundwater movement. .............................. 38 Correlation ofSTATEMAP map units with the 1:500000 scale Geologic Map of Georgia .................................... 39 BIOSTRATIGRAPHY............ .............................................................................................. ......................................... . 39 STRUCTURAL GEOLOGY............................................. .............................................................................................. 41 ECONOMIC GEOLOGY ...... ........ ... ............................ ........ .. ................. ........ ............................................................... 44 HYDROGEOLOGY .......................... ............ ...... ........ ........... ............ .... .... .. .................... .... .......................................... 46 Claiborne Aquifer..................................................................................................................................................... 47 Clayton Aquifer.................................................................................,.......................................................,.............. 47 Cretaceous Aquifers ............... ..................................................................................................... .... ................. ........ 48 GEOLOGIC HAZARDS ...................................................................................... ........................................................... 48 SUMMARY ........ .....,... .............................................. ........................................................ .... .. ........... .... ...... ..... .. .... ...... 52 REFERENCES CITED ................................................................................................................................................... 54 APPENDIX ... ................... ........................... ................................................................................................. ................. 59
FIGURES 1. Location of the Lumpkin project area in relation to the most significant recharge areas......................................... 2 2. Map of Georgia showing location of STATEMAP mapping and previous 1:100,000-scale Upper
Coastal Plain geologic mapping. ................ ............................................................. ... ... ............... ....... ..................... 3 3. Stratigraphy and related aquifers in or adjacent to the current map area.................................................................. 4 4. Summary descriptions of the map units in the current map area.............................................................................. 5
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5. Large rounded quartz and quartzite pebbles in a relatively fme-grained, kaolinitic sandstone of the
Providence Formation (Kp) ................. ... ..................... ... .... ..... ..... ...... ................ .... ............. ...... ............ .... .............. 13 6. Unconformity between overlying Miocene age Altamaha Formation (Ta) and strongly altered
kaolinitic sandstone of the Upper Cretaceous Providence Formation (Kp) ............................... ............ .... .... .... .... .. 14 7. Contorted layers of clay residuum of the Clayton Formation (Tel) ........................................................................ .. 15 8. Contact between the overlying sandstone of the Nanafalia Formation (Tnf) and clay and iron oxide
residuum of the Clayton Formation (Tel) ............................................................................................................... .. 15 9. Highly weathered clay residuum of the Clayton Formation (Tel) .. .................. .... ...................... ........ .. .................... 16 10. Kaolinitic clast-rich sandstone of the Nanafalia Formation (Tnf) .. .............. .. .. .......... .. .. ............ ......... .................. ... 18 11. Thin-bedded to massive sandstone of the Nanafalia Formation (Tnf).................. .. .... .. .......... .... ........ ...................... 18 12. West-dipping kaolinitic sandstone of the Nanafalia Formation (Tnf) ...... ....................... ......................... ........ ........ 19 13. Bauxite and kaolin of the Nanafalia Formation (Tnf) .......... ...... .... ...... .... .. ..... .... ........ .... ........... .... ................... .... ... 19 14. Deeply weathered silty clay of the Tuscahoma Formation (Ttu) .............................................................................. 20 15. Thin, thinly-bedded clay cross-cutting cross-bedded sand of the Claiborne Group (Tcb) ....................................... 22 16. Upper contact of the soft Claiborne Group (Tcb) sandstone with the overlying, indurated sandstone of
the Altamaha Formation (Ta) ................................................................................................................................... 22 17. Partially silicified sandstone ledge overlying clay bed in the Claiborne Group (Tcb) ............................................. 23 18. Large petrified log found in borrow pit developed in the Claiborne Group sandstone (Tcb) ........ ..... ..... ....... ......... 23 19. Clay residuum of the Tertiary Sediments and Residuum unit (Tsr) disconformably overlain by the
Miocene age Altarnaha Formation (Ta).................................................................................................................... 25 20. Clay residuum of the Tertiary Sediments and Residuum unit (Tsr) disconformably overlain by the
Miocene age Altamaha Formation (Ta).................................................................................................................... 25 21. Outcrop of unusual conglomerate (K-Tbx) ............... ........ .. ... ...... .... ......... ... .... ......... ..... ... ........ .............. ....... .... .. .... 27 22. Subangular to subrounded clasts of kaolinitic sandstone, sandstone and light gray clay (K-Tbx) ................. .......... 27 23. Unusual conglomerate (K-Tbx) exposed beneath lower contact of the Miocene - age Altamaha
Formation (Ta) ......................................................................................................................................................... 28 24. Unusual conglomerate (K-Tbx) consisting of abundant rounded to subangular kaolin, gray clay/shale,
and sandstone clasts in sandy matrix ........................................................................................................................ 28 25. Channel of the massive, brick-red sandstone of the Altarnaha Formation (Ta) cutting into lighter brown
and reddish brown sandstone of the Providence Formation (Kp)............................................................................. 32 26. Channel of the massive, brick-red sandstone of the Altamaha Formation (Ta) cutting into lighter brown
and reddish brown sandstone of the Nanafalia Formation (Tnf) .............. ............... .. ........... ....... .... ...... ................... 32 27. Two channels of the massive, brick-red sandstone of the Altamaha Formation (Ta) cutting into lighter
brown and reddish brown sandstone of the Nanafalia Formation (Tnf) .............. .......... ... ... ..................................... 33 28. Lower contact of Altamaha Formation (Ta) marked by pebble conglomerate with softer sandstone of
the Claiborne Group (Tcb) ....................................................................................................................................... 33 29. Lower contact ofAltamaha Formation (Ta) marked by boulder conglomerate....................................................... 34 30. Lower contact of Altarnaha Formation (Ta) marked by quartz pebble conglomerate with softer
sandstone of the Claiborne Group (Tcb) .................................................................................................................. 35 31. Lower contact of Altamaha Formation (Ta) marked by quartz and ironstone pebble conglomerate
overlying with softer sandstone ofthe Claiborne Group (Tcb) ................................................................................ 36 32. Lag concentration of ironstone pebbles in roadbed.................................................................................................. 36 33. Brick-red soil derived from the argillaceous sandstone of the Altamaha Formation is prime agricultural
land ... ..... .... ....... .. ....................... ............ ...... ... .... .... ..... .... .... .. ...... .... .......... ........... ... ... ... ........................... ........ 37 34. Rich nature of the soil derived from the Altamaha Formation is illustrated by the lush crops ................................. 37 35. Petrified wood fragments from the Altamaha Formation ......................................................................................... 40 36. Slickensides developed along joints in lower Nanafalia Formation(?) clay ............................................................ 42 37. Right (south) limb of synclinal fold in Nanafalia Formation (Tnf) .......... .. .......... .................................................... 42 38. Left (north) limb of synclinal fold shown in Fig. 37 in Nanafalia Formation (Tnf) ... ............................ ................. . 43 39. Small scale fold in interbedded clay and sandstone in the Claiborne Group ............................................................ 43 40. Flooded open pit of the Gamer mine that was operated about 1916 .... ....................... .... .............. ........ ................... 46 41. View of the flooded open pit of the Gamer mine (Smith, 1929) ............ .. .................. .. .................... ........................ 46 42. View of erosion gully shown in next picture from bottom of gully................................. .......... ............ ................... 50 43. Head of erosion gully shown in preceding photo approaching road......................................................................... 51 44. Apparent initial road failure with fracture arcs focused at head of erosion gully in Claiborne Group
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sandstone .................................................................................................................................................................. 51 45. Erosion gullies develop as sites for dumping of potentially hazardous materials and contamination of
aquifers ................................................................................................................................................................... 52 TABLES 1. Percentage of quadrangle containing map unit polygons .......................................................................................... 10 2. Geochemical analysis of GGS# 4084 ....................................................................................................................... 45 3. Chemical analysis of bauxitic clay and bauxite interval from hole 87 ............ ............ ........ ................... .................. 45 4. Chemical analysis ofbauxite from the Springvale district ....................................................................................... 45 5. Aquifer characteristics in the study area................................................................................................................... 48 PLATES 1. Geologic map of the Georgetown 7.5 minute quadrangle. 2. Geologic map ofthe Cuthbert 7.5 minute quadrangle. 3. Geologic map of the Brooksville 7.5 minute quadrangle. 4. Geologic map of the Martins Crossroads 7.5 minute quadrangle. 5. Geologic cross-sections
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INTRODUCTION
Scope of the mapping project
The Georgia Geologic Mapping Program mapped the surface geology of the Brooksville, Cuthbert, Georgetown, and Martins Crossroads 7.5minute (1:24,000 scale) quadrangles in the Upper Coastal Plain of southwestern Georgia from October, 2005 through June, 2006. 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 Mapping Program's STATEMAP Project (in cooperation with the United States Geological Survey, Cooperative Agreement #05HQAGOOI6).
The Georgia Geologic Mapping Program's STATEMAP Project involves the geologic mapping of significant aquifer recharge zones in the Upper Coastal Plain (Fig. 1). These recharge zones include those of the Cretaceous, Clayton, Claiborne, and Upper Floridan aquifers. Previously funded STATEMAP mapping in Georgia (Fig. 2) included 18 quadrangles of the Americus area and compilation of that mapping as a 1:100,000 scale geologic atlas of the Americus area. In the Lumpkin project area, three quadrangles were mapped in 2004. Figure 3 provides a summary of the stratigraphy and related aquifers in or adjacent to the Lumpkin project area.
Methods
Field methods used to produce the geologic maps (Plates 1 through 4) involved mainly the description and mapping of roadside outcrops and exposures. In addition to the geologic mapping, 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 5. The Georgia Geologic Mapping Program drilled a series of shallow core holes (less than or equal to 50 feet) that were designed to: 1) confirm the mapped geology, 2) determine depth to contacts, and 3) examine relatively non-weathered lithologies particularly in areas with limited exposures.
A significant part of this project involved production of digital mapping products. Outcrop locations were digitally plotted directly from field maps using Arcinfo 9.1. Additional field geologic data were compiled in an Arclnfo database. Digital geologic maps were compiled on-screen using the outcrop data and cross-sections (Plate 5). Arcplot programs were written to prepare hard copies of each individual geologic map (Plates 1 - 4). 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 Arcinfo export files of those coverages are in preparation. Development of the Arcinfo 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 portion of the Lumpkin STATEMAP Project generally follow that of Cocker (2003b; 2004), Eargle (1955), Hetrick (1990), Marsalis and Friddell (1975), and Reinhardt and others (1994).

Tennessee
Florida
Figure 1. Location of the Lumpkin project area in relation to the most significant groundwater recharge areas. The most significant groundwater recharge areas are shaded.
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LXPLANATION

Map coverage @ l:l 00,000 scale

Wrens-Augusta (GGS, Hetrick, 1992)

Kaolin District (GGS. Hetrick and Frid.dcll, 1990)

Fort V.llley (GGS, Hetrick, 1990)
Iii Butler (GGS, Hetrick, 1996)
~- : Americus 30' x 60' (USGS. Reinhardt and others. 1994)
Map coverage@ I:24,000 scale
0 Americus Project- STATEMAP (completed 2003)



Lumpkin Project- STATEMAP

N
l

Sca le (1lPJlfO:-:ima lc.) (.__ _ _s_(,J mile.~

Figure 2. Map of Georgia showing location of STATEMAP mapping and previous 1: 1000,000-scale Upper Coastal Plain geologic mapping.

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Period
Quaternal)'

Epoch
Recent Pleistocene
Miocene

Eocene to Oligo.:cne

Formation
unmmted stJcam alhtl'ium unn~d stream alluvium
Altanmlm Format.ion
Residuum from Eac.:me and Oligoc.ene limestones. M1y include units as old l\S lhe Lisbon Fommlion

Group
Vicksburg Group

Aquifer

Tertiary

Eocere

Ocmltlgee l'l~rmation IHI/i~tolt Fnmmtion Jluckalee Formation
Clinchjield Formation
Perry .'W:mr/i Lisbon Formation Tallal-ntta Formation
HatcJuuigbee Formar.ion

OcnlaGroup

Upper
Floridan Aquiter

Bamwell Group C:laibomc Group

Claibomc Aquifer

Tuscaooma Fonnation

\Vilco.x Group

Palcoccr.::

Nanafillill Fonnalion
Poriers Creek formation Clayton Fonnation

.Midway Group

Clayton Aquifer

Provide11ce Pomlation

Providence Aquifer

Cretaceous

Gulrian

RipkJ' Fonnation Cus.<>eta Sand BlutTtown Fonnation
Eutaw Fonmnion

Scln1<1 Group Eutnw Group

Cussctn Aquifer
EutawBlufflown
Aquifer

Tuscaloos:1 Ponnalion

Tuscaloosa Group

Co mane bean

Undificrentiatcd

F1g. 3. Stratigraphy and related aquifers m or adJacent to the current map area.(* Upper part ofTuscahoma Fonnation may be Lower Eocene in age). Units in italics are absent or not recognized as distinct, mappable units.

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Map

1 j"'

Unit

I Symbol

""



~ e ~

'z:=i:;::l;

Qal

;!!
g

Cl

! .; 'I)
~ ~ 1)
~ ~ z:;:;~

Ta

j ~.~~-
..::HS

Tsr

c ~
.. ~ '=li
l ~

..':l_
= g

J,ol

:~g

Tcb

~ ~~
1--

r~:: ~

jtll

Ttu

!"'""-

. ~

g '5 ~ ~ ~

oi~ ~ !i:~

Tnf

~

~

i

Tpc

"r:.>i..l..
-.~s ;'5"=a'

Tel

~

Kp

2

lil
u E

Kr

t

8:
~

Kc

Unit Description
QWitt'ntlU'' alluvium variably micaceous and clayey, poorly-sorted, ~ill, sand. and quartz gravel.
Alt:.urulflll Fonnation - domillDnlly 11lll$shc, brillk-rcd. ;u--gillac.x>us Sllndl.tone and mottled clay-rich sandstones with p;:n to cohbl~ (rurc:.) sizool irunst tl.! ..:la~ts. tUlCOmmun ljllarfl. JXlhhlc:. b~ds. and rnr.: ch~l cl :ll>1s. Conglomcru\ic layer .::ommonly found ut low.:r contocr with CluibQmc Group sand!! c<mtnin~ ironstone clast~ and quw1l. ~bb1.:. . 1111d IOCllUy irou oxide cn.ISis :md round~< cobble to bouldcr-siz.OO clasts uf snndstoue apparently derived from aosiou of underlying Claihome Group S<ldiments. Tt>rtbey Sedlnw.mts and ReslcllMllll- variably wa.''Y to slightly silty clays that commonly include abundant cht .
~moved by erosion or not recognized; may be part oftl~e Tertia!)' Sedintotn!S and Residuum.
Oolbo~ (~rtltlp:
Pel"Q' S111td line- to collffl.:-grained, massi,c to cross-b<:dd.:d . and l.'~ding downdip to Lisbon Foonation. lbbon Fonn11 tlon c. tcarcou s. s~dy day. d aycy ~nod. nnd lim tot~ Toll:lhalb Fonnallon mM>~ iw- ro eros. -bedded, fllk' to .:oan;c-grninc:d. {incly lay.:r~d to <:CQSSb<:ddcd 1i'l!ld and l!<'UldstOM ittte rlaye.r~-d wit[! two ~lin shot.::s to stutdy shAles. P.:cry Sumi may be o.\tJUivalo!at to Tall ahallu Fonuation. TWI4"llhOOI.a flonnatlon- nonfossilifc:rous, carbonaceous, clay, sill, and sand overlying and laterally grading iuto cro -b.:ddtld. mi.:a.:eous. cakateot!S. fossiliferous. medillln 10 coarse-grained saud. Nanatidia Fqrmati011 micaceous, mru;.<;i\e-b.:dded, glauconitic, fos~ilif.:rous. calcareOUJ'l. tine- to c<.>ar~e-grained sand with local clny knocs.
Porters Creek Fomaation f<n-~iliferous, glauconitic. f~~"' ile. waxy to variably silty clay.
C1ayton Fot'lltld!ou sa~dy. micritic, bioclastic limestone with inter-blld<kd silty clay and calcareous sand<ltone .
Providm. Fonnatmn- koolinitic. cross-bedde<l medilan- coarse-grnin.OO Sll!ld and sandstone with locul k..'IOlin lenses Ripley Fomlatkm m~sho:. micaceous and glaucooitic. fine gt11in.:d sand and $illy cla y Cusseta Fonnatlon cross-bedckd. locally kaoliniti.:, medium to conrse-~ooraine<l sand

Kb

Blumown Fonnotion- glauconitic. .:alcareous, fin~ sand overluin by cnrb01tllCOOll'< clay attd silt. cross-beddo!d

sand and hi!!hlv fos~iliferou~ clav to l'ianc<mitk fine sand

Figure 4. Summary descriptions of the map units in the current map area.

Previous investigations

Recent regional scale maps (1:100,000) are located in relation to the STATEMAP quadrangles in Fig. 2. The quadrangles mapped during this current project are adjacent to the Twin Springs, Sanford, County Line, Benevolence and Shelhnan 7.5' quadrangles (Cocker, 2001, 2004a, 2005b).

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The Geologic Map of Georgia (Georgia Geologic Survey, 1976) and the 1:500,000 scale Digital Geologic Map of Georgia (Cocker, 1999) provide a general view of the surface geology of the map area. Digital overlays of the geology and topography @1 :24,000 scale display a rough correlation between the 1:500,000 scale geology of the state map and the detailed topography.
Other geologic investigations in or near the present map area are concentrated mainly on the stratigraphic sections exposed along the Chattahoochee River that were exposed prior to flooding of the Walter F. George Reservoir. Geologic reports that provide pertinent information or aid in interpretation to the present mapping include local and regional studies by Beck (1982), Bybell and Gibson (1982), Cocker (2001, 2002, 2003a, b, 2004a, b, 2005a, b), Cocker and Costello (2003), Cramer and Arden (1980), Eargle (1955), Fallaw and Price (1992), Fritz (1989), Gibson (1982), Gohn and others (1982), 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), Kirkpatrick (1959, 1963), Marsalis and Friddell (1975), Nystrom and Willoughby (1982), (Owen (1956), Reinhardt (1982, 1986), Reinhardt and Gibson (1981), Toulmin and LaMoreaux (1963), and Zapp and Clark (1965).
Few deep drill holes are available for the present map area. Subsurface geologic investigations of the study area include descriptions of well logs and hydrologic reports. Lithologic descriptions of core samples and cuttings from wells in Quitman and Randolph Counties were obtained from published data by Herrick (1961), and unpublished drill logs by Herrick and anonymous authors (Georgia Geologic Survey technical files, Atlanta, Georgia). Many core logs and stratigraphic determinations (if present) are not of sufficient quality and consistency for constructing . accurate cross-sections. Clarke and others (1983, 1984), Gorday and others (1997), Johnston and Miller (1988), Long (1989), McFadden and Perriello (1983), Mitchell (1981), Reinhardt (1982), and Vorhis (1972) examined the hydrology and hydrogeology of the region.
Soil characteristics vary considerably over the mapped area. Those soils derived from poorly cemented sands and silts such as the Tallahatta Formation of the Claiborne Group and the Providence sand are prone to rapid erosion. Clay- or silt-rich stratigraphic units, e.g. the Tertiary sediments and residuum unit, the Tuscahoma Formation and the Ripley Formation, yielded poor clayey soils. The Altamaha Formation is a mixed sand and clay unit overlying much of the eastern part of the map area, and yields a rich loam type of soil. Soils developed on the floodplain sediments of the Chattahoochee River are relatively rich, also.
PHYSIOGRAPHY AND LAND USE
The Brooksville, Cuthbert, Georgetown, and Martins Crossroads quadrangles lie within the Coastal Plain Physiographic Province. Terrain in the Brooksville, CUthbert, and Martins Crossroads quadrangles is relatively flat with relatively deeply incised valleys of the Little Ichawaynochaway Creek, Pachitla Creek and their tributaries. West and north of CUthbert, tributaries of Pataula Creek have cut down considerably into the upper part of the soft Cretaceous sediments. Physiography in the Georgetown quadrangle is dominated by the Chattahoochee River and its short tributaries (Bustahatchee, Soapstone, Tobanee, and Smithee Jack Creeks) and is best described as very hilly with few flat areas. The larger flat areas are found adjacent to the Chattahoochee River in the northern part of the quadrangle and underlying Georgetown in the southern part of the quadrangle. Flat bottomland in the major stream valleys is commonly sandy and marshy, and is ill-suited for either development or agriculture. Stream valleys are
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generally wide and flat, typically on the order of 0.15 to 0.4 miles wide, with relatively steep slopes. The Chattahoochee River valley is on the order of 1.5 miles wide. Current base level in the Chattahoochee River valley is about 200 feet because of the Walter F. George Reservoir. Stream valleys gradually descend from 370 to 250 feet from the northwestern part of the Brooksville quadrangle to the southern part of the Martins Crossroads quadrangle.
The hilly terrain is characteristic of the Fall Line Hills physiographic district. An escarpment that extends southwesterly through the Cuthbert quadrangle reflects breaching of the Altamaha Formation caprock and rapid down cutting through the Claiborne Group. Most of the terrain in the Georgetown quadrangle is between 200 and 450 feet. The few areas up to 560 feet are underlain mainly by remnants of the Altamaha Formation. In the three eastern quadrangles, the highest interfluve area is about 550 feet in the northwestern part of the Brooksville quadrangle, and this interfluve area gradually descends to about 350 feet in the southeastern part of the Martins Crossroads quadrangle. Much of the upland interfluve area in the eastern half of the Cuthbert quadrangle and most of the Brooksville and Martins Crossroads quadrangles are covered by a relatively thin 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 Claiborne Group.
Streams west of the Cuthbert escarpment flow into the Chattahoochee River. In the Cuthbert quadrangle Holanna Creek, which empties into Pataula Creek, has a base level on the order of270 to 300 feet., Base level of the Chattahoochee River flood plain is on the order of 195 to 200 feet, because of the Walter F. George Reservoir. The relief in the Georgetown quadrangle, on the order of350 feet, is extreme.
Because of the hilly terrain and generally poor soils in the Georgetown and western part of the Cuthbert quadrangles, agriculture, with the exception of tree harvesting, is generally not an important industry. Large tracts of land in the Georgetown quadrangle may be leased or owned by hunting clubs. The floodplain of the Chattahoochee River is being utilized for agriculture. Agriculture is important in the relatively flat interfluve areas in the eastern part of the Cuthbert quadrangle and much of the Brooksville and Martins Crossroads quadrangles. Agricultural products may include pasture, cotton, pecans, beefcattle, sawlogs and pulpwood.
The major population centers include Cuthbert and Georgetown.
SOILS
In the Georgetown quadrangle, flat land best suited for agriculture is present along the Chattahoochee River. Soils along the Chattahoochee River are derived mainly from the Cusseta Formation and various alluvial materials. Much of the remaining area is underlain by poor, generally sandy soils derived from the Cretaceous age sedimentary units. In the eastern part of the Cuthbert quadrangle and over much of the Brooksville and Martins Crossroads quadrangles, broad expanses of relatively flat land are utilized for pecan orchards, farming, and cattle. These broad expanses are mainly underlain by the Altamaha Formation with smaller areas underlain by the Tertiary sediments and residuum unit and the Claiborne Group. The argillaceous sandstone of the Altamaha Formation provides the best soils suited to agriculture. Areas underlain by clays of the Tertiary sediments and residuum unit and sands of the Claiborne Group are best suited for orchards, pasture and forest products.
Soils in the map area reflect intensive subtropical weathering of the exposed Tertiary and Cretaceous stratigraphy Soils may be classified based on diagnostic surface horizons, epipedons, and subsurface horizons. The
7

principal 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 defmed as a subsurface accumulation of high-activity silicate clays that have moved downward or translocated from the upper horizons or have formed in place (Brady and Weil, 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 cationholding capacities (< 16 cmolJkg 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 Weil, 1999).
Intensive subtropical weathering has produced a commonly striking profile in the soils and subsoils, particularly in those derived from the Altamaha Formation. The upper portion of the profile is commonly sand-rich or slightly argillaceous sand/sandstone. This portion of the profile may range from 0 to 5-10 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 related to oxidizing ground water, is usually developed in the clay rich lower zone. Irregular concentrations 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 (2001) described and interpreted the vertical distribution of particle sizes in the main soil types of the Bottsford, Dawson, Parrott and Shellman quadrangles just to the east of the current map area. These relationships should generally exist in the Cuthbert, Brooksville and Martins Crossroads quadrangles where the Altamaha Formation is located.
GENERAL GEOLOGY
The surface geology of these four quadrangles is quite varied, with mainly Eocene and younger Tertiary sediments exposed over most of the Brooksville and Martins Crossroads quadrangles, and the eastern portions of the Cuthbert quadrangle. Lower Tertiary sediments dominate the western part of the Cuthbert quadrangle and Upper Cretaceous sediments are dominant in the Georgetown quadrangle. Younger sedimentary rocks are dominant to the east because of the regional southeasterly dip and the land is progressively topographically higher to the east. Erosional unconformities, facies changes, surface weathering, groundwater 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 quadrangles.
As in the area covered by the Americus geologic atlas (Cocker, 2003b), 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 the residuum of Eocene and Oligocene age sediments, represented mainly by clay and chert, are found in the Brooksville, Cuthbert and Martins Crossroads quadrangles.
8

Generally soft, unconsolidated or poorly cemented sandstone of the Middle Eocene Claiborne Group is found on slopes and on locally large portions of the upland areas in the Brooksville, Cuthbert and Martins Crossroads quadrangles. The Upper Paleocene Tuscahoma Formation is found in valley bottoms in the Brooksville and Martins Crossroads quadrangles and on slopes in the western part of the Cuthbert quadrangle. Apparent local and probably regional variations in thickness are evident in the Tuscahoma Formation and Claiborne Group. Kaolinitic, micaceous, cross-bedded sandstone of the Upper Paleocene Nanafalia Formation is found to crop out in the Cuthbert quadrangle and perhaps in the Georgetown quadrangle. A clay and iron oxide residuum of the Lower Paleocene Clayton Formation lies discontinuously above the Providence Formation and is generally poorly exposed.
Progressively older Upper Cretaceous rocks are exposed in the northern and western parts of the current map area. Kaolinitic, micaceous, cross-bedded sandstone of the Upper Cretaceous Providence Formation is found over much of the Georgetown quadrangle and in the Cuthbert quadrangle where tributaries of the Chattahoochee River have cut through the overlying Tertiary sediments. Soft, fossiliferous clay, silt and marl of the Ripley Formation are found in the northern valleys of the Georgetown quadrangle above soft sandstone of the Cusseta Formation. Subsurface information regarding the Upper Cretaceous stratigraphic section is sketchy within the present map area and thicknesses of these units are poorly known in this area.
Regional dip of the Upper Cretaceous and Tertiary sediments older than the Altamaha Formation is on the order of 10 to 30 feet per mile to the southeast. Locally, sediments and contacts dip to the north and west and may reflect reversal of dips caused by folding. Folds are particularly evident in the northwestern part of the Cuthbert quadrangle. 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. Total thickness of the Upper Cretaceous section is unknown, because of the lack of deep and detailed drill hole data. The Tertiary section increases in thickness from the west and north to the south and east (Plate 5). The Upper Cretaceous section is at least 1830 feet thick in the Georgetown quadrangle. Maximum thickness of the Tertiary section in the southeastern part of the map area is on the order of 400- 500 feet.
A summary of map unit areas for each quadrangle (Table 1) indicates significant differences in the geologic makeup of each quadrangle. The bedrock of the Georgetown quadrangle is mainly composed of the Ripley and Providence Formations (nearly 70%). The Brooksville and Martins Crossroads quadrangles are dominated by the Altamaha Formation and the Claiborne Group (about 84 %) with a lesser amount of the Tuscahoma Formation (about 7.5 %) in the Brooskville quadrangle. In the Cuthbert quadrangle, the Altamaha Formation and the Claiborne Group (54 %) dominate in the eastern part of the quadrangle with the Tuscahoma, Nanafalia, and Providence Formations being more widespread in the western part. Also, several Tertiary-age unconformities appear to have removed some or all of the pre-Miocene Tertiary sediments. An increasingly larger portion of alluvium is apparent in these quadrangles as compared with those quadrangles mapped further to the east. The large, flat bottomed creeks and the wide valley of the Chattahoochee River contribute to the larger importance of alluvial material (6 - 12 % of the map area.
Geologic cross-sections
Because of relatively few reliable well logs for those wells within the map area, construction of the geologic cross-sections depended primarily on mapped field relations.
9

Table 1. Percentage of quadrangle containing map unit polygons. Data is derived from Arclnfo databases created for each quadrangle's geologic map. Numbers are estimates at best because ofm1certainties in the geologic mapping. The Georgetown data are only for that portion of the quadrangle within Georgia.

Water
Quaternary Alluvium
Tertiary-Quaternary Alluvium
Altamaha Formation
Tertiary Sediments and Residuum
Claiborne Group
Tuscahoma Formation
Nanafalia Formation
Clayton Formation
Providence Formation
Ripley Formation
Cusseta Formation

Brooksville 0.59% 6.72%
52.55% 1.26% 31.24% 7.63%

Cuthbert 0.27% 8.26%
28.16% 2.51% 26.55% 9.36% 19.20% 3.80% 1.90%

Georgetown 9.62% 9.72% 1.17% 5.95%

Martins Crossroads
0.33% 11.74%
59.99 2.95% 24.80% 0.20%

0.58% 52.94% 16.59% 3.10%

Accuracy of well locations is highly variable. Most of these wells were drilled for water supply purposes, and some were apparently not surveyed. Prior to the 1970s, 7.5 minute quadrangle maps were not yet available for this part of Georgia, and well locations were marked on Georgia Department of Transportation coWlty 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) coWlty road maps which are located in the Georgia Geologic Survey technical files. Well locations were then plotted on digital images of each DOT coWlty road map, and attributes were added in ArcView.
Another GIS database was developed from an earlier, Wlpublished digital database of GGS numbered wells that were located by latitude and longitude. A digital plot of both of those databases together show some of the same wells from each database to lie 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 the more accurate database. Actual locations of these older wells still could be several hWldred feet from the positions plotted on the accompanying geologic maps, as the precision of the latitude and longitude data does not allow a more accurate plot.
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 are shown on Plates 1, 2, 3, and 4.

10

STRATIGRAPHY OF THE BROOKSVILLE, CUTHBERT, GEORGETOWN AND MARTINS CROSSROADS QUADRANGLES
Exposed stratigraphic units in the study area include the Upper Cretaceous Cusseta (Kc), Ripley (Kr) and Providence (Kp) Formations, Paleocene Clayton (Tel) and Nanafalia (Tnf) Formations, Upper Paleocene Tuscahoma Formation (Ttu), Middle Eocene Claiborne Group (Tcb), the Miocene Altamaha Formation (Ta), Tertiary-Quateranry Alluvium (TQal), and Quaternary Alluvium (Qal). An additional map unit, the Tertiary Sediments and Residuum unit (Tsr), is believed to consist of unidentified portions of Eocene and Oligocene stratigraphic units and their residuum. Descriptions of these units are summarized in Figure 4.
Upper Cretaceous Exposed Upper Cretaceous sediments in the map area include the Cusseta, Providence and Ripley Formations.
Recent studies of the Upper Cretaceous sediments from eastern Alabama to the Flint River indicate that most of the Upper Cretaceous units contain two or more lithofacies (Rheinhardt and Gibson, 1981). These include a continental facies and a marine facies. Generally, the basal and downdip portions of these units are representative of the marine facies.
In addition, asymmetrical depositional cycles composed of regressive and transgressive phases are developed in the Upper Cretaceous sediments (Rheinhardt and Gibson, 1981). The regressive phases representing progradation are thicker and better developed. Progradation may be due to sedimentation rates greater than basin subsidence or to a gradual drop in sea level. Descriptions of the lithologies and their depositional environments are discussed in Rheinhardt and Gibson (1981).
Selma Group Cusseta Formation (Kc)
In updip areas, the Cusseta Fonnation consists of 170 to 235 feet of coarse, Ophiomorpha-bearing generally cross-bedded sand (Rheinhardt and Gibson, 1981; Rheinhardt and others, 1984). This description differs from that of Marsalis and Friddell (1975) who indicate that the Cusseta Formation consists of 185 feet of irregularly crossbedded, coarse-grained to gravelly sands containing kaolin balls and small kaolin lenses. According to Rheinhardt and Gibson (1981) and Rheinhardt and others (1984), grain size, the amount of sand and scale of cross-bedding decrease downdip. Towards the upper contact with the Ripley Formation, thinly bedded carbonaceous clay becomes more abundant. The updip portions of the Cusseta Formation represent deposition in a relatively stable barrier island complex. The upper sediments represent deposition in a restricted back barrier environment during a regressive sea level change (Rheinhardt and others, 1984). Over much of the area mapped as Cusseta Formation in the Georgetown quadrangle, topography consists of numerous low hills probably reflecting the relatively poorly consolidated nature of these sediments. Exposures are generally poor.
11

Ripley Formation (Kr)
The lower part of the Ripley Fonnation consists of a massive, bioturbated, fme to medium grained, micaceous, glauconitic, calcareous quartz sand. The upper part of this unit is commonly massive, fme sand to silty clay. Near the top of the Ripley Fonnation, grain size increases abruptly, may contain a bone and shell lag, and is well bedded. Thickness of the Ripley Fonnation ranges from 135 feet up dip to 250 feet downdip (Reinhardt and others, 1994). Generally, the Ripley Fonnation is a relatively fossiliferous unit. Older sediments of the Ripley Fonnation were deposited in an inner shelf environment. Younger sediments were deposited in a barrier island complex. The top of the Ripley Fonnation was marked by abrupt shallowing and subaerial exposure with development of paleosols (Rheinhardt and others, 1994). In the Georgetown quadrangle, sediments mapped as the Ripley Fonnation are generally poorly exposed. Cliffs along the Walter F. George Reservoir have good exposures of the marly portion of the Ripley Formation. Lack of a boat and operator prevented a careful inspection of these exposures.
Providence Formation (Kp)
The Providence Fonnation is the youngest Upper Cretaceous unit in the current map area. Reinhardt and others (1994) describe the Providence Fonnation as pale yellow, cross-bedded, locally micaceous, fme to coarse sand with inter-bedded, yellowish brown to olive, massive to thinly bedded, sandy clay lenses. This unit is subdivided in crosssections into two lithofacies. The up dip lithofacies consists of cross-bedded, coarse quartz sand with locally abundant heavy minerals. The heavy mineral suite consists mainly of ilmenite, zircon and rutile and locally may constitute up to one third of the sand (Rheinhardt and Gibson, 1981). The down dip lithofacies is a laminated to massive, highly micaceous, locally carbonaceous, silty clay and clayey fme sandstone. Both lithofacies may be burrowed or bioturbated. The up dip lithofacies was divided into an upper and lower cross-bedded sand by a 20 inch thick sandy clay bed (Donovan, 1985). Thickness of the Providence Fonnation may range from 83 to 267 feet (Marsalis and Friddell, 1975; Reinhardt and others, 1994). Kirkpatrick (1959) described the Providence Fonnation as being 140 to 160 feet thick.
An outcrop near the base of the Providence Formation contained abundant large rounded quartz and quartzite clasts (Fig. 5). An upper contact of the Providence Fonnation with the Altamaha Fonnation is locally marked by strong alteration (mottling) of the Providence Fonnation (Fig. 6). The mottling occurred prior to deposition of the Altamaha Fonnation.
The basal Perote Member is 10 to 35 feet thick and consists of thinly bedded, dark-grey, highly micaceous and lignitic, sandy silt and clay. This grades upward to fme sand and eventually to medium to coarse, cross-bedded sands of the upper member. Donovan (1985) and Reinhardt and others (1994) consider the Perote Member to be the upper part of the Ripley Fonnation. Marsalis and Friddell (1975) described the Perote Member as the basal part of the Providence Fonnation. The upper member of the Providence Fonnation consists of variegated white to yellow to orange, micaceous, feldspathic, cross-bedded, medium- to very coarse-grained sand (Marsalis and Friddell, 1975).
Induration of the Providence Fonnation varies considerably from relatively hard sandstone, to soft sandstone, to soft sand/sandstone. Headward erosion into the generally soft sand and sandstone of the Providence Fonnation has cut steep, cliff-like scarps. Most of this erosion is related to rapid downcutting by streams in the Chattahoochee
12

River Basin (Cocker, 2005). Trace fossils consisting of clay-lined, Ophiomorpha burrows are locally abundant in cross-bedded sandstone
(Rheinhardt and Gibson, 1981) and are classified mainly as belonging to the Skolithos ichnofacies (Frey and Pemberton, 1984). These Skolithos ichnofacies are indicative of relatively high levels of wave or current energy, typically developed in clean, well-sorted, loose or shifting particulate substrates (Frey and Pemberton, 1984). The occurrence of this ichnofacies with large and small-scale trough cross-bedding indicates a near-shore environment such as on the foreshore and shoreface of beaches, bars and spits (Frey and Pemberton, 1984). These burrows are usually developed in soft sand and do not weather well.
Figure 5. Large rounded quartz and quartzite pebbles in a relatively fine-grained, kaolinitic sandstone of the Providence Formation (Kp). Georgetown quadrangle.
13



~J

Figure 6. Unconformity between overlying Miocene age Altamaha Formation (Ta) and strongly altered kaolinitic

sandstone of the Upper Cretaceous Providence Formation (Kp). Upper red rocks are part of the Altamaha

Formation. Georgetown quadrangle.

Lower Paleocene Midway Group Clayton Formation (Tel) The Clayton Formation is described as being composed of yellow to buff-brown, interbedded, micaeous silty
clay, calcareous sandstone, and bioclastic limestone (Reinhardt and others, 1994). The limestone is described as locally well-crystallized and well-cemented or vuggy and is composed of molluscan and bryozoan fragments. In the Chattahoochee River area, the Clayton Formation is described as: I) a basal conglomerate overlain by interbedded grayish-yellow sandy, shelly limestone and calcareous sands; 2) a white to gray, dense limestone with oyster shells and other fossil debris; and 3) an upper white to gray microfossiliferous, massive limestone (Cramer and Arden, 1980; Marsalis and Friddell, 1975; Toulmin and LaMoreaux, 1963). Observations made at Ft. Gaines Chattahoochee River exposures are of a rhodolithic limestone.
In the present map area, the Clayton Formation is represented principally by a residuum of red, buff to dark brown, white to light gray and black clay with layers and irregular masses of iron oxide (Fig. 7, 8 and 9) and iron oxide-cemented sandstone.

14

Figure 7. Contorted layers of clay residuum of the Clayton Formation (Tel). Georgetown quadrangle.
Figure 8. Contact between the overlying sandstone of the Nanafalia Formation (Tnf) and clay and iron oxide residuum of the Clayton Formation (Tel). Cuthbert quadrangle.
15

Figure 9. Highly weathered clay residuum of the Clayton Formation (Tel). Cuthbert quadrangle. Strongly distorted bedding also suggests collapse due to dissolution of carbonates (Figs. 7 and 8). The
distribution of weathered Clayton residuum generally north of Pataula Creek and mainly unweathered limestone and shale south of this creek suggests that the southern part of the Clayton Formation was generally exposed to little or patchy weathering prior to deposition of the Nanafalia Formation. Irregular, small to large masses of iron oxide (goethite ?) are commonly found in the Clayton Formation (Fig. 8) and were of sufficient extent and grade to have been mined for their iron content in the area to the north of the current map area (Cocker, 2004, 2005).
Present mapping suggests that the Clayton Formation is discontinuous and quite variable in thickness. In crosssections (Plate 5), the thickness of the Clayton Formation is based mainly on well log data in the down dip areas and is idealized. Minimum thickness in drill hole GGS #552 is 120 feet. Up dip portions of the Clayton Formation are probably quite variable in thickness and distribution. Extensive karstification and erosion may have removed some or all this unit prior to deposition of the Nanafalia Formation. Regionally, thickness of this unit may range from 10 to 165 feet (Marsalis and Friddell, 1975; Owen, 1956; Reinhardt and others, 1994). The variability in thickness and regional thinning of the Clayton as depicted in cross-sections by Rheinhardt and others (1994) may be a better representation.
16

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 (Reinhardt and others, 1994). Thickness of this unit, where present, is 3 to 33 feet. If this clay is present in the current map area, it could not be distinguished from the clay and residuum of the Clayton Formation and is included as part of the Clayton Formation.
Upper Paleocene to Lower Eocene Wilcox Group Nanafalia Formation (Tnj)
In the current map area, the Upper Paleocene Nanafalia Formation is exposed mainly in the Cuthbert quadrangle and perhaps in the Georgetown quadrangle. The Nanafalia Formation consists of cross-bedded, fine to very coarse, light greenish-gray to yellowish-brown to white, highly micaceous quartz sandstone, kaolin and bauxite (Figs. 10, 11, 12, 13). Black, heavy mineral sands are locally concentrated in the road gutters. The sandstone may contain abundant, rounded or subrounded kaolin or bauxite clasts (Fig, 10).
Because of poor exposure, the Nanafalia - Clayton Formation contact and the Nanafalia - Tuscahoma Formation contact were seldom observed in the current map area. Exposures in the County Line quadrangle shows channels of Nanafalia Formation sandstone cut into relatively fresh shale/clay of the Clayton Formation (Cocker, 2005b). Significant erosion since deposition of the Nanafalia Formation has removed or cut deeply into the Nanafalia Formation in a number of exposures.
The Nanafalia Formation is divided into two coeval lithofacies, the Baker Hill and Nanafalia Formations (Reinhardt and others, 1994). The Baker Hill Formation is described as consisting of 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 may contain sand or silt laminae. Scattered thick lenses of kaolin contain bauxite. The Gravel Creek Member, the marginally marine to nonmarine facies of the Nanafalia Formation (Huddlestun and others, 1974), is similar to the Baker Hill Formation of Reinhardt and others (1994).
According to Reinhardt and others (1994), the Nanafalia 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. Reinhardt and others (1994) note that the Nanafalia Formation may be 20 to 160 feet thick. Large, economic deposits of kaolin and bauxite are found in the Nanafalia Formation in the Andersonville, Springvale and Eufaula districts.
17

Figure 10. Kaolinitic clast-rich sandstone of the Nanafalia Formation (Tnt). Cuthbert quadrangle.
Figure 11. Thin-bedded to massive sandstone of the Nanafalia Formation (Tnt). Thin-bedded clay on the extreme right of the roadcut may be the marine facies of the Nanfalia Formation, the Porters Creek Formation or the Clayton Formation. View is to the north with bedding orientation ofN 15 Wand dipping 49 W. East limb of syncline. Cuthbert quadrangle.
18

Figure 12. West-dipping kaolinitic sandstone of the Nanafalia Formation (Tnf). Bedding orientation is N 12 Wand 15 W. Cuthbert quadrangle.
Figure 13. Bauxite and kaolin of the Nanafalia Formation (Tnf). Cuthbert quadrangle. 19

Tuscahoma Formation (Ttu) The Upper Paleocene Tuscahoma Formation is generally poorly exposed in the map area (Fig. 14). The Tuscahoma Formation consists of non-fossiliferous, gray, inter-laminated clay, silty clay, and fine quartzose sand. Drilled thickness of the Tuscahoma Formation in the Benevolence quadrangle (Cocker, 2004a) is on the order of 50 feet, but may be thinner or absent, due to erosion prior to the deposition of the Claiborne Group and Altamaha Formation. According to Marsalis and Friddell (1975), the Tuscahoma Formation near the Chattahoochee River, consists of90 to 153 feet ofnonfossiliferous, gray, inter-laminated clay, silty clay, and fine quartzose sand. Reinhardt and others (1994) indicate the Tuscahoma is composed of 10 to 60 feet of dark greenish-gray 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.
Figure 14. Deeply weathered silty clay of the Tuscahoma Formation (Ttu). Brooksville quadrangle. Hachetigbee Formation - Bashi Marl Member
No outcrops of the Hatchetigbee Formation were identified during the current mapping. Reinhardt and others (1994) describe the Hatchetigbee Formation as generally less than 25 feet of light to dark greenishgray, dominantly massive, well-sorted, very fine- to fine-grained quartz and glauconite sand. This unit contains intervals of interbedded and inter-laminated clay, silt and very fine quartz sand. Marsalis and Friddell (1975) found the Bashi Marl to be discontinuous along the Chattahoochee River.
20

Lower to Middle Eocene Claiborne Group (Tcb) The Claiborne Group is a thick, generally sandy unit that, in the current map area, lies between the
Tuscahoma Formation and the Altamaha Formation and/or the Tertiary Sediments and Residuum unit. Sandy ~ediments in this stratigraphic interval which are found in this part of Georgia's Coastal Plain have normally been referred to as the Tallahatta Formation (Marsalis and Friddell, 1975). These sediments are equivalent to those sandy sediments classified as the Claiborne Group in the Americus geologic atlas (Cocker, 2003) and in the Benevolence quadrangle (Cocker, 2004) to the east of the present map area.
The Claiborne Group is generally not well exposed in the current map area. Outcrops are in steep, generally inaccessible erosion gullies. As in previously mapped areas to the east (Cocker, 2003b and 2004a), the Claiborne Group consists generally of massive to finely laminated, white to light tan to brickred, locally kaolinitic, fme to coarse-grained sand and sandstone (Figs. 15- 18). Locally, ground water has stained the sand and sandstones to various shades of yellow and red. Cross-bedding and fine-scale layering may be observed in some of the more indurated, less weathered outcrops. Thin streaks of kaolin, kaolin laminae, and kaolin clasts may also be found. Thickness of the Claiborne Group ranges from 50 to 150 feet.
Because this unit is generally poorly cemented, Claiborne Group sandstones are highly susceptible to rapid erosion. 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 major drainage. Most of the slopes adjacent to the streams have been kept in a natural, forested state to curb that type of erosion. Severe erosion may threaten the integrity of the transportation and utility infrastructure, also.
21

Figure 15. Thin, thinly-bedded clay cross-cutting cross-bedded sand ofthe Claiborne Group (Tcb). Martins Crossroads
Figure 16. Upper contact of the soft Claiborne Group (Tcb) sandstone with the overlying, indurated sandstone of the Altamaha Formation (Ta). Basal conglomerate containing large clasts of iron oxide and iron oxide-cemented sandstone appear to be a few feet above the actual contact. Storm water from the adjacent road has breached the Altamaha Formation and rapidly cut down into the softer Claiborne sandstone. Martins Crossroads quadrangle.
22

Figure 17. Partially silicified sandstone ledge overlying clay bed in the Claiborne Group (Tcb). Martins Crossroads quadrangle.
Figure 18. Large petrified log found in borrow pit developed in the Claiborne Group sandstone (Tcb). Martins Crossroads quadrangle.
23

Eocene to Oligocene Terti11ry Sediments 11nd Residuum (Tsr)
In the current map area, exposures of residuum were found in the southeastern comer of the Cuthbert quadrangle, the southwestern part of the Brooksville quadrangle and mainly in the eastern part of the Martins Crossroads quadrangle. Concentrations of chert rubble accompanied by abundant, predominantly maroon to brown to chocolate brown and less commonly white and orange, plastic or sticky clay is the best indication of this unit's presence (Figs. 19 and 20). Chert and associated brown clays that are the most abundant part of this unit may be derived from intense, subaerial weathering of carbonate sediments.
Chert found in the map area ranges in size from gravel to cobbles and small boulders. Rare chert clasts found associated with Altamaha Formation sediments may be sedimentary clasts eroded from the residuum and incorporated into the Altamaha Formation during deposition of the Altamaha Formation (Cocker, 2004). The paucity of chert clasts in the Altamaha Formation within the current map area suggests that much of this residuum unit was eroded prior to Altamaha deposition and/or not much chert was present in the residuum.
Further to the east, fossils preserved within the chert-bearing residuum have been identified as Early Oligocene (Summerour, 2000) or Late Oligocene (Huddlestun 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 residuum may be derived from the Suwanee Limestone.
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).
Thickness of the residuum unit is quite variable, because it is derived through weathering and erosion of rock units prior to Altamaha sedimentation. Maximum thickness in the current map area is believed to be on the order of 10 to 20 feet.
24

Figure 19. Clay residuum of the Tertiary Sediments and Residuum unit (Tsr) disconformably overlain by the Miocene age Altamaha Formation (Ta). Martins Crossroads quadrangle.
Figure 20. Clay residuum of the Tertiary Sediments and Residuum unit (Tsr) disconformably overlain by the Miocene age Altamaha Formation (Ta). Martins Crossroads quadrangle.
25

Post Upper Cretaceous - pre Miocene K- T breccia/conglomerate (K-Tbx) Several exposures of multilithic breccia or conglomerate or conglomeratic sandstone were found in the
Cuthbert, Georgetown and Brooksville quadrangles. This lithology or lithologies are distinctly different from the adjacent stratigraphic lithologies. In the Georgetown quadrangle, this lithology (Figs. 21 and 22) is on a ridge and is topographically below outcrops of the Miocene Altamaha Formation. A drill hole collared at this occurrence penetrated 44 feet of this rock type before entering a siltstone tentatively identified as belonging to the Upper Cretaceous Providence Formation. In the Brooksville quadrangle, a similar type of lithology (Figs. 23 and 24) is exposed beneath an outcrop of the Altamaha Formation. Topographically below this outcrop are exposures of the Eocene age Claiborne Group sandstone. Exposures in the Cuthbert quadrangle are topographically near the base of the Altamaha Formation and the upper part of the Claiborne Group. Lithologically, exposures in the Cuthbert and Brooksville quadrangles are very similar to each other and distinctly different from the occurrence in the Georgetown quadrangle. The lithology exposed in the Georgetown quadrangle is quite similar to that previously encountered in the Lumpkin quadrangle that lies above the Providence Forrnatiqn and below the Paleocene age Clayton Formation. Based on the differences in lithologies and observed or inferred stratigraphic positions, the occurrence in the Georgetown quadrangle is believed to be older than those in the Cuthbert and Brooksville quadrangles.
These types of lithologies are discontinuous. Those in the Brooksville and Cuthbert quadrangles have been included as part of the Tertiary Sediments and Residuum unit as their exposures are rather limited in extent and not necessarily mappable. Because a significant drill intercept of this lithology was encountered in the Georgetown quadrangle, this occurrence was distinguished as a mappable unit.
The Georgetown exposure, as well as the drill hole, contains large, angular gray clay/shale clasts, up to 2 feet across, along with smaller subrounded to subangular sandstone and kaolinitic sandstone (Figs. 21 and 22). This breccia.conglomerate is dominanted by an apparently sandy matrix.
26

Figure 21. Outcrop of unusual conglomerate (K-Tbx). Angular clast of light gray clay/shale. Georgetown quadrangle.
Figure 22. Subangular to subrounded clasts of kaolinitic sandstone, sandstone and light gray clay (K-Tbx). Georgetown quadrangle.
27

Figure 23. Unusual conglomerate (K-Tbx) exposed beneath lower contact of the Miocene - age Altamaha Formation (Ta). Black pebbles are debris from the basal pebble conglomerate of the Altamaha Formation. Brooksville quadrangle.
Figure 24. Unusual conglomerate (K-Tbx) consisting of abundant rounded to subangular kaolin, gray clay/shale, and sandstone clasts in sandy matrix. Closeup view of Fig. 23. Brooksville quadrangle.
28

The apparently younger breccia/conglomerate is best exposed in the Brooksville quadrangle (Figs. 23 and 24). At this exposure, the exposure is covered by numerous ironstone pebbles derived from weathering of ironstone pebble-rich basal conglomerate inunediately overlying this exposure. The major differences between this exposure and that of the apparently older K-T bx in the Georgetown quadrangle is in the clast population, size of clasts, and the clast to matrix ratio (Fig. 24). Most clasts are less than 2 inches, generally subrounded to rounded, kaolin, sandstone, and light gray clay. This lithology is dominated by the clasts with relatively less amount of apparently sandy matrix.
Presently, the origin of these lithologies, as well as other occurrences observed during previous years of mapping, is unknown. Clast size, poor sorting, and variable angularity of the clasts suggests a relatively high energy environment. The apparent stratigraphic position of these lithologies at the top of the Upper Cretaceous Providence Formation and perhaps during the Eocene (post Claiborne and pre Altamaha), correlates roughly with possible high energy sedimentation related to the Late Cretaceous meteoritic impacts in the Yucatan and Alabama, and with the Eocene age Chesapeake Bay impact.
Albin (1997) and Harris and others (2004) suggest that the origin of georgiaites in eastern Georgia and shocked quartz grains in Eocene sediments may be related to the Chesapeake Bay impact ca. 36.3 and 35.7 Ma. The georgiaites are found as a lag deposit probably derived from the basal conglomerate of the Altarnaha Formation (Albin, 1997). These georgiaites could be derived from the layer found in an eastern Georgia kaolin pit that contained shocked quartz and appears to have been deposited between ca. 37 and 34 Ma. The shocked quartz came from the base of the Twiggs Clay Member of the Dry Branch Formation.
Miocene Altamaha Formation (Ta)
Clastic sedimentary rocks of the Altarnaha Formation are the youngest Tertiary rocks in the map area and are generally found at the higher elevations, particularly on the interfluve areas (Plates 1 - 4). Locally, the Altarnaha Formation is present at lower elevations than its projected lower contact and has been observed in contact with the Tertiary Sediments and Residuum unit, Claiborne Group, Tuscahoma, Nanafalia, Clayton, and Providence Formations (Figs. 6, 16, 19, 25, 26, 27, and 31). Elevation differences in the lower Altamaha contact, as well as cutting progressively older sedimentary units to the north and west, indicate a major disconforrnity prior to (and perhaps during) Altamaha sedimentation. Also, numerous exposures show the Altarnaha Formation downcutting into the older sediments.
Thickness of the Altamaha Formation is also quite variable. Maximum thickness is probably on the order of 20 to 30 feet. The Altamaha Formation may thin to less than 10 feet in many parts of its mapped area. Although the Altamaha Formation is rather thin on the upland surfaces, its indurated sandstones have protected underlying softer sediments from more rapid erosion.
Lithologically, the Altamaha Formation consists of sandstones, argillaceous sandstones, and
29

conglomerates. The dominant lithology observed in the current map area is a massive, brick-red, argillaceous, fme-grained to gritty sandstone. Small, rounded, generally black, ironstone pebbles may be very abundant to rare, but are usually present. Thin or cross-bedding is very rarely observed. Weathering, iron staining and mottling probably mask the presence of more sedimentary structures and textures in the Altamaha Formation. The massive, more or less mottled, argillaceous sandstone is usually found beneath a brick-red sandstone, but are above other brick-red, less argillaceous sandstone.
A basal conglomerate is commonly present that is very useful for recognizing this unit's basal contact. Within the current map area, clast composition of the conglomerate generally consists of iron oxide, iron oxide-cemented sandstone, and ironstone pebbles (Figs. 28 - 32). Clasts of iron oxide were probably derived mainly from residuum of the Clayton Formation. Iron oxide-cemented sandstone clasts were probably derived from one or more underlying sandstone units that locally have iron oxide-cemented sandstone crusts (e.g. Claiborne Group, Clayton(?) and Providence Formations). Rarely, chert or kaolin clasts may be present. Chert clasts were derived from the Tertiary Sediments and Residuum unit, and the kaolin clasts were probably derived mainly from the Nanafalia Formation. Thickness of the conglomerate is generally on the order of 6 inches to several feet.
Altamaha Formation sandstones contain variable amounts of ironstone pebbles that generally range in size from 0.25 to 1.00 inches. Occasionally, ironstone pebbles up to 2 inches are found. Most ironstone pebbles are black and appear to be rounded to subrounded with an apparent polish. Although these pebbles were not examined by petrographic or chemical analyses, visual inspection with a hand lens suggests that these pebbles consist of clastic quartz grains cemented by a mixture of iron oxides, quartz and perhaps hardened clay. These ironstone pebbles are currently clastic in their occurrence. Generally found dispersed in a sandstone or argillaceous sandstone matrix, these ironstone pebbles 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 Altamaha Formation in the current map area ranges from 0 to 50% with the more common abundance probably in the 5 to 10 % range. Weathering of the ironstone pebble-bearing Altamaha Formation concentrates these pebbles as a lag deposit on the present surface (Fig. 32). 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 identified.
The more argillaceous sandstone may be mottled with various shades of white, yellow and red being the most prevalent. Where 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 zone formed by downward mobilization of clay. The amount of clay seems to be variable throughout the current map area. Data from Long and Baldwin (1915) indicate that, despite the enrichment of clays in the subsoils (kandic zone), the rock/soil is an argillaceous sa.-1.dstone based on a greater volume of sands versus silts and clays. Mottling is believed to represent oxidation and remobilization of iron and kaolin by ground water during weathering. Occasionally concentration and
30

precipitation of iron resulted in the formation of hard black masses which are called plinthite. These pebbles have been referred to as plinthite (Summerour, 2000); however, true plinthite is actually a soft, weathering-related segregation of iron oxide to form irregularly shaped masses (Brady and Weil, 1999). Plinthite may be found locally developed as irregular-shaped masses in the lower portions of the kandic weathering zone.
Size analyses and descriptions of soil and subsoil for Grady sandy loam, Greenville sandy loam, Ruston sandy loam, and Tifton sandy loam soils in Terrell County (Long and Baldwin, 1915) suggest that these soils were derived from the Altamaha Formation (Cocker, 2001). As described in the section on soils, these four soil types have the same grain size distribution in the soil and subsoil. Subsoils show a second population of clay-size particles that reflect emichment of clay in the subsurface. The upper soil zone corresponds to the more uniformly colored massive sandstone. The lower argillaceous zone corresponds to the lower mottled argillaceous sandstone. Soils developed on the Altamaha Formation appear to be the best agricultural soils in the map area (Figs. 33 and 34).
In the present quadrangles, the Altamaha Formation disconformably overlies the Claiborne Group, the Tertiary Sediments and Residuum unit, as well as the Tuscahoma, Nanafalia, Clayton and Providence Formations. This disconforrnity can be observed at the outcrop scale where it ranges from 1 to 20 feet (Figs. 25, 26, 27, 28, 30 and 31), from outcrop to outcrop, and at the map scale where relief may range up to about 100 feet between outcrops (Plates 1 - 4). The disconforrnity at the base of the Altamaha Formation marks downcutting in progressively older units to the west and north. Units mapped further to the east (Clinchfield Formation, Ocala Group, and Lisbon Formation) have been removed prior to Altamaha deposition or their lithologies are not adequately distinguishable to be separated and are included in the Tertiary Sediments and Residuum unit.
High angle jointing noted in the area of the Americus atlas (Cocker, 2000b) is generally rarely observed in the current map area. The significance of that is unknown.
Depositional environment of the Altamaha Formation is interpreted as an irregular, prograding fluvial and estuarine system 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 weathering and erosion. As a result, the lower contact of the Altamaha Formation with underlying units is highly irregular. Older units exposed to the weathering and erosion may be irregular in thickness or missing. The contact relations, irregular surface, and variable basal conglomerate clast population are consistent with the anastamosing fluvial channels suggested by Huddlestun.
Detailed mapping of the Altamaha Formation in South Carolina in and near the Savannah River Site (Fallaw and Price, 1992; Nystrom and Willoughby, 1982) contains similar lithologies and has similar geologic relations as those found in the present map area.
31

Figure 25. Channel of the massive, brick-red sandstone of the Altamaha Formation (Ta) cutting into lighter brown and reddish brown sandstone of the Providence Formation (Kp). View is to the east. Georgetown quadrangle.
Figure 26. Channel ofthe massive, brick-red sandstone of the Altamaha Formation (Ta) cutting into lighter brown and reddish brown sandstone of the Nanafalia Formation (Tnt). View is to the north. Cuthbert quadrangle.
32

Figure 27. Two channels of the massive,

sandstone of the Altamaha Fonnation cutting into

lighter brown and reddish brown sandstone of the Nanafalia Fonnation (Tnf). View is to the north. Edge of

channel in the right (east) side of the photo is the left side (west) of the channel shown in Fig. 22. Cuthbert

quadrangle.

Figure 28. Lower contact of Altamaha Formation (Ta) marked by pebble conglomerate with softer sandstone of the Claiborne Group (Tcb). Gully is about 5 feet deep. Brooksville quadrangle.
33

Figure 29. Lower contact of Altamaha Formation (Ta) marked by boulder conglomerate. Clasts are iron oxide- and silica-cemented sandstone probably derived from the underlying Claiborne Group. Brooksville quadrangle.
34

Figure 30. Lower contact of Altamaha Formation (Ta) marked by quartz pebble conglomerate with softer sandstone of the Claiborne Group (Tcb). Gully is about 5 feet deep. Martins Crossroads quadrangle.
35

Figure 31. Lower contact of Altamaha Formation (Ta) marked by quartz and ironstone pebble conglomerate overlying with softer sandstone of the Claiborne Group (Tcb). Martins Crossroads quadrangle .
36

Figure 33. Brick-red soil derived from the argillaceous sandstone of the Altamaha Formation is prime agricultural land. Martins Crossroads quadrangle.
Figure 34. Rich nature of the soil derived from the Altamaha Formation is illustrated by the lush crops. Martins Crossroads quadrangle.
37

Quaternary Tertiary- Quaternary Alluvium (TQal)
Adjacent to the Chattahoochee River are several topographically, generally contiguous, and generally flat areas essentially parallel to the river. The lowermost area, adjacent to the river is defined as being the current flood plain and capped by Quaternary alluvium - essentially alluvial material deposited by the river at or near its more recent elevation. The George F. Russell Reservoir actually represents the position of the river in this study. After a rise of 10 to 30 feet distal to the river, the ground flattens, and is believed to represent a higher, older terrace. No exposures of this higher ground that could be identified as alluvial in nature were observed during the current mapping. Additional terrace remnants may exist higher on the adjacent hillsides.
Quaternary 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, poorly-sorted sand, clayey sand, and clayey silt, with a minor amount of quartz and local chert gravel, and variable amounts of organic matter. The generally larger expanses of swampy areas in the present map area suggest a greater portion of organic matter may be present than in areas further to the east (Summerour, 1999, 2000). Thickness of alluvium is variable and is probably greater in the major creek valleys (Little Ichawaynochaway and Pachitla Creeks and their main tributaries) as well as adjacent to the Chattahoochee River.
Alluvial terraces that were formed during downcutting of the creeks may be present but are not recognizable by their topographic expression on the topographic maps of these quadrangles or in the field mapping. The soft, easily erodable nature of the sediments in the Claiborne Group, Tuscahoma, Nanafalia, Clayton, Ripley, Providence, and Cusseta Formations would tend not to preserve a recognizable terrace.
Alteration of primary sedimentary textures and evidence of previous groundwater movement
Most of the outcrops of Coastal Plain clastic rocks observed during the mapping of the past several years do not display primary sedimentary textures. This is particularly apparent in those rocks that are dominantly red or reddish brown in color (Figs. 6, 25, 26, 27, 30, and 31 ). Alteration of clastic rocks, particularly through groundwater movement and deposition of iron oxides that stain the rocks various shades of red, yellow and brown, appears to obliterate the appearance of primary sedimentary textures.
38

Evidence of past ground water activity is apparent in iron oxide-cemented and iron-stained sediments, as well as mottled sediments. Several episodes of groundwater movement were observed in at least one exposure. Multiple episodes of kaolin and iron oxide mineralization indicate several episodes of groundwater movement along these joints. Cross-cutting joints indicate other periods of groundwater movement.
Correlation of STATEMAP map units with nearby 1:100000 scale maps and the 1:500000 scale Geologic Map of Georgia
On the 1:500,000 scale Geologic Map of Georgia (Georgia Geologic Survey, 1976) the map units which lie within the current map area are the Cusseta (Kc), Ripley (Kr), Providence (Kp), Clayton (Pel), and Nanafalia (Pnf) Formations, the Clayton, Porters Creek and Nanafalia Formations undifferentiated (Pen), Tuscahoma Sand (Ptu), Claiborne undifferentiated (Ec), and Eocene and Oligocene residuum undifferentiated (Eo-s). In the current map area, because of difficulties in distinguishing these units in the field, several of these formations (Clayton and Nanafalia formations plus the Porters Creek Clay) are combined as an undifferentiated unit (Pen). A plot of the Digital Geologic Map of Georgia (Cocker, 1999a) relative to the currently mapped geology of the Brooksville, Cuthbert, Georgetown, and Martins Crossroads quadrangles illustrates a relatively good agreement of the two sets of maps. The principal differences lie in the mapping of Quaternary alluvium in stream valleys, mapping of the Altarnaha Formation (Ta), and Tertiary Sediments and Residuum (Tsr) generally in the stratigraphic position of the Eocene and Oligocene residuum undifferentiated (Eo-s) on the Digital Geologic Map of Georgia (Cocker, 1999a), and the attempt in this project to separately map the lower Tertiary strata. 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).
BIOSTRATIGRAPHY
Outcrops of Tertiary age sediments in the present map area are generally nonfossiliferous. Chert residuum within the Tertiary Sediments and Residuum unit and chert clasts in the Miocene Altamaha Formation are locally fossiliferous in the present map area. In occurrences of this chert further to the east, fossils were identified as Late Eocene, Early Oligocene, and Late Oligocene (Huddleston and others, 1974; Summerour, 2000).
Trace fossils, in the form of Ophiomorpha burrows, are found within sandstone of the Cusseta and Providence and Nanafalia Formations. Burrows are generally lined with kaolin and appear to have kaolin cementing sand within the burrows. These burrows are on the order of 1 to 1.5 inches in diameter and have
39

a thicker kaolin lining. Overall length of individual burrows found in the Providence Formation in the Lumpkin quadrangle may be on the order of several feet and appear to branch (Cocker, 2004). Burrows are generally straight to slightly curved. These burrows may have been built by a clam or crab. This type of trace fossil within shallow or nearshore marine sediments is classified as belonging to the Skolithos ichnofacies of trace fossils (Frey and Pemberton, 1984). These trace fossils are useful as a paleoenvironmental indicators but are not unique to a particular time interval.
The Ripley Formation is normally a relatively highly fossiliferous stratigraphic unit, but fossils were absent in the few exposures observed in the current map area. A summary of the fossils noted by Almand (1961) is included in Cocker (2004).
Several occurrences of petrified wood were found in the Martins Crossroads quadrangle. One occurrence is in a borrow pit developed in Claiborne Group sand and interlayered clay (Fig. 18). The other occurrence was from the Altarnaha Formation near its lower contact (Fig. 35). It could have been derived from older sediments.
Figure 35. Petrified wood fragments from the Altamaha Formation. Martins Crossroads quadrangle.
40

STRUCTURAL GEOLOGY
As observed during the previous years' mapping, scattered occurrences of structural deformation were found in the current map area. Structural deformation observed during this year's mapping includes folding, jointing, slickensides on the jointing and reversal of bedding (Figs. 10, 11, 12, 36, 37, and 38). As with all potential observations of deformation, the following conditions must be present: deformation, bedding or formational contacts that allow the deformation to be observed, and exposure of the deformation. Within the current map area, with the exception of cross-bedding, bedding was generally poorly exposed, developed, or preserved. Larger scale deformation may be present, but could not be well documented because of the lack of subsurface data. Outcrop scale deformation was observed in the Cuthbert quadrangle.
Folding is best displayed by thin-bedded sandstone and clay beds in the Nanafalia Formation (Figs. 10-12 and 37-38). Outcrops of folds observed during the previous years' mapping (Cocker, 2004, 2005) suggest folding has affected bedding in the Providence, Clayton, Nanafalia, and Tuscahorna Formations and the Claiborne Group (Fig. 39). Folding may have affected the Altamaha Formation (Miocene). Folding may have occurred at different episodes during the Tertiary or during one event as early as the late Eocene. Observations during the current mapping did not resolve or clarify timing of these folding episodes. Smaller folds are locally found in the Nanafalia Formation (Fig. 10) and the Claiborne Group (Fig. 39).
As regional dips in this part of the Coastal Plain are to the southeast, bedding dips that are reversed and dip to the north and/or to the west are anomalous. On the outcrop scale, bedding reversals indicate more and possibly larger scale folding is present. In most instances, the entire fold structure or strata on the opposites hinges of the folds are not exposed. A large, asymmetric fold, approximately lJ4 mile wide, is exposed along the old Springvale to Cuthbert road (Fig. 11). Several smaller folds on the order of less than 100 feet wide are visible along the old Springvale to Lumpkin road (Figs. 37 and 38). In a few other places, where bedding was observed in the current map area, sandstone of the Nanafalia Formation (Fig. 12) dips to the west at about 15.
Brittle style deformation is relatively rarely observed in the current map area. A normal fault with a displacement of about 3 to 4 feet down to the northwest involves the contact between the Altamaha and Clayton (?) Formations. Well-developed slickensides are found on a series of joints along the old Springvale to Cuthbert road (Fig. 36). Joint patterns in the current map area and previously mapped quadrangles have not been analyzed at the time of this report. The observed jointing is generally found within the Clayton, Nanafalia and Altamaha Formations. The joints record previous movement of groundwater with formation of kaolin and iron oxide in or adjacent to the joints. Cross-cutting joints record several episodes of jointing and groundwater movement along those joints.
Clark (1965) noted the presence of numerous small faults having displacements of up to 20 feet. U.S. Bureau of Mines drilling indicated vertical dislocations of the Tuscahoma - Nanafalia contact up to 40 feet within a horizontal distance of 100 feet. Unfortunately, documentation of the drill data and evidence for the numerous small faults were not included in Clark (1965) or on his geologic map.
41

. .-' \'"~:\
'.:_ ()
.. .-.

t

-
_,
. ..(,., . ~ ~: ~-.

' '
'
...:;

Figure 36. Slickensides developed along joints in lower Nanafalia Formation (?) clay. Identity of this clay IS uncertain, and it could belong to the Porters Creek Formation or the Clayton Formation. Cuthbert quadrangle.

Figure 37. Right (south) limb of synclinal fold in Nanafalia Formation (Tnt). Cuthbert quadrangle . 42

Figure 38. Left (north) limb of synclinal fold shown in Fig. 37 in Nanafalia Formation (Tnf). Cuthbert quadrangle.
Figure 39. Small scale fold in interbedded clay and sandstone in the Claiborne Group. Brooksville quadrangle. 43

ECONOMIC GEOLOGY
The principal type of ore deposit occurring within the present map area consists of bauxite and high alumina kaolin in the Springvale bauxite district. Identified mines within the Cuthbert quadrangle include the Gamer, Fussell and Yarboro mines. Bauxite was discovered in 1916 and recorded mining lasted until 1922. Production was about 16,000 tons ofbauxite (Clark, 1965). Smith (1929) briefly examined exposures, and in 1943 the U.S. Bureau of Mines conducted a limited shallow drilling program in the area east of the Gamer mine. The U.S. Geological Survey mapped the district and surrounding areas in 1942 and 1943. Results of these investigations are described by Beck (1944) and Clark (1965). Beck provides chemical analyses of intercepts from some ofthe 388 holes. It would appear that only those holes that contained visible bauxite were analyzed. Drill logs were not published, and it is thought by this writer that kaolin and probably kaolinized bauxite, bauxitic kaolin or high alumina kaolin were overlooked and not analyzed. The previous mapping and drilling program (1940's) focused only on bauxite ore bodies and in a relatively small area of the district.
The Andersonville district was viewed in a similar way before it was realized that high alumina materials included various types of kaolin and mixtures of kaolin and bauxite. As a result, significant portions of the Andersonville district have been explored and mined. The Springvale district and the large region between the Andersonville and Eufaula districts have received little published attention with most of the studies being related to WWII mineral resource investigations (Clark, 1965; Zapp and Clark, 1965). The recent STATEMAP mapping and drilling have shown indications of undiscovered bauxite and kaolin resources in this region, as well as stratigraphic and structural complexities (Cocker, 2006b).
During this year's mapping a drill hole (GGS# 4084) was sited to test the area in the vicinity of the Gamer mine (Figs. 40 and 41 ). It penetrated to a depth of 35 feet. Chemical analysis of the core show increasing concentration of Ah03 with increasing depth with the highest Ah03 (55.92 %) at depth. This drill hole was at or near the site of a U.S. Bureau of Mines drill hole that shows no bauxite was found and was not assayed. Results from GGS# 4084 are shown in Table 2, and results of the U.S. Bureau of Mines "discovery hole" number 87 are shown in Table 3. Older assays (Smith, 1929) are included in Table 4.
The U.S. Bureau of Mines employed a power auger drilling method, and results were apparently contaminated by sand. Clark (1965) and Beck (1944) indicated that the alumina could be increased by 5% and silica decreased by 5% to get a more accurate assessment. In assessing the bauxitic ores, the greatest intercept was 49 feet, and the largest deposit was 200 feet long and 50 to 90 feet wide (Clark, 1965). Suggested indicated and inferred reserves of bauxite were on the order of 50,000 to 150,000 long tons of all grades of bauxite (Clark, 1965). That author considered that to be a rough estimate because of the complex nonmarine stratigraphy and faulted nature of the Nanafalia Formation in this district.
This and previous years' mapping and drilling would also suggest that the district's economic geology is complex. Folding is also a consideration and apparently not recognized by the earlier geologists. A plot of bauxite occurrences recorded by Clark (1965) and during this mapping may suggest that the bauxite may occur topographically in the upper and lower parts of the Nanafalia Formation. Exploration of just the upper occurrences
44

may fail to ascertain the total potential of the district. Table 2. Geochemical analysis of GGS# 4084. Spectro ICP data from undisclosed source (2006). Interval Ah03 Fe203 K20 Si02 CaO MgO NaO MnO P20s Ti02 LOI
5 -10' 38.72 1.05 O.oi 44.84 O.ol 0.03 0.02 0.00 0.01 1.81 13.5
10--15' 38.64 1.03 0.03 44.93 0.00 0.04 0.02 0.00 0.01 1.69 13.6 15-20' 39.22 1.01 0.05 44.50 0.00 0.04 0.02 0.00 0.01 1.34 13.8
20-25' 43.20 0.84 0.36 35.71 O.ol 0.07 0.04 0.00 0.01 1.95 17.8 25-30' 50.39 0.76 0.01 22.07 O.ol 0.03 0.02 0.00 O.ol 2.71 24.0 30-35' 55.92 2.24 0.18 12.66 0.58 0.15 0.08 0.00 O.ol 3.15 25.0

Total 100.00 100.00 100.00 100.00 100.00 100.00

Table 3. Chemical analysis of bauxitic clay and bauxite interval from hole 87 (Beck, 1944).

Interval Ah03 Fe203 K20 Si02 CaO MgO NaO MnO P20s Ti02 LOI

10-13' 50.3 1.8 NA 21.3 NA NA NA NA NA 1.8 24.2

13-17' 51.7 1.3

20.3

1.9 24.5

17-20' 51.1 1.4

21.1

2.0 24.2

20-23 ' 52.8 1.2

17.5

2.1

25.9

23-27' 52.4 1.3

17.6

2.3

25.9

27-30' 50.7 1.6

19.1

2.2

25.4

30-43' 54.0 1.3

15.4

2.2

26.6

43-50 ' 52.4 1.1

18.2

2.3

25.3

50-53' 47.1 1.3

28.2

2.1

21.1

53-60' 40.6 1.4

39.7

1.8

16.0

Total

Table 4. Chemical analysis of bauxite from the Springvale district (Smith, 1929).

Sample Ah03 Fe20 3 K20 Si02 CaO MgO NaO MnO P20s Ti02

1

56.23 0.96 0.00 14.42 0.31 0.12 0.00 NA 0.01 2.34

2

39.3 1.41 Trace 43.18 0.00 0.00 0.40 NA 0.10 1.35

3

38.04 1.49 trace 43.13 0.00 trace trace NA trace 1.63

4

52.31 1.41 trace 22.44 0.00 0.00 trace NA 0.00 1.08

5

28.84 2.04 trace 53.06 0.00 0.08 trace NA trace 1.12

6

48.97 1.33 0.06 28.06 0.06 0.00 0.08 NA trace 1.80

Sample 1. Run of the mme bauxite sample from Garner mme.

Sample 2. Bauxitic clay from pit 200 yards west of the main Garner mine

Sample 3. Kaolin from outcrop in southeastern corner of Garner property.

Sample 4. Bauxite from small pits on the West Lee Property, one mile east of Springvale.

Sample 5. Kaolin from Fussell property.

Sample 6. Bauxite from Yarboro mine.

LOI 25.41 14.24 13.30 22.68 13.84 20.80

Total 100.00 100.00 100.00 100.00 100.00 100.00

45

Figure 40. Flooded open pit of the Garner mine that was operated about 1916. Cuthbert quadrangle.
Figure 41. View of the flooded open pit of the Garner mine (Smith, 1929). The view is from the opposite direction of Figure 40.
HYDROGEOLOGY
Aquifers present in the current map area include the Claiborne, Clayton, and Providence aquifers. Depths and aquifer thicknesses are summarized in Table 5. Data were obtained principally from the cross-sections depicted in Plate 5.
46

Sedimentary units that contain the regionally important Upper Floridan aquifer were not found or recognized in the present mapping or in the lithologic logs of previously drilled wells. Ocala Group limestones that are present to the east and southeast of the present study area contain the Upper Floridan aquifer (Cocker, 2003b, Summerour, 2000).
Claiborne Aquifer
The Claiborne aquifer is composed of Claiborne Group sediments. Claiborne Group sediments increase in thickness to the 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 5. Depth and thickness of the Claiborne aquifer shown in Table 5 are derived from map and well data (Plates 1 - 5). Recharge occurs principally through exposures of the Claiborne Group sediments in the interfluve areas or through Quaternary alluvium.
The Claiborne Group sediments are relatively porous and permeable with soils rapidly drained of moisture during drought conditions. Permeability measurements of surface exposures of the Claiborne sediments are reported by Beck (1982). 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). Permeability decreased in the more argillaceous portions of the Claiborne sediments and in outcrops armored by secondary clays.
This aquifer is locally confmed by overlying clay-rich zones in the Altamaha Formation or clay-rich residuum of the Tertiary Sediments and Residuum map unit. The Tuscahoma Formation, where present serves as the underlying aquiclude. Agricultural irrigation and private residentia1 wells are probably the principal users of the Claiborne aquifer. Some of the agricultural wells probably extend into the underlying Clayton aquifer, also.
Clayton Aquifer
The Clayton aquifer is confmed principally to permeable limestones within the Clayton Formation. Within the current map area, the exposed Clayton Formation is represented mainly by a relatively impermeable, clay residuum. Surface recharge into the Clayton Formation is probably minimal because of its surface impermeability, its generally thin to discontinuous surface exposure, and its commonly steeply inclined surface exposure. More significant recharge of the Clayton aquifer may occur in the southeastern most comer of the County Line quadrangle where fresh, porous limestone is exposed north of the Cuthbert quadrangle. Well logs from the Cuthbert city well and wells to the southeast indicate the Clayton Formation is composed of a significant amount oflimestone.
Areas in the eastern part of the Cuthbert quadrangle and the Brooksville and Martins Crossroads quadrangles, which include Cuthbert, utilize this aquifer. Water from a Cuthbert city well contained 39 ppm calclium, 1.4 ppm sodium, 147 ppm bicarbonate, and a spcific conductivity of 254 micromhos (Wait, 1960). Declines in water levels of the Clayton aquifer in the Cuthbert area were primarily attributed to rates of pumping and precipitation (Clark and
47

others, 1984). Water quality of wells at Cuthbert reported by Clark and others (1984) are similar to that reported by Wait (1960). Water quality, transmissivity and potentiometric surface data for the Clayton 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).

Cretaceous Aquifers

In the map area, aquifers below the Clayton aquifer include the Eutaw, Blufftown, Cusseta, and Providence aquifers. Aquifers below the Providence aquifer are not important ground-water sources in the current map area because of greater expenses for well construction, problems of water quality (McFadden and Perriello, 1983), and much of the Eutaw, Blufftown, and Cusseta Formations appear to be relatively impermeable marl. Analyses of water from the base of the Eutaw Formation obtained from the Georgetown city well contains high levels of sodium (123 ppm), bicarbonate (319 ppm), and specific conductivity (497 micromhos) and is unsuitable for irrigation (Wait, 1960). Even the Providence Formation contains water that is marginally suitable for irrigation. Water from the Providence Formation in a well at Ft. Gaines contained 90 ppm sodium, 226 ppm bicarbonate and a specific conductivity of 403 micromhos (Wait, 1960). Measurements of pH in these two wells are also rather high, 8.5 for Georgetown and 8.3 for Ft. Gaines. High sodium values in the Cretaceous aquifers are attributed to leaching of sodium from abundant feldspar in these strata, as well as connate salt water.
A significant portion of the Georgwtown quadrangle consists of exposed Providence Formation. Because much of the Providence Formation appears to be permeable sand, recharge of this aquifer would be significant. 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. Some ground water communication may exist further down dip between the Providence and Clayton aquifers (McFadden and Perriello, 1983).

TABLE 5. Aquifer
Claiborne Clayton Providence

Aquifer characteristics in the study area.

Rock Units Claiborne Group Clayton Formation Providence Formation

Depth 0 to 40 feet 0 to +350 feet 0 to +380 feet

Thickness 0 to +170 feet? 0 to +120 feet? + 250 feet?

GEOLOGIC HAZARDS
Several important geologic hazards that were observed during the present mapping involve soft, commonly unconsolidated sands, soft sandstone, and locally soft clays. Soft sands are found mainly in the Cusseta, Ripley, and Providence formations and in the Claiborne Group. The soft clays belong principally to the Clayton Formations (Cocker, 2006a).
Principal hazards in areas underlain by soft sand include rapid erosion of farmland, roadways, and undercutting and collapse of stream and road banks. Most farmlands are developed on soils overlying the Altamaha Formation.

48

More indurated portions of the Altamaha Fonnation prevent rapid erosion of those soils. Rapid erosion of sandier soils on hillsides Wlderlain by the Claiborne Group and the Providence Fonnation may initiate gullying. Headward erosion may encroach into the overlying Altarnaha Fonnation and the soils developed on top of that unit. Generally, as the slope becomes steeper, erosion and gullying becomes more rapid. Many of the hillsides adjacent to stream valleys have been left to grow as forested land to help prevent erosion. Roadways that TWl down to creek and river valleys and drainage ditches adjacent to the roadways serve to channel TWloff and are particularly susceptible to erosion where they are Wlderlain by the Providence Fonnation or 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 TWloff and resulting erosion. At several places adjacent to paved roads, drainage from the roadways has caused or exacerbated severe erosion (Figs. 42 and 43). Vertical erosion is as much as 15 to 25 feet. Such erosion may cause catastrophic collapse of the adjacent road (Fig. 44). The cliff-like erosional escarpment caused by headward erosion of the Providence Fonnation and Claiborne Group may also be extremely hazardous to hWlters or livestock that may come suddenly upon a 15 to over 30 foot cliff.
Storm runoff from highway culverts (Fig. 43), poor irrigation or logging practices can lead to significant and rapid erosion of the soft sands in areas underlain by the Providence Fonnation and Claiborne Group. Culverts concentrate the flow of storm runoff. Broken, Wlattended irrigation pipes may pump a large flow of water into a stream drainage that is normally in equilibrium. Complete clear-cutting and stripping or burning of fragile groWld cover in sandy terrain significantly inhibits regeneration of the groWld cover that protects the sand from erosion. Erosion and Wldercutting of stream banks may be especially hazardous where structures or infrastructures such as 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 Wldercutting of the stream banks. Areas that have been built up and paved over are more susceptible to increased TWlOff, erosion and stream bank Wldercutting.
Gullies resulting from this erosion tend to collect a variety of trash (Fig. 45). Some of the trash, such as old tires, may be initially placed there in an attempt to prevent further erosion. This practice tends to attract additional trash, as the gullies are perceived to be a convenient place to be rid of old appliances, batteries, containers of agricultural herbicides and pesticides. The Providence Formation and Claiborne Group are both important local and regional aquifers in the southwestern Coastal Plain of Georgia. The various forms of trash may leak chemicals into these aquifers and have a detrimental effect on domestic, agricultural, and public water supplies.
Erosion may have an adverse effect on stream ecology, also. Sedimentation or silting up of streams by sand eroded from the surroWlding terrain reduces the depth and velocity of normal stream flow. Many stream valleys in the current map area are now dominated by broad swamps.
Soft clay of the Clayton and Ripley formations are a geologic hazard especially when the clay is wet. The claybearing Tertiary Sediments and Residuum unit presents a similar hazard. The most frequently encoWltered hazard is on Wlpaved roads where slippery conditions may send a vehicle off course into a ditch, tree or another vehicle. Rutted, dried out clay is also hazardous, as the ruts may also send a vehicle out of control or a vehicle may high center on a rut. Logging trucks commonly use roads in this area, and their heavy loads cause abnormally deep ruts. Local government, e.g. coWlty, road graders are frequently needed to smooth out the ruts. As most roads that cross these formations in the
49

current map area are paved, the Clayton and Ripley Fonnations are a relatively minor hazard. The clay-bearing Tertiary

Sediments and Residuum unit is locally a problem in the Cuthbert, Brooksville and Martins Crossroads quadrangle

because of road construction and more unpaved roads that cross the residuum.

i-r~~

Figure 42. View of erosion gully shown in next picture from bottom of gully. Runoff concentrated by culvert causing rapid erosion and down cutting into soft sandstone of the Claiborne Group. Martins Crossroads quadrangle.
50

Figure 43. Head of erosion gully shown in precedmg photo approachi~g road. Martins Crossroads quadrangle.
Figure 44. Apparent initial road fai lure with fracture arcs focused at head of erosion gully in Claibotne Group
sandstone. Cuthbert quadrangle. 51

Figure 45. Erosion gullies develop as sites for dumping of potentially hazardous materials and contamination of aquifers. Brooksville quadrangle.
SUMMARY
Geologic mapping of the Brooksville, Cuthbert, Georgetown and Martins Crossroads quadrangles (Plates 1 to 4) show the interpreted distribution of Cretaceous, Tertiary and Quaternary sediments. Cross-sections (Plate 5) show the interpreted subsurface geology based on the mapped surface geology. Exposed stratigraphic units in these quadrangles consist of the Upper Cretaceous Cusseta, Ripley and Providence Formations, Lower Paleocene Clayton Formation, and 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. Also, an occurrence of a post Upper Cretaceous Providence Formation- pre Miocene breccia/conglomerate is located. Quaternary alluvium is found in stream valleys and the Chattahoochee River valley. Flat to gently sloping terrain elevated above the Chattahoochee River Quaternary alluvium is interpreted as an older river terrace, perhaps underlain by an older Tertiary to Quaternary age alluvium.
Episodes of exposure, weathering, and erosion followed the deposition of: 1) Upper Cretaceous Providence Formation, 2) Lower Paleocene Clayton Formation, 3) Upper Paleocene Nanafalia Formation, 4) Upper Paleocene Tuscahoma Formation, 5) Middle Eocene Claiborne Group sediments, 6) Upper Eocene Ocala Group sediments; and 7) Oligocene sediments. Several episodes of sea-level advance and retreat are recognized within and between the Blufftown and Cusseta Formations (Rheinhardt and Gibson, 1981 ). An additional episode of exposure, weathering, and erosion during deposition of the Nanafalia Formation recognized in the Andersonville bauxite
52

district (Cocker, 2003a, b), is evidenced by bauxite clasts within the Nanafalia Formation. The complex depositional, weathering, and erosional history of the Tertiary sediments pose a number of mapping and stratigraphic identification difficulties, particularly the placement of the lower contact of the Altamaha Formation between mapped control points.
Exposed contacts between the Altarnaha Formation and older formations indicate a complex erosional surface with significant relief present at the time of Altamaha deposition. Although the extent of post Clayton and preNanafalia erosion is unknown, exposures of the Clayton Formation residuum may only be a few feet thick.
An exposure of the Nanafalia Formation containing abundant bauxite clasts is topographically above reported bauxite occurrences and probably represents some erosion of the bauxite plus kaolin deposits. Reconnaissance drilling and this year's mapping suggest a larger extent to the Springvale district than had been previously examined, and the earlier drilling by the U.S. Bureau of Mines inadequately defmed the mineral potential of this district.
Structural features observed in the map area include synclines and anticlines, bedding tilted opposite to the regional trend, and slickensides on joints particularly within the Springvale District. Common small scale faults are also reported from an earlier report on this district. Structural deformation is noted in the Nanafalia Formation and the Claiborne Group.
Several occurrences of a breccia/conglomerate indicative of a high-energy environment and lithologically inconsistent with adjacent lithologies may be related to impact events. The ages of these sediments are uncertain but are believed to be post Upper Cretaceous Providence Formation and pre Miocene Altamaha Formation.
Recharge of the Claiborne aquifer occurs through the Claiborne Group sediments in the Cuthbert, Brooksville and Martins Crossroads quadrangles, particularly on the interfluve areas underlain by the Claiborne Group sand. Permeability of the Claiborne Group sediments is adversely influenced by an increase in clay content. 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 nonexistent because of the clay residuum.
Recharge of the Clayton aquifer would appear to be nonexistent throughout much of the current map area either because it has been eroded or it is represented only by a residuum of iron oxide and clay. As very little of the Clayton was exposed along the road network, perhaps recharge could occur in the area west of Cuthbert where geologic conditions might be favorable.
Recharge of the Cretaceous Providence aquifer can occur over most of the Georgetown quadrangle. Recharge of the Cusseta aquifer will be more restricted to the northern part of the Georgetown quadrangle.
Exposure of soft, sandy stratigraphic units such as the Claiborne Group and the Providence Formation may result in severe and rapid erosion of these sandy units. Such erosion, which is commonly related to road drainage culverts, can severely threaten the integrity of the road, as well as pose a hazard to road right-of-way maintenance crews. In addition, erosion of the sand leads to sedimentation of the larger streams and deteriation of stream habitats and water quality. Erosion gullies tend to attract illegal dumping of tires, appliances and other refuse, some of which may contain hazardous materials. As the Claiborne is an important aquifer, these materials may enter the aquifer leading to contamination down gradient.
53

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Huddlestun, P. F. and Hetrick, J. H., 1979, The stratigraphy of the Barnwell Group of Georgia: Georgia Geological Society, 14th field trip guidebook: Georgia Geologic Survey Guidebook 18, 89 pp.
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Reinhardt, J., 1982, Lithofacies and depositional cycles in Upper Cretaceous rocks, central Georgia to eastern Alabama; in Arden, D. D., Beck, B. F., and Morrow, E., eds., Proceedings: Second Symposium on the Geology of the Southern Coastal Plain: Georgia Geologic Survey Information Circular 53, p. 89-96.
Reinhardt, J., 1986, Stratigraphy and sedimentology of continental, nearshore, and marine Cretaceous sediments of the eastern Gulf Coastal Plain: Society of Economic Paleontologists and Mineralogists Field Trip #3, AAPG Annual Meeting, Atlanta, Georgia: Georgia Geologic Survey, 99 pp.
Reinhardt, J. and Gibson, T. G., 1981, Upper Cretaceous and lower Tertiary geology of the Chattahoochee River valley, western Georgia and eastern Alabama: Guidebook for the 16th Annual Field Trip, Georgia Geological Society, 88 pp.
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Reinhardt, J., Schindler, J. S., and Gibson, T. G., 1994, Geologic map of the Americus 30' X 60' quadrangle, Georgia and Alabama: United States Geological Survey Miscellaneous Investigations Series Map 1-2174, 1 pl., 1 pamphlet.
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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.
Zapp, A. D. and Clark, L. D., 1965, Bauxite in areas adjacent to and between the Springvale and Andersonville Districts Georgia: United States Geological Survey Bulletin 1199-H, p. H1- H10,1 pl.
58

APPENDIX DRILL HOLE LOGS - 2006
59

Drilled: Location: Total depth: Elevation:
Depth 0-11.0' 11.0 -15.0' 15.0-19.5' 19.5'- 21.0' 21.0-25.5' 25.5 -26.0' Formations 0-11.0' 11.0-25.5' 25.5 -26.0'

Drill Hole: May, 2006
Brooksville Quadrangle 26.0 feet 509 feet (approximate)

GGS#4076

Description

massive, brick-red, fme-grained sandstone.

massive, brown, fme-grained sand.

massive, white, fme-grained sand.

massive, orange, fine-grained sand.

massive, reddish brown, coarse-grained sand; wet.

massive, light brown clay.

Altarnaha Formation Claiborne Group Tuscahoma Formation?

60

Drill Hole: Drilled: Location: Total depth: Elevation: Depth 0-5.0' 5.0-18.5'
Formations 0-5.0' 5.0-18.5'

GGS#4077 May, 2006 Brooksville Quadrangle 18.5 feet 435 feet (approximate)
Description
massive, brick-red, argillaceous, fme-grained sandstone.
massive, grading downward from brick-red to brown to light brown, argillaceous to sandy (11 - 18.5'), fme to medium to coarse-grained sand; coarse-grained from 15 18.5' .
Altamaha Formation
Claiborne Group

61

Drill Hole: Drilled: Location: Total depth: Elevation: Depth 0- 10.5'
10.5 -22.5'
22.5 -47.5' Formations 0 -10.5' 10.5 -47.5'

GGS #4078 May, 2006 Brooksville Quadrangle 47.5 feet 335 feet (approximate)
Description
massive, brick-red to reddish brown, fme-grained, weakly argillaceous sandstone and sand; 8- 9' light tan to white.
massive, light green to light brown in upper 2.5' to rusty brown and brown, very argillaceous, fme-grained, sandstone/sandy clay.
massive, dark gray, micaceous, very argillaceous, fme-grained sandstone/sandy clay.
Claiborne Group
Tuscahoma Formation

62

Drill Hole: Drilled: Location: Total depth: Elevation:
Depth
0 -14.0'
14.0-17.5'
17.5- 20.0'
20.0-26.0'
26.0-26.8'
26.8-32.5'
32.5 -35.0'
Formations
0-32.5'

GGS#4079 May, 2006 Martins Crossroads Quadrangle 32.5 feet 335 feet (approximate) Description massive, reddish brown (upper 5') to light brown, fine-grained sandstone/sand. massive, light brown, coarse-grained sandstone and sand. massive, light brown, fme-grained sand. massive, reddish brown to brown, coarse-grained, sand; water at 25.0'. massive, brown clay. massive brown to light brown, coarse-grained sand. redrill of flowing sand.
Claiborne Group

63

Drill Hole: Drilled: Location: Total depth: Elevation: Depth 0-2.5' 2.5 -12.5'
12.5 -27.5'
Formations 0-12.5' 12.5 -27.5'

GGS#4080 May, 2006 Martins Crossroads Quadrangle 27.5 feet 400 feet (approximate)
Description
no recovery.
massive, brick-red, locally very argillaceous, fme-grained sandstone; abundant ironstone pebbles in lower 6 inches.
massive, red brown to brown with increasing depth, locally light brown, weakly argillaceous to sandy with depth, fme- to medium-grained to coarse-grained with increasing depth, sand; at about 24' about 112" thick rusty clay layer; water bearing 24 to 27.5'.
Altamaha Formation
Claiborne Group

64

Drill Hole: Drilled: Location: Total depth: Elevation: Depth 0-2.5' 2.5- 5.5' 5.5-48.0'
Formations 0-5.5' 5.5-48.0'

GGS#4081 May, 2006 Martins Crossroads Quadrangle 48.0 feet 376 feet (approximate)
Description
no recovery.
massive, brick-red, argillaceous, fme-grained sandstone.
massive, light brown, reddish brown, purple to orange, fme- to coarse-grained sand; generally fine-grained 5.5 - 26', medium-grained 26- 36', coarse-grained 36- 45.5', fme-grained 45.5- 48'; wet 26' to bottom ofhole and very wet at 38'.
Altarnaha Formation
Claiborne Group

65

Drill Hole: Drilled: Location: Total depth: Elevation: Depth 0-2.5' 2.5- 8.0' 8.0-10.0' 10.0-14.0' 14.0-15.0' 15.0-15.5' 15.5- 35.5'
Formations 0-8.0' 8.0 -35.5'

GGS#4082 June, 2006 Martins Crossroads Quadrangle 35.5feet 320 feet (approximate)
Description
no recovery .
massive, brick-red, fme-grained sandstone.
massive, light-brown to white, fme-grained sand.
massive, mottled, argillaceous, fme- to medium-grained sandstone.
massive, reddish brown, ftne-grained sandstone.
laminated, reddish brown silt.
massive, white to red to brown, weakly micaceous, fme- to medium- to coarse-grained sand; 15.5 - 25.5' fme-grained, 25.5 - 30.5' medium-grained, 30.5 - 35.5' coarsegrained; wet in lower 5 feet; also a few, thin, weakly iron oxide cemented layers 15.5 .,... 20'.
Altamaha Formation
Claiborne Group

66

Drill Hole: Drilled: Location: Total depth: Elevation:
Depth 0 - 2 5 .5 '
25.5 -28.0' 28.0-43.0' 43.0- 50.5'
Formations 0-28.0' 28.0- 50.5'

GGS #4083 June, 2006 Martins Crossroads Quadrangle 50.5 feet 350 feet (approximate)
Description
massive, very strongly mottled, strongly argillized, fme-grained sandstone; brown, red, white, black and green. massive, brown, hard, sandy clay; minor iron oxide cement at 28'.
massive, light brown, fme-grained sand. massive, brown, fme- medium grained, wet sand; very wet from 45.5- 50.5 '.
Altamaha Formation
Claiborne Group

67

Drill Hole: Drilled: Location: Total depth: Elevation:
Depth
0-2.5'
2.5- 35.0'

GGS#4084 June, 2006 Cuthbert Quadrangle 35.0 feet 380 feet (approximate)
Description
no recovery
massive, brownish white to light gray, massive kaolin; weak iron oxide stain at 2.5- 5'; local iron oxide stain scattered down hole

Formations 0-35.0'

Nanafalia Formation

68

Drill Hole: Drilled: Location: Total depth: Elevation:
Depth 0-2.5' 2.5 -43.5'
43.5 -50.0' Formations 0-50.0'

GGS#4085 June, 2006 Cuthbert Quadrangle 50.0 feet 410 feet (approximate)
Description
no recovery
apparently thinly bedded, ligh gray to light brown to rusty brown clay; bedding about 70 deg. to core axis; minor iron oxide cement 12.5- 13'; iron oxide on fractures from 25.530'
massive, brown, highly glauconitic, argillaceous, fine-grained sandstone
Nanafalia Formation?

69

Drill Hole: Drilled: Location: Total depth: Elevation: Depth 0-2.5' 2.5- 25.5'
25.5- 50.5'
Formations 0- 50.5'

GGS#4086 June, 2006 Cuthbert Quadrangle 50.5 feet 40 1 feet (approximate)
Description
no recovery
at about 4 feet apparent bedding, about 70-75 deg. to core axis; otherwise massive, light orange brown, weakly kaolinitic, fme - to medium-grained sand; several kaolinitic beds @4-5.5'.
massive, white to light tan, weakly sandy kaolin; quartz </= 10% near top grading to </= 1% in lower half; 4" thick sand at 28' with contacts about 45 and 30 deg. to core axis; sand is si..tttilar to base of upper sand.
Nanafalia Fonnation

70

Drill Hole: Drilled: Location: Total depth: Elevation: Depth 0-2.5' 2.5- 9.5'
9.5- 10.5' 10.5 -16.0'
16.0- 32.0'
32.0-50.5'

GGS#4087 June,2006 Cuthbert Quadrangle 50.5 feet 390 feet (approximate)
Description
no recovery
massive, reddish brown, micaceous, kaolinitic, fme- to medium-grained sandstone; black iron oxide crust at 4 to 4.5 '.
massive to laminated, rusty brown, strongly argillaceous, fme-grained sandstone.
massive, reddish brown micaceous, kaolinitic, fme- to medium-grained sandstone; coarser in lower 1.5'.
massive to locally faintly bedded, light gray to black kaolin; light gray in upper 2' then grading to black and back to light gray at 23'; apparent bedding at 21' @ about 70 deg. to core axis; iron oxide speckling at 28- 30.5'; lower contact@ 30 deg to core axis.
massive, white, micaceous, kaolinitic, fme-grained sandstone and sand.

Formations 0- 50.5'

Nanafalia Formation

71

Drill Hole: Drilled: Location: Total depth: Elevation: Depth 0-6.0' 6.0-56.0'
Formations 0-6.0' 6.0-56.0'

GGS#4088 July, 2006 Brooksville Quadrangle 56.0 feet 485 feet (approximate)
Description
massive, brown, argillaceous, fme-grained sandstone.
massive, light brown to white, locally gray, very fme-grained to coarse-grained sand; very fme-grained 6- 31', coarse-grained 31- 33', 33- 38' fme-grained, 38- 38.5' coarse-grained, 1" thick, brown clay and iron oxide cemented sandstone at 38.5' dipping 80 to 85 deg. to core axis, very fine-grained 38.5- 40', 4" coarse-grained at 40', fmegrained 40 - 41 ', 41 - 46 very coarse-grained to coarse-grained, fme- to medium- grained 46- 56', at 48' wet sand to base.
Altamaha Formation
Claiborne Group

72

Drill Hole: Drilled: Location: Total depth: Elevation: Depth 0-2.5' 2.5 -45.0'
45.0- 50.5' Formations 0-45.0' 45.0- 50.5'

GGS#4089 July, 2006 Georgetown Quadrangle 50.5 feet 510 feet (approximate)
Description
poor recovery
massive, mainly brick-red, argillaceous, fme-grained sandstone; locally light brown from 22- 22.5'; contains abundant clasts; white kaolin clasts mostly smeared by drilling, <J= 4"; also light gray to brown clay, 3" thick; medium gray clay clasat at 4.5'; minor slickensides; also a few subrounded sandstone clasts.
massive, reddish brown, micaceous silt and clayey silt.
Tertiary/Cretaceous? breccia/conglomerate?
Providence Formation?

73

Drill Hole: Drilled: Location: Total depth: Elevation: Depth 0-7.5' 7.5 -15.0' 15.0- 21.0'
21.0-25.0' 25.0-30.0' 30.0- 33.5' 33.5- 39.5' 39.5 -43.0' Formations 0-7.5' 15.0-43.0'

GGS#4090 July, 2006 Georgetown Quadrangle 43.0 feet 510 feet (approximate) Description massive, brick-red to weakly mottled (5 -7.5'), argillaceous, fme-grained sandstone. no core massive, white and purple in top 2.5' to reddish brown and tan, weakly micaceous clay grading to siltstone. massive, reddish brown to red, micaceous silt and clay. massive brown clay and light brown, fossiliferous limestone fragments. massive, brown to reddish brown, wet, fme-grained sandstone and sand. massive to locally laminated, brown and black, clay, micaceous clay and argillaceous silt. massive, green to rusty brown, micaceous clay; a few inches of wet sand near base.
Altarnaha Formation ':;layton Formation

74

T:Md-., D ST ATES DEPARTME:N!r OF THE INT ERIOR
S URVEY

Georgia Geologic Survey Open-File Report 06-1

GEORGETOWN QUADRAN G~E
GEORGIA- ALAB AMA I 5 MIN UTE SERIES ITOPOORAPHIC)

Plate 1

Location Map cf U1e ~eurgeluw n 75 rru r.ule quadrangle

ll

p ~ l>tis lh e d by the Geological Suf'Jey
CQntrQI by USG:!S;,,:;:::~~~,,~
Tc-pOj;raptJy by p'
photQgraphs taken

Polyconrc pro1eo:::t ron TO,OQO-!oot grn;fs based on <ieorgl ~

coortlmote system,

Al abama c.M rd on<lte

system east zone

1Transve rse

Merca tor gml'

111 t. lua 192 ? North

Am l'r tr;<~a Datum

pred l(; ted North A m~nr.:.~n

Datum 1983 m<:Nt: 7 meter<; w~ s l as slww r

11'- meter.> sJuth and

UTM G"ID liND 1981 MAGN ETIC ~lO P. { DEC clri An DN I.T ~<' Nn ~ r>t S H ~ ET
R eW !S~II~ :>nM 11 In ruc;::f':! ;;r,<j o\'OOCl ~r.d ' 0~1pf le<J IN)I aennl phatograph> t~ke'1 J979 .;~-n<J otOOt liOt rcN;
Tr11', mfurma+11m nol lle!d c.n ~>c~6d N1ap 001te.d 1981

CON TO u r~ INTER VAL lO rt:ET NA"~"iONAl Sf:OO..I IG VEIHICA!. DATUM o~ l>I ~ Y
[ H S MA P COV! PLIL-' Wii\-1 NATIO NAL "'AP AC CU RA-.1' S T A N U ~ R D ~ FQR SA L!:. !3 Y lJ S GEOLOC,IGA . SU RVEY RE.STO N 'ldRG NIA 2 20 92 A F\JL D E.~ DtSCRI\31NG TOPOGRAPHI C '<lA PS AN D SYMBOlS IS AVAILABLE ON REQUESr

FW

ROAD ClASSIFIC AT iON

Pn mal)' hrghwa y all wea the r,
hard surtace
Seoond;;: ry rughway, aDweather ha1 d su fac:e ~ ~-""- -~~-

Lrght duty road aH wt!ath P.r , rmproved surfacP. - ~~~
Ummproved roa d rarr or dry wea tner ~ __ ~- .., ~ ,. -~~---

iJ u S Route

( ) ::ilate r~oute

GEORGETOWN, GA -ALA
t\1.3 :5 2 5- NB500/7 5
lCl67 PHOl OR E V I~ECl l 981 DMA 3947 I NE'-SERJE S V8 4:>

Explanation

Map Units

0 D
u
Q
-

Wulet Qa l Quatcrna1y Al h1 v1um - poorly sorted ::all Stlnd awl gravel TQal Tert1ary - Quaternary ? Alluvmm lerrace defK!Sils
- poorly snrterl s1lt, sand cmd gravel Ta Mwrenc Altama ha Formulwn - musSJve ar~Jllilceous st~ndsbne Kfbx'i M1lL! th1c breccJn - conglomeratiC sanddcnc - ct6CJnrcrlat ll lei I.::Jlif.J Pt~leo:x:em; Clct) to[] rormalion - maSSIVe blOC ]asttc IJmestone or
re~rrlllllfil of clay non oxrde .:md mmor chert Kp li ~per Cretaceous Prondence Formallon - massne to cnss-bedded.
mtcaeou::; kaolim lJc s~ ndstone

Kr Upper Cretaceous Rtpey Formatmn - ma~Jvc llllcuceous,
glaucomttc, [me-gramOO sa nd and silly day Kc llpp~r Cretaceous Cu~eL1 Fmmalmn - massm +o cross -bedded,
io".all ; kaolm1 ~1C, rnedt tl:ll Lo coarse-gramed sal'dsloue

Lme of cro~s ~ect1 on Wdl (lf CO!e hult localJ on Contact (located approxtmalely)

eo logic Map of the Georgetown Quadrangle, Georgia

Geology by Mark D Coc ke r D1giuzed and digitally compi1ed by Mark D. Cocker Map proJechon, Albers Conic Equal Area NAD27 August, 2006 Supported by the US . Geological Sur vey, Natwnal Cooperative Geologic
Mapping Program , uoder a ssistance Award Agreement #OSHQAG0016

i

UNITED STATES DEPARTMENT OF T H E INTERIOR
GEOLOGICAL SURVEY
... '\
\
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STATE OF GEORGI A DEPARTMENT OP MINES, MINING, AND GEOLOGY
D1V1S ION OF CONSERVATION
' '

Tcb

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Georgia Geologic Mapping Program Open-File Report 06-1
Plate 3

BROOKSVILLE QUADRANGLE
GEORGIA - RANDOLPH CO.
?.5 MINUTE SEFIJfiS (TOPOGRAPHIC)

Tob

...--:----:.'

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Location Map of the Brooksville 7.5 Minute quadrangle

GGS,# 3387
0"-

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"

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GGS #3391 '.

./ -,,

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~~~~"~~Jr~~~-Q~L~L-~~~~(E_;l~r~:-;sJ[~~~~~~~?.~~;;?"A""__jl,~~~~J~]~~l~~~~~~:.'L_"',_--~ ,I\.,5a;..~~~ ~ Map~ed . edited,end published b~ thfl Ge(Jiogicaf Survey
i-(} ,._'<-

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uzo

SC.IILE 1:24 DGO

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--+---;n-' 2J

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37

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5'

f-~ ,,
~r}"ti,.1

Contrcl by USGS ,; nd USC&GS
"" or-,_,r, r~p~~ :;.y pr,orogr.;:mmetriC rTI~tiJ"i:!s fwm aP.." !.:t! ph&togt<'p/l s t;~ !o.en 1972 . l-le!cJ r. hed.cd 1972
ProiccliCn "' ''d IJ,OOO-f(lo t grid ! ids: Gt!or;: 8 (;::.ordinat e

'' tr~ M'..'.

'- ,2:..,J-,_t_Ct .===J-G-[\s1

. - -. . . . ,';

(I

~ ~-~ ~=

1 ~~~M [ ll H -:=.........-------l

R0 .>'\0 CLASSJri CfiSI ON

Prim<s ry highW<l)', hard ~urace

Ligl"ot- dlw l~ 10<1d . harrl or im!J:cw-ad $ll rfa~e

.Sceonda(y hiB hway,

Sy q ~m, "'1<051 l one (ir<J il51i l;rs.e M ~rca to r )
1000- m~tl.' r lJniv.;rs ~l T r~ r1~:erse Me!c a tllr ~-i U t ds, .z: rre ~6. ~ ho.w1 ,,.. bl u ~. 1927 Ncrth Ame n:an d~tu r !l

..-',;;ccr'! ::.cr._

.

' ~ ~~
'

C Ot;!" ~)l f< lNIEP. 'o/!d. 10 FE:.ET
f:".7 l' l"' !S l~ f A~J ~;;; L f: Vf:l_

hatd surface.. _______ _,_,_~ U.S . Fbu.te

.. - - -- - ~- ~-StillE' i<oute

Fi ""' red :'ashed lin= i <JUc ~ u~ :.;~ lecl~!d tenc<: a nd f a!C li nes v;hertP. I'rle ra!!y vis ttll e Dll ae ri~l pluoltIO r<~p~~- T\', .~ IMIMm;;ti(P ~ un-;\; e-ckE;d

1..> " ,~ Gf'W JooltO !\."~ loi~G~HIC ~<liHil !J[C'lHHill)H M C !MTE~ G F" SHf.ET

THI S MAP C0 r-1 ?U E S WfiH NATIOt-iA L MAP ...C CIJ RM; y S'r.... NOA.f! ll S
FOR' SA LE BY 'J . S. (;EO LOGICAL SU RVEY, RESTON, VIRG INIA 22092
/1. HllDEH llES (;.fl iDlN:> l"Of'OGHI\PH I(; 1.1~ f'S .~Nl) SYI!>I[)()LS IS AVAKfLHLE or; ll~:~J UEST

BROOKSVILLE, GA.
J\13-.J 45 - 'N84"JI' _51 7.5
l97l

Explanation
Map Units
c=J Water c=J Qal - Quarternary Alluvium- poorly so1ted silt, sand and gravel c=J Ta- Miocene Altamaha Formation -massive argillaceous sandstone c=J Tsr- Tertiary Sediments and Residuum - massive waxy clay and locally abundant chert c=J Tcb- Middle Eocene Clairbome Group -massive to cross-bedded, fine sand and sandstone c=J Ttu- Upper Paleocene Tuscahoma Formation- thin bedded clay, silt, and sand
~ Cross Section
V \ l Contact (located approximately)
~ Well or core hole location

Geologic Map of the Brooksville Quadrangle, Georgia

GeoloJ:,')' by Mark D. Cocker D igilized and digitally compiled by Mark D. Cocker Map projection, Albers Conic Equal Area NAD27 August. 2006 Supponed by t he U.S. Geological Survey, National Cooperative Geologic Mapping Program, under assistance Award Agreement #OS HQAGOOlG

UNITED ST DEPARTMENT OF
GEOLOGJCAL

STATE OP GEORGIA
DEPARTMENT OF MINES, MINING, AND GEOLOGY DIVISION OF CONSERAT!ON

Georgia Geologic Survey Open -F ile Report 06 -1
Plate 4
MARTINS CROSSROADS QUADRANGLE
OEDRG!A 7.5 MINUT E SERIES (TOPOGRAPHIC)

Localion Map cf the Martms Crossroads 7.5 mmu tc qu<ldmngle

Mapped , edited, and publ ish ed by the p eological Survey

Ca J1 tm l b y USGS Dnd USC&GS

To pngr ~phy I.Jy photo~rammetr lc melhods

ohc tog rapns hkerl 1972. Freid''"''" '"

ProJ ~ ctio'l and 10,000-toot grd to't'k:;, j:;,o/' '' coordrn~ ifl

sys tem, WEt;t zonfl (tr>~tr<:Vc r~ c ":'~,;~;,! ,,.

10f 0-ntter UrH...-er.;a 1 Transverse

i tr c l,.~ .

da~h"d ~ o cl M 1e;, ~11owr~ lr, blue. 1927 North 4 c,,!,io.odalum

Fmf: cd

tmes hdk:ate selecl<:ed

<tnd f1eld Hies Yd1ere

gen ~ r<Ll 'I 'll!ii bl.a or, a{lroM pC.oior,mphs

mtormation l$ U'Khcded

UfM G 'll~ II~!,) 1~7) ~A.G.t.:.FTIC I'IQ ilT >l GtCUIUT oOtl ).1 C iONfE~ Of ~HE:H

CONTOUR INT[RVAL 10 rEF.i
NII.TIONAt.. QEODE.TIC Y[RIICJ'.L DATU~ OF 1~ 29
fHIS MAP COrr.IPLIE S WITI-1 NA.110NI\L MAP ACGURA C'r' S'r)I.NOARDS FOR SII LE BY {J. S. GEOLOGICAl SURvt;i", RE.STON, 1/I~GINI/\ 2?092 A FOUlER DESCRIBING TOPOGRAP HIC MAPS AND SV MBOLS IS Alfi. ILAfKE ON REQUEST

' I o.,,
\l (iEOrx; A\

)

\

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i

''-----,1j

QlJI\fJflM'~,_f L()OT!Cil.l

Primary h1ghway,

light duty road, ha rd or

hard suri:o..<e ----- -- - - - improved surfar::e... ~-==-----=

Sacond~ry higli ....ay,

hard surfat:e.

() lnter!ifC~te Rvute

r
L


-'

U.S

Rou tt<

( ) ~tate Fbn~~

MARTINS CROSSROADS, GA.
N3 137.5-W8437.5/7 5
1973
AMS 40 47 II NW -SERIE:S \'845

Explanation

Map Units

CJ Water

c:::::J Qal Quaternary .~lluvium - poorly sorted sit~ Silnd and grnvcl

0

'fa Mi~ene Altarnaha Formation - mas;,tvc argillaceous sandstone

E:J Tsr Terbirf Sedimnls and Residuum - masstve waxy clay and locally abundant chert

Mtd\\le Eo~e11~ Ck.iborne Group - ma&:!Ye lo cross-bedded Lne sand and saudslune

Tlu Late Paleocene 'fuscahoma ~ormatJOn - thm bedded, clay, sill and sand

Well or co~e hole location Contact (lo'alrd apprcximatelyl

G ologic Map of the Martins Crossroads Quadrangle, Georgia
Geology by Mark D. Cocker Digitized and digitally compi1ed by Mark D. Cocker Map projection, Albers Conic Equal Area NAD27 August, 2006 Supported by the U .S. Geological Survey, Na1ional Cooperative Geologic
Mapping Program, under assis1ance Award Agreement HOSHQAG0016