Lower Eocene rocks.— in the Coastal Plain of Georgia, strata of early Eocene age have been iden- 

 tified in approximately 50 wells, the majority of which, however, are in southwest Georgia. The updip, 

 clastic facies of this unit is correlated with the Wilcox Group of Alabama, whereas its downdip limestone 

 equivalent is correlated with the Oldsmar Limestone of Florida. In southwestern Georgia, where the lower 

 Eocene deposits are of the clastic type, this unit can be broken down into the Tuscahoma and the under- 

 lying Nanafalia Formations. Moreover , in some wells, particularly in Sumter and Dougherty Counties, 

 the top of the lower Eocene is often represented by abundantly glauconitic, silty, abundantly micaceous, 

 somewhat fossiliferous marl which doubtless represents erosional remnants of the Bashi Marl Member 

 of the Hatchetigbee Formation. Elsewhere intheCoastal Plain of Georgia these beds have not been observed. 

 The subsurface areal extent of the lower Eocene in Georgia is considerably less than the previously 

 discussed stratigraphic units (see fig. 10). This is due, in part, to overlap by geologically younger forma- 

 tions and in part to offlap causing the sea to have been restricted in Georgia during early Eocene time. The 

 lower Eocene deposits crop out along the Chattahoochee River as far north as the center of the west edge of 

 Clay County. From here the northern limit of this unit trends northeastward across the Coastal Plain 

 through the centers of Webster and Schley Counties to the south-central part of Macon County where these 

 sediments are overlapped by geologically younger deposits. From the point of overlap in eastern Macon 

 County, the updip limit of the lower Eocene is approximated in wells as a line trending eastward across the 

 Coastal Plain through Treutlen County, thence east to southeastern Screven County. The updip, clastic 

 facies of the lower Eocene consists of interbedded, dark-gray to dark-brownish-gray to chocolate-brown, 

 blocky, silty, carbonaceous, micaceous, pyritiferous, glauconitic, fossiliferous clay or marl; fine to coarse, 

 glauconitic, lignitic, pyritiferous sand; and a few beds of white to light-gray, sandy, coarsely glauconitic, 

 micaceous, shelly, coquina-like limestone. As noted in wells the elastics gradually grade into limestones 

 far down the dip, with the transition zone extending from southwestern Echols County northeasterly 

 through Clinch, Brantley, Wayne, Glynn, and Mcintosh Counties to northeastern Chatham County. The 

 limestone facies of the lower Eocene in Georgia consists of cream, much calcitized, somewhat granular, 

 coarsely glauconitic, locally cherty and dolomitized, somewhat fossiliferous limestone. Lithologically 

 the limestone is similar to the overlying limestone of the Tallahatta Formation. A shelly, somewhat 

 indurated, coquina-like sand persists in the basal part of the lower Eocene unit as far downdip as Echols 

 County and possibly as far as Clinch and Camden Counties. This shell-bearing sand is correlated with the 

 basal part of the Nanafalia Formation of Alabama. The lower Eocene deposits gradually increase in thickness 

 from a few feet in the outcrop area to over 400 feet in Clinch, Charlton, Glynn, and Camden Counties (see 

 fig. 11). Owing to lack of subsurface control, the presence (or absence) of possible depocenters belonging 

 to this stratigraphic unit is difficult to determine. However, it is possible that such areas may occur off 

 the coasts of western Florida and northeastern Georgia, the latter area possibly centering off the coast 

 of southeastern Chatham and eastern Bryan Counties. 



Literature dealing with the Foraminifera of the lower Eocene is not as voluminous as that for the pre- 

 ceding units. Some of the paleontologic articles deserving mention here are those by Cushman (1944), 

 Cushman and Ponton (1932), Toulmin (1941), Loeblich and Tappan (1957), and McLean (1953). A few of 

 the guide fossils for the lower Eocene include Valvulineria wilcoxensis Cushman and Ponton, Valvulineria 

 scrobiculata (Schwager), Eponides dorfi Toulmin, and Globorotalia wilcoxensis Cushman and Ponton. 

 Helicostegina gyralis Barker and Grimsdale has been observed in one well in Clinch County. The faunal 

 list in table 7 summarizes the more important smaller Foraminifera occurring in beds of early Eocene 

 age in Georgia. 



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