locally cherty clay or marl; and occasional beds of light-gray, sandy, coarsely glauconitic limestone. The 

 top of the sand section, which generally is also the top of the Tallahatta Formation in updip areas, usually 

 contains abundant molluscan shells, giving a coquina-like appearance. Examples of this type of lithology 

 are found in wells situated in southwest Georgia, particularly in Terrell, Lee, and Dougherty Counties. 

 At the base of the Tallahatta in updip areas, prominent chert beds are often found, a feature that is so 

 particularly characteristic of this formation is southwest Georgia that the bed was formerly called "buhr- 

 stone." Interfingering with these elastics, the downdip Tallahatta consists of light to dark-brown, saccha- 

 roidal, coarsely glauconitic, locally fossiliferous limestone that is interbedded with occasional beds of 

 fine to coarse-grained, granular limestone. The downdip limestone facies of the Tallahatta Formation 

 is similar to that of the overlying Lisbon but is much more dolomitized and considerably more glauconitic. 

 The middle Eocene gradually increases in thickness from a few feet in its outcrop area to over 1,300 

 feet in southeastern Georgia (see fig. 9). An area of greatest thickness, or depocenter may occur in south- 

 west Georgia. 



Some of the published articles in which many of the middle Eocene Foraminifera are described and illus- 

 trated include those by Howe (1939), Cushman and Todd (1945), Cushman and Herrick (1945), Cole (1929), 

 Applin and Jordan (1945), and Bandy (1949). A few of the more commonly occurring guide Foraminifera 

 of the Lisbon Formation in Georgia include: Buliminella robertsi (Howe and Ellis), Discorbis inornatus 

 Cole, Asterigerina lisbonensis Cushman and Todd, Cibicides westi Howe, Cibicides pseudoungerianus 

 (Cushman) var. lisbonensis Bandy, and Lepidocyclina antillea Cushman. Some of the fossils indicative of 

 the Tallahatta Formation include Valvulineria danvillensis (Howe and Wallace) var. gvroidinoides Bandy, 

 Cibicides blanpiedi Toulmin, Cibicides pippeni Cushman and Garrett var. stavensis Bandy, Cibicides 

 tallahattensis Bandy, and Asterocyclina monticellensis Cole and Ponton. The faunal lists in table 6, though 

 by no means exhaustive, reflect the Foraminifera found in the two types of facies-environment that existed 

 in early and late middle Eocene time in Georgia. 



28 



