Cretaceous System 



UPPER CRETACEOUS SERIES 



Posi-Tuscaloosa deposits . — Cretaceous sediments of post-Tuscaloosa age have been identified in 

 90 wells in 33 counties of the Georgia Coastal Plain. Post-Tuscaloosa deposits have been found throughout 

 the Georgia Coastal Plain except in the northeastern part where the lithology of the post-Tuscaloosa is iden- 

 tical with that of the underlying Tuscaloosa Formation. As pointed out by Eargle (1955, p. 5-6) the "Tus- 

 caloosa" as found in this northeastern part has been identified on the basis of lithology rather than by 

 stratigraphy. However, because foraminiferal evidence is nonexistent to support this opinion, the Tus- 

 caloosa-type sediments in the northeastern part have all been logged as Tuscaloosa Formation (Herrick, 

 1961). In preparing maps however the data in the northeast were considered to indicate only the top of the 

 post-Tuscaloosa (see fig. 14). On the map showing thickness and distribution of the post-Tuscaloosa de- 

 posits (fig. 15) as well as the maps showing the Tuscaloosa top (fig. 16), and its thickness distribution 

 (fig. 17), the northeastern part was left uncontoured because of this uncertainty. 



From study of outcrops in western Georgia, the post-Tuscaloosa has been divided from top downward 

 into Providence Sand, Ripley Formation, Cusseta Sand, Blufftown Formation, and Eutaw Formation, all 

 of which are extensions of the same formations as found in eastern Alabama (Eargle, 1955). These forma- 

 tions when traced downdip in the subsurface gradually merge into three units that are faunally distinctive 

 and which for lack of formational names are considered to be equivalents of beds of Navarro, Taylor, 

 and Austin age. The updip formations correlate with the downdip beds as shown in Table 9. It has been 



Table 9. — Correlation of surface and subsurface units 



of post-Tuscaloosa Cretaceous age 



41 



