THE EOCENE PERIOD. 199 



Nanjemoy formations), the Lower Eocene only is represented in the 

 exposed beds referred to this period. In Virginia, the Middle Eocene 

 is also present, and in the Carolinas, the system is still more complete 

 (Buhrstone, Santee, Cooper, the last sometimes classed as Oligocene), 

 though the oldest Eocene beds are thought to be wanting. In Florida, 

 the Upper Eocene only is exposed. The interpretation of these varia- 

 tions will be readily made. 



The Gulf border. — The Eocene system is more fully represented 

 in the Gulf region than along the Atlantic coast, and the Lower, Middle, 

 and Upper divisions are more clearly defined. Their aggregate thick- 

 ness is not less than 1700 feet (maximum), of which something like half 

 belongs to the Lower Eocene, and more than half of the remainder 

 to the Middle. 



The section in Alabama, which may be taken as fairly typical of 

 the Gulf Eocene, is as follows: 1 



Upper Eocene White limestone (Jackson and Vicksburg, the latter 



sometimes classed as Oligocene) 350 feet. 



Middle Eocene. . . .The Claiborne series: 



Claiborne formation, mainly clays and sands, 



calcareous and glauconitic 140 ' ' 



Buhrstone formation, mainly sand with some 



glauconite 300 ' ' 



Lower Eocene The Lignitic formation, mainly sands and lignite 



(Chickasaw) 900 " ± 



The Clayton (or Midway) formation, mainly 



limestone 10-200 " 



It is on the basis of the Eocene of this region that the following 

 classification has been suggested for the Eocene of the east: 2 



(a) Jacksonian Upper. 



(b) Claibornian Middle. 



fa giickasawan 1 Low 



(d) Midwayan J 



The relations of the Eocene strata to the Cretaceous 3 are much 

 the same in the eastern Gulf States as on the Atlantic coast. They 

 outcrop in a belt just south of that where the Cretaceous beds appear, 



1 Smith, Geol. Survey of Alabama, 1894. 



2 Dail, 18th Ann. Rept. U. S. Geol. Surv., Pt. II. This classification places the 

 Vicksburg in the Oligocene, instead of associating it with the Jacksonian. There 

 appears to be no physical reason for this separation. 



3 Smith, Geol: Surv. of Alabama 1894. 



