282 



HISTORICAL GEOLOGY 



very large percentage in the latest series. Later the Oligocene was 

 added by combining some of the uppermost Eocene with some of 

 the lowermost Miocene, though in North America the term Oligo- 

 cene has been but little used till very recently, and even now such 

 strata are not always separately differentiated. 



Following are the principal subdivisions of the Tertiary as now 

 recognized in various parts of the United States: 





TERTIARY SYSTEM 



Upper Tertiary 



Lower Tertiary 



Pliocene 



Miocene 



Oligocene 



Eocene 



o 



'-5 Pi 



S3 



12 ° 



Lafayette 

 (Pliocene?) 



Waccamaw 



Chesapeake 



fl w x 



8 .a 1 | 



O ^ ,fl c3 



>h co O O 



-fl 33 



"S fl 



fl^ 



T3 S3 



Castle Ilayne 



Trent 



Nanjomoy 



Aquia 



13 



la 







Citronelle 



Caloosahatchee 

 (Florida only) 



Jacksonville and 

 Choctawhatchee 



(Florida) 

 Pasoagoula 



(Alabama) 



Oakville 

 (Texas) 



J3 



8 M 



a.2 



Jackson 

 Claiborne 



Wilcox 

 Midway 



(1 

 o 



13 



h-l 



I 



? 



Blanco 

 Republican River 



Loup Fork 

 Florissant 



Arikaree 



> 



Uinta 



Green River 

 Bridger (San Juan?) 

 Wasatch 

 Wind River 



Fort Union 



-O 83 

 o:fl 



a -a 



Merced 

 San Diego 



San Pablo 

 Santa Margarita 

 Monterey 

 Vaqucros 



San Lorenzo 



Tejon 

 Martinez 



It should be distinctly understood that exact correlations of 

 the various formations in these widely separated regions are not 

 meant to be implied in the above table. 



