METHODS — GEOLOGICAL 



17 



different classification. The South American formations are 

 given in a separate table, as it is desirable to avoid the appear- 

 ance of an exactitude in correlation which cannot yet be at- 

 tained. 



CENOZOIC ERA 



[ Recent epoch 

 Quaternary period I Pleistocene epoch = Glacial and Inter- 

 [ glacial stages. 



Pliocene epoch 



Miocene epoch 



Oligocene epoch 



Eocene epoch 



Paleocene epoch 



Tertiary period 



Continuing the subdivision of the Tertiary period still 

 farther, we have the following arrangement : 



TERTIARY PERIOD (North America) 



Pliocene 



Upper 

 Middle 



Lower 



Upper 

 Miocene Middle 

 Lower 



Oligocene _ 



[ Lower 



Upper 

 Eocene Middle 



Lower 



Paleocene \ ^ 



[ Lower 



Wanting 



Blanco age 



Thousand Creek age 



Snake Creek age 



Republican River age 



Loup Fork age 



Deep River age 



Arikaree age 



John Day age 



White River age 



Uinta age 



Bridger age 



I Wind River age 



[ Wasatch age 



Torre ion age]-_ , __ . 

 „ •• ^ Fort Union 

 Puerco age J 



