EOCENE 497 



older ranges, but merely to the youth of the former ; denudation 

 has not yet had time to sweep them away. 



The Tertiary system or period is divisible into four quite well 

 distinguished series or epochs, which may usually be identified 

 in both the marine and fresh-water formations ; but for lack of 

 common fossils it is not yet possible to correlate the stages and 

 substages of the interior region with those of the coast. In the 

 preceding table, therefore, no exact comparison of these minor 

 subdivisions is intended. 



It has become customary to distinguish between the older and 

 newer parts of the Tertiary by grouping together the Eocene and 

 Oligocene into the Palaeogene, and the Miocene and Pliocene into 

 the J\ r eogene. Eocene and Neocene are employed in the same 

 way, but this is objectionable because it is using Eocene in two 

 different senses. 



The Eocene Epoch 



The name Eocene is derived from two Greek words, — eos, 

 dawn, and kainos, recent, — and was, like the names of most of 

 the other Tertiary epochs, proposed by Lyell. 



American. — Along the Atlantic and Gulf borders the coast-line 

 of the Eocene closely follows that of the Cretaceous, of which only 

 a narrow strip separates the Eocene from the Triassic and crystal- 

 line rocks of the Piedmont plain. The unconformity between the 

 Cretaceous and Eocene indicates that along this coast the latter 

 period had been inaugurated by an encroachment of the sea upon 

 the land. The Mississippi embayment had nearly the same size 

 and form as before, extending up to the mouth of the Ohio. 

 Florida was entirely submerged, as was most of Central America, 

 cutting off the northern from the southern continent. On the 

 Atlantic coast the Eocene rocks are unconsolidated sands and 

 clays, with some glauconitic greensand, particularly in New Jersey. 

 They form a narrow belt through New Jersey, Maryland, and Vir- 

 ginia, widening into a quite broad band through the Carolinas 

 and the Gulf States, and extending around the borders of the 

 Mississippi embayment into Texas. In the Gulf region the rocks 



