198 GEOLOGY. 



ish-water origin, and the latter those of (a) lacustrine, and (b) sub- 

 aerial origin (fluvial, pluvial, eolian). The last are probably more 

 important than has commonly been recognized. 



The marine Eocene beds are confined to the borders of the con- 

 tinent; the brackish- water formations are known in Washington and 

 Oregon, while the lacustrine and subaerial deposits are found in many 

 places in the mountains of the west, and on the plains adjacent to 

 them. 



The Eocene formations are like the Cretaceous in that they are, 

 in most parts of the continent, largely unindurated. Many of them 

 are still in the condition of sand, gravel, clay, etc., much as when 

 deposited. Locally, they have been indurated, and still more locally, 

 metamorphosed. 



The Eastern Coast. 



The Atlantic coast. — The Eocene formations of the Atlantic and 

 Gulf coasts appear at the surface at intervals along a belt of varying 

 width from New Jersey to Texas. The beds dip toward the coast 

 (Fig. 380), and from the areas where they appear at the surface, they 

 are continued seaward beneath younger beds. 



In the Atlantic Coastal plain, the Eocene beds are separated from 

 the underlying Cretaceous, by an unconformity. They represent the 

 incursion of the sea over at least a narrow area from which it had with- 

 drawn at the close of the Mesozoic. The materials of the Eocene 

 appear to have been derived largely from the Cretaceous, but sedi- 

 ments from farther inland were contributed by the drainage from 

 the highlands and mountains to the west. Clays, sands, and green- 

 sand (glauconitic) marls are the most common materials of the Eocene 

 of this province, and the conditions of sedimentation appear to have 

 been much the same as during the Cretaceous. 



Until recently, attempts to correlate the Eocene sections of the 

 different parts of the Atlantic and Gulf coasts were not altogether 

 successful, and it is still common to speak of the Lower, Middle, and 

 Upper portions of the system in a rather general way. 



In New Jersey (Shark River marl) x and Maryland 2 (Aquia and 



1 Ann. Rept. State Geologist of New Jersey for 1893 and, earlier years. 



2 Clark and Martin, Maryland Geol. Surv., Volume on the Eocene. The Eocene 

 of this region is sometimes called the Pamunkey series. 



