44 the eocexe deposits of ^akylaxd 



Geneeal StkatictEaphic Eelatioxs. 



Our knowledge of the Tertiary geology and paleontology of the Middle 

 Atlantic Slope has been largely increased since the days of Conrad and 

 Eogers, yet few fields have afforded better opportunities in recent years 

 for continued investigation, since very divergent opinions have prevailed 

 and even to-day find expression in the ditt'erent interpretations of the 

 data. 



Both the Eocene and the Xeocene divisions of the Tertiary in this 

 area have broad surface exposures, and are represented by character- 

 istic sections along the leading waterways. Both are also highly fossilif- 

 erous, although the Xeocene shows a greater diversity of species than 

 does the Eocene. This difference, however, is not so great as one would 

 infer from a perusal of the literature, since a large number of Eocene 

 species, many of them very common, have been until recently unrecog- 

 nized, or at least unrecorded. 



A brief discussion of the general relations of the Coastal Plain de- 

 jDOsits in the Middle Atlantic Slope is essential to a clear comprehen- 

 sion of the Eocene formations. A more detailed history of the several 

 groups of deposits will be found in other volumes of the Survey. 



The Coastal Plain consists geologically of a series of formations that 

 were deposited as moderately thin sheets, one above another, along the 

 eastern border of the crystalline belt, elsewhere referred to as the Pied- 

 mont Plateau. The coastal deposits are slightly inclined eastward, so 

 that successively later members of the series are encoimtered in passing 

 from the interior of the country toward the coast. 



From the beginning of deposition in the coastal region until the pres- 

 ent time sedimentation has apparently been constantly in progress over 

 some portions of the area. Differential movements of the sea-floor, with 

 its accumulated sediments, took place, however, from time to time, so 

 that the formations present much complexity along their western mar- 

 gins. It is not uncommon there to find certain members of the series 

 lacking, as renewed deposition carried a later formation beyond its pre- 

 decessors. In the absence of distinctive fossils, the discrimination of 

 the different horizons at such points is often attended with great un- 

 certainty. 



