82 THE EOCEXE DEPOSITS OF MAEYLAXD 



COERELATIOX OE DEPOSITS. 



jSTiimerous attempts have been made to correlate the Eocene deposits 

 of Maryland with those of other areas. ]^ot only has the attempt been 

 made to establish the equivalency between the Maryland deposits and 

 those of adjoining states to the north and sonth, but also with the more 

 distant Gulf region and with Europe. That the conclusions reached by 

 the various investigators have been widely at variance has already been 

 shown in the Historical Eeview. Some have considered the strata to 

 represent but a small part of the full Eocene series, while others have 

 regarded them to embrace a considerable portion of the same. These 

 diverse views will be discussed in detail in the subsequent pages. 



Two methods of correlation are possible, one based upon physical, the 

 other upon biological criteria. The faunal and floral characteristics of 

 the formations find, therefore, interpretation only as the physical fea- 

 tures are clearly understood since the geological and geographical range 

 of species is determined to a large extent by conditions of sedimentation. 

 The physical characteristics of a formation, therefore, bear a close 

 relationship to its contained faunas, and cannot be ignored in the corre- 

 lation of the deposits. 



It is a well-recognized fact that the most trustworthy correlations are 

 those based upon paleontological criteria, still the possibilities of varia- 

 tion in the succession of organic forms in widely separated areas are 

 so great that detailed correlation oan seldom be satisfactorily attempted 

 even where general equivalence is recognized. This is particularly 

 true of the Eocene of the Middle Atlantic Slope where, as will be 

 shown later, the range of species is quite different in certain particu- 

 lars from that hitherto recognized in adjacent provinces. Such being 

 the case, it is evident that whatever aid the physical criteria can afford 

 should be employed in the interpretation of the Maryland Eocene de- 

 posits. 



CORRELATIOISr OF THE DEPOSITS WITHIX THE MIDDLE ATLANTIC SLOPE. 



It has generally been conceded that the Maryland and Virginia 

 Eocene deposits constitute one and the same geologic province, a con- 

 clusion which is well borne out by the fact that the strata are practically 

 continuous and that the materials of the deposits and the fossils are 



