MARYLAND GEOLOGICAL SURVEY 127 



uplift was not apparently of long duration, and when the land sank once 

 more and admitted the Talbot sea, the depression did not much exceed 

 45 or 50 feet. This subsidence was not sufficient to submerge the Eastern 

 Shore through its entire extent and the epoch was not of sufficient dura- 

 tion to permit the waves of the Talbot sea to cut away the Wicomico 

 which formed the surface of that land mass, so the Eastern Shore re- 

 mained as a barrier throughout Talbot time and separated the waters of 

 Chesapeake Bay from those of the ocean beyond. The appearance of the 

 Coastal Plain in Talbot time is approximately represented in Plate XXX, 

 and resembled very much the appearance of the region at the present time. 

 Once more the lower courses of the larger rivers were transformed into 

 estuaries and the ice floes came down again from the mountain valleys 

 with their freight of boulders. Here mastodons roamed about the re- 

 gion and their bones have been entombed in its swamp deposits along 

 with the remains of the forest in which they lived. 



These deposits which were described above, whether they carry plant 

 or animal remains, have certain characteristics in common. They are all 

 developed as lenses in the body of the Talbot formation. Usually the 

 contact of the clay with the older formations is not visible, but its strati- 

 graphic relations are such as to leave no doubt that it, or a thin gravel 

 bed on which it occasionally rests, is unconformable on whatever lied be- 

 neath. The upper surface of these clay lenses is everywhere abruptly 

 terminated by a bed of coarse sand or gravel which grades upwards into 

 loam and this cover at its contact with the clay strongly suggests an 

 unconformity. 



The stratigraphic relation of these lenses of clay, which are invariably 

 unconformable on the underlying formation and apparently so with the 

 overlying sand and loams belonging to the Talbot formation, is a problem 

 which engaged the attention of the author until it appeared that the ap- 

 parent unconformity with the Talbot, although in a sense real, does not, 

 however, represent an appreciable lapse of time and that, consequently, 

 the clay lenses are actually a part of that formation. In order to under- 

 stand more clearly what is believed to have taken place, these clay depos- 

 its will be divided into two groups, those which carry plant remains con- 



