MARYLAND GEOLOGICAL SURVEY 97 



ette and that of tlic Sunderland are separated by a scarp similar in its 

 form and origin to those which separate the other terrace formation of 

 the Coastal Plain. 



In almost every place where good sections of Pleistocene materials are 

 exposed the deposit from base to top seems to be a unit. In other places, 

 however, certain layers or beds are sharply separated from underlying 

 beds by uneven lines similar to the irregular lines of a cross-bedded de- 

 posit. These breaks disappear in short distances, showing clearly that 

 they are only local phenomena within the same formation produced by 

 the contemporaneous erosion of shifting shallow-water currents, and in 

 closely adjoining regions they seem to have no relation to each other 

 Since the Pleistocene formations occupy so nearly a horizontal position 

 it would be possible to connect these separation lines if they were sub- 

 aerial erosional unconformities. In the absence of any definite evidence 

 showing these lines to be stratigraphic breaks separating two formations, 

 they have been disregarded. Yet it is not improbable that in some places 

 the waves of the advancing sea in Sunderland, Wicomico, and Talbot 

 times did not entirely remove the beds of the preceding period of deposi- 

 tion over the area covered by the sea in its next transgression. Especially 

 would deposits laid down in depressions be likely to persist as isolated 

 remnants which later were oovorod by tlio noxt mantle of Pleistocene ma- 

 terials. If this is the case each formation from the Lafayette to the 

 Wicomico is probably represented by fragmentary deposits beneath the 

 succeeding Pleistocene formations. Thus in certain sections the lower 

 portions may represent an earlier period of deposition than that of the 

 overlying beds. In those region? wlioi-c older materials arc not exposed 

 in the base of the escarpments each Pleistocene formation near its inner 

 margin probably rests upon the attenuated edges of the next older forma- 

 tion. Since lithologic differences furnish insufficient criteria for the 

 separation of these late deposits and sections are not numerous enough 

 to distinguish between local inter-formational unconformities and wide- 

 spread unconformities resulting from an erosion interval, the whole 

 mantle of Pleistocene materials occurring at any one point is referred 

 to tlie same formation. Tlic Sunderland is described as overlying the 



