MARYLAND GEOLOGICAL SURVEY 121 



This has not taken place. The Talbot-Wicomico scarp is the most con- 

 spicuous topographic feature of the Eastern Shore. 



Another explanation which may be offered is, that these various terraces 

 were cut in the underlying Tertiary formations during pauses in the 

 uplift of the region and then carried beneath water-level by a subsidence 

 to receive the load of loam, sand, and gravel. In reply to this suggestion 

 it may be said that terraces cut during an uplift in the loose deposits of 

 the Tertiary formation would surely be destroyed during a period of 

 ordinary subsidence. Unless this subsidence was a remarkably rapid one, 

 the waves of the advancing sea would completely obliterate these various 

 terraces, and leave the surface in the form of a plain to receive the sedi- 

 ment of the surficial formations. It may be remarked here that the 

 Coastal Plain has been several times elevated and depressed and wherever 

 the unconformable contact is seen between two formations, it is found 

 to be a plain and not a series of terraces. Granting, however, that the 

 subsidence which carried down this terrace was extremely rapid, the sub- 

 sequent deposition would have filled up the angles between the scarp and 

 the subjacent plain as a snow storm fills up the irregularities on the 

 ground. In place of having a veneer of gravel covering the irregulari- 

 ties there would be produced a plain surface in which no terraces would 

 appear. More than this, the reentrants which penetrate the surfaces of 

 the various terraces would also be filled solid with material and would not 

 present as they do now, flat valley floors continuous with the surface of 

 the main body of the formations without. Another objection to this 

 theory is that the formations do not lap down over these terraces, but each 

 one is cut off distinctly by the scarp. Subsequent erosion has occasion- 

 ally filled up the slopes at the foot of this escarpment with talus derived 

 from the gravels above, but where this is absent, it is seen that the gravel 

 which caps the top of an escarpment is distinct from that which occurs 

 at the base. 



Geological History. 



If the methods of interpretation of the various formations have been 

 well founded, the salient features of the geological history may be estab- 

 lished with some degree of confidence. 



