90 THE PLIOCENE AND PLEISTOCENE DEPOSITS OP MARYLAND 



valleys cut in the body of the Lafayette formation, but with the advance 

 of the Sunderland sea these drainage ways were submerged and filled and 

 the divides which separated them were either obliterated or else cut up 

 into a series of outlying islands. A similar topography may be seen on 

 the Eastern Shore of Chesapeake Bay today. 



Another line of evidence is furnished by the presence of a beach 

 gravel on the surface of the Sunderland formation as it approaches the 

 base of the Sunderland-Lafayette scarp. The Lafayette in this region 

 carries very little gravel and waves cannot produce a shingle beach unless 

 there is gravel at hand out of which to make it. At Charlotte Hall, 

 however, the waves of the Sunderland sea concentrated on the beach the 

 small amount of gravel which they secured by the erosion of the Lafayette 

 scarp. It may also be added that there are ice-borne blocks in the body 

 of the Sunderland formation beneath the scarp-line, but none have yet 

 been discovered in the Lafayette formation above. 



An even more significant feature of the topography in the vicinity of 

 Charlotte Hall is furnished by two generations of stream valleys. One 

 of these, the older, is now dry and unoccupied. It penetrates the La- 

 fayette formation and formerly drained from it into the Sunderland sea. 

 The other generation of valleys is now being rapidly extended inland 

 from the Patuxent and Potomac rivers. These latter valleys are steep- 

 walled and V-shaped and at the present time have worked their way so far 

 back on the divide as to drain the edge of the Sunderland formation in 

 the vicinity of Charlotte Hall. These two valley systems are not only 

 distinct in age, but they have no physical connection whatsoever. 



What was said in regard to the Lafayette formation forming the 

 surface of the country is also true of the Sunderland. Wherever it is 

 developed, it forms the surface of the region, with the exception of a 

 short distance around its outer margin where the Wicomico formation, 

 when present, is believed to encroach somewhat on its basal members and 

 to lie on them uncomformably. In almost every place where good sec- 

 tions of Pleistocene materials are exposed the deposit from base to top 

 seems to be a unit. In other places, however, certain beds are sharply 

 separated from underlying beds by uneven lines that seem to suggest an 



