-MAKYLANU GEOLOGICAL SURVEY 63 



x\s the Sunderland terrace witliin Calvert County is topographically 

 and geologically continuous with the Sunderland, which in Anne Arun- 

 del and St. Mary's counties surrounds the Lafayette, it is probable that 

 the Lafayette formation was removed from the surface of Calvert County 

 in great measure by the erosion and advance of the Sunderland sea. 

 At the time of which we are speaking, Calvert County was considerably 

 lower than it is to-day, and little by little as the Sunderland sea tore 

 away the edges of the Lafa3'ette formation and gained on the land, the 

 surface of Calvert County disappeared beneath the water. This advance 

 of the sea by erosion was also probably aided by gradual subsidence. As 

 a result of this combined movement, Calvert County was finally inun- 

 dated by the sea and its surface was covered by a formation of clay, sand, 

 and gravel which is now known as the Sunderland terrace. 



THE WICOMICO STAGE. 



After the Sunderland terrace had been deposited, the surface of Cal- 

 vert County was once more elevated above the surface of the ocean and 

 the new land area thus presented was immediately attacked by waves and 

 rivers, and the principal streams within Calvei't Comity, enumerated 

 above, came into existence and eroded extensive valleys in the surface 

 of the terrace. 



It is probable that the valleys of the Potomac and I'aluxent rivers, 

 together with tlieir larger tributaries, were cut during the post-Lafay- 

 ette uplift and that the trough in which Chesapeake Bay now lies was 

 also excavated by the Susquehanna Eiver which flowed down from the 

 north and out to the ocean somewhere in the vicinity of the present 

 nutlet of Chesapeake Bay. It is not probable that at the tinu^ of which 

 we are speaking these depressions were cut to their present de[)th. They 

 have apparently been deepened during each successive uplift. 



After the Sunderland terrace had been exposed for some time to the 

 erosive work of the elements, the surface was again lowered beneath the 

 water, but not to the extent to which it had been during the Sunderland 

 stage. The waters of the Patuxent Eiver and Chesapeake Bay advanced 

 gradually up the valleys as the land was lowered and transformed many 



