MARYLAND GEOLOGICAL SURVEY 97 



remember when vessels moored and discharged their cargoes in places 

 which are now occupied by extensive marshes or meadow lands. Such 

 deposition would doubtless not have occurred if the forests had 

 been allowed to remain undisturbed, but the advent of the white man 

 and the consequent destruction of the forests exposed the loose material, 

 which forms the Coastal Plain, to the erosive effect of rain and rivers 

 with the result that rapid denudation toward the headwaters of streams 

 has been accompanied by rapid sedimentation along the lower courses. 

 Many of the larger estuaries, such as the Patuxent and St. JIary's 

 rivers and St. Jerome Creek, and St. Clement and Breton Bays, have been 

 filled in toward their heads, while shorter estuaries have been trans- 

 formed to meandering streams. The most extensive beach and dune 

 deposits are found along the Bay and Potomac shores at Point Lookout 

 and Sandy Point. Behind this obstruction, which separates the ocean 

 waters of Chesapeake Bay from an ancient irregular shore line, lie many 

 brackish water lagoons which have already been considerably filled up 

 with sediment since they were separated from the Bay. 



ORIGIN OF JIATERIALS. 



The sources from which the Sunderland, A\'icomico, and Talbot seas 

 derived the materials for their respective deposits were principally con- 

 fined to the Coastal Plain. The waves must have eroded large areas 

 of the Cretaceous, Eocene, Miocene, and Lafayette and re-worked 

 these materials into their own deposits. In addition to this, the Wicomico 

 sea had the Sunderland deposits on which to erode and the Talbot sea 

 had both the Sunderland and Wicomico land surfaces from which to 

 derive materials. Wherever the Eocene sand and marls have been used 

 in any considerable quantity, their presence is indicated by a peculiar 

 greenish color imparted to the deposit. Miocene materials cannot be 

 so readily detected, but they were, nevertheless, re-worked in large 

 quantities. The rivers also brought in contributions from the Piedmont 

 Plateau and the mountains of Western Maryland. This material was 

 pushed along the bottom, drifted in suspension and floated along on 

 ice-blocks. 



