26 



they occupy in the following order : At the top, Lafayette ; then, on 

 a middle terrace, the earlier Columbia, and farther down the later 

 Columbia. This indicates clearly that the successive submergences 

 were slighter and slighter. Along the coast and back from the 

 stream channels these formations are not developed in terraces so 

 plainly, but in a more continued series with an erosion break be- 

 tween the Lafayette and the earlier Columbia. 



The latest division of the surficial deposits of the Pleistocene in 

 Maryland is threefold : Sunderland, Wicomico and Talbot. The 

 Sunderland is considerably developed in Prince George's, Charles, 

 St. Mary's and Calvert counties, lying against the Piedmont or 

 lapping around the edges of the Lafayette. The material composing 

 it consists of gravel, sand and loam, containing occasional bowlders. 

 The base of the Sunderland is about go feet above tide, and in places 

 reaches 170 feet above tide. The Wicomico consists structurally of 

 material very much like that of the Sunderland, but the proportion 

 of sand and loam is larger. The base of this formation is about 

 forty to fifty feet above tide level in southern Maryland, but higher 

 in altitude to the north. The Talbot formation is a terrace of vary- 

 ing width, lapping around the edges of the Wicomico, attaining a 

 height of thirty to fifty feet. Any sort of material that enters into 

 the composition of the other terraces may be found in the Talbot, 

 but the percentage of loam is greater, and it also contains lenses of 

 greenish-blue clay, in which are embedded plant remains. The Corn- 

 field Harbor clays, carrying remains of marine and brackish-water 

 animals, and also similar deposits five miles south of Cedar Point 

 are referred to the Talbot formation. This is an instance of the grad- 

 ing over of the Columbia sands of the region back from the coast 

 into the littoral or low-level Pleistocene. The base of the Talbot 

 terrace is irregular, lying above tide at some places and below at 

 others, but the top where it borders the sea cliff is usually limited 

 by the forty-five or fifty foot contour. Large areas of Wicomico and 

 Talbot have been mapped on the "western shore" of Maryland, but 

 it is on the "eastern shore" that they attain their most marked de- 

 velopment. 



The following, according to Shattuck 1 , may have been the order 

 and extent of the later Coastal Plain formations in Maryland : Mio- 

 cene elevation and erosion ; subsidence and deposition of Lafayette ; 



1 "The Pleistocene Problem of the Northern Atlantic Coastal Plain" (Am. 

 Geol., Vol. XXVIII, pp. 87-107, iqoi). 



