THE SUNDERLAND FORMATION. 181 



deposits from the base of the Lafayette-Sunderland escarpment to the base 

 of the Sunderland-Wicomico escarpment. The few deposits of Lafayette 

 materials which may possibly underlie the Sunderland are thus disregarded 

 because unrecognizable. Similarly the "Wicomico is described as including 

 all the surface deposits extending from the base of the Sunderland- Wicomico 

 escarpment to the base of the Wicomico-Talbot escarpment. In the same 

 way it is possible that remnants of the Lafayette and Sunderland forma- 

 tions may occur beneath the Wicomico. The Talbot is described as includ- 

 ing all of the surface deposits extending from the base of the Wicomico- 

 Talbot terrace to the base of the Talbot-Eecent escarpment. It may also 

 occasionally conceal beneath its mantle of surface materials some remnants 

 of the earlier Pleistocene formations. 



The Sunderland Formation. 



Name. — The formation has been so named from its typical development 

 0^ the peninsula of Calvert County, Maryland, near the little village of 

 Sunderland. 



Lithologic character. — The materials which compose the Sunderland 

 formation consist of clay, sand, gravel and ice-borne boulders. These 

 rarely lie in well-defined beds but grade into each other vertically and 

 horizontally. The sands are frequently cross-bedded, while the clays are 

 often developed as lenses. The coarser materials commonly occupy the 

 lower portions of the formation with the finer sand and loam above, but 

 the transition from the coarser to the finer strata is seldom abrupt. Lenses 

 of gravel occur in the upper loam, while beds and lenses of loam are inter- 

 stratified with the coarse sand and gravel below. The erratic ice-borne boul- 

 ders are scattered throughout the formation and may occur in the gravel beds 

 near the base of the formation or in the loam above. As in the ease of the 

 Lafayette formation, the coarse materials are much more abundant in the 

 vicinity of the larger streams of Sunderland time which transported the 

 gravels from the Piedmond Plateau and the Appalachian region beyond to 

 their present resting place. 



That the Potomac Kiver was in existence at that time and emptied its 

 waters into the ocean or a wide estuary in the vicinity of Washington is 

 proved by the coarse sediments that are found in that vicinity. The waves 

 along the shore distributed much of the material brought down by the 

 streams but were not strong enough to transport the coarse material to any 

 great distance from the stream mouths. 



