182 PHYSIOGRAPHY AND GEOLOGY OF THE COASTAL PLAIN PROVINCE. 



Much of the finer materials constituting the Sunderland deposits were 

 undoubtedly derived from the immediately underlying Cretaceous and Ter- 

 tiary beds, although no inconsiderable amount of both fine and coarse 

 debris unquestionably came from the Lafayette deposits which were largely 

 destroyed over the region of Sunderland deposition by the waves of the 

 advancing sea. 



The following section exposed near the Chickahominy Eiver north of 

 Richmond illustrates the character of the Sunderland formation. 



Section in Chicl-aJioniiiiy Eiver Valley north of Bichmond. 



Feet 



Pleistocene Brownish-yellow and mottled clay loam 4 



Band of clay containing few smaU pebbles. . . 1 

 Brown ferruginous sand mixed with clay. ... 5 

 Gravel layer with pebbles 1 to 3 inches in 

 diameter 1 14 



Miocene. Calvert Compact drab clay containing many fossil 



casts ( exposed ) 10 



Total '211/4 



Strike, dip, and tliicl-nexs. — The beds of the Sunderland are ])racf"ically 

 horizontal, the gentle dip to the southeast being very slight and due for 

 the most part to the gentle slope of the Sunderland sea floor in that direc- 

 tion, although a slight tilting since Sunderland time may have increased 

 the southeasterly inclination of the beds. The thickness of the formation 

 is occasionally 40 to 50 feet, but usually considerably less, the thickest por 

 tions of the formation representing the filling of depressions in the pre 

 Pleistocene floor. 



Stratigrap/iic relations. — Tlu' Sunderland formation throughouf the 

 Coastal Plain overlies uneonfonuably the various formations l)elonging to 

 the Potomac, Eocene, and Miocene groups. It is not improbable that the 

 edges of ];he Lafayette formation extend out beneath part of the Sunderland 

 deposits although this cannot be determined in the absence of any definite 

 line denoting a stratigraphic break and because of the similarity of the two 

 formations. It is probably overlain unconformably in certain places by the 

 Wicomico and Talbot formations as already explained. 



Paleontologic cliaracter. — J»[o fossils have been found in the Sunder- 

 land deposits of Virginia except the pebbles with Paleozoic remains derived 

 from the Appalachian region. In Maryland some clay beds containing 

 I^lant remains are found in the deposits but they are neither numerous nor 



