MARYLAND GEOLOGICAL SURVEY 83 



attitude has been partly brought about by deformation, while much of 

 it must be attributed to the original attitude in which the Lafayette 

 was deposited. 



Character of Materials. 

 The materials which compose the Lafayette formation in St. Mary's 

 County consist of clay, loam and fine gi-avel. In the railroad cutting 

 which passes through the formation at Charlotte Hall there is exposed 

 about 20 feet of a brownish-clay loam locally changed to a reddish color 

 and bearing fine gravel scattered throughout in ill-defined layers. In 

 other places beyond this county, where the Lafayette is typically de- 

 veloped, the gravel is much coarser and a bipartite division is discernible 

 whereby the finer materials are more abundant toward the top and 

 the coarser toward the bottom of the gravel, although the gravels are 

 frequently found imbedded in the clay and loam above, and these in 

 turn are mixed abundantly with the gravel below. There are no good 

 sections for studying this deposit in St. Marj^'s County. 



Stratigra-pliic Relations. 

 The Lafayette formation is built as a terrace, lying unconformably 

 and somewhat irregularly on the eroded surface of the Choptank be- 

 neath. Its surface constitutes the highest portion of St. Mary's County, 

 but its margins are believed to run out under and to be unconformable 

 beneath the edges of the Sunderland formation. 



Origin of Materials. 

 The materials which compose the Lafayette formation have been 

 derived from most of the older rocks in the region throughout which it 

 is developed. The clay and loams contain materials re-worked from 

 the Miocene, Eocene, Cretaceous, and decomposed crystalline rocks from 

 the Piedmont, while the gravels have largely been derived from the quartz 

 veins of the Piedmont and the gravel beds of the Potomac. 



