MARYLAND GEOLOGICAL SUEYEY 115 



an altitude of about 200 feet. This shows, therefore, a difference 

 of 100 feet in 30 miles, or a surface slope toward the sea of about 

 3 feet to the mile. So slight and gradual a decline in elevation 

 might be attributed to the original attitude of the material when it 

 was deposited Avere it not for the fact that the Sunderland terrace, 

 Avhich wraps about the base of the Lafayette, has suffered a deforma- 

 tion of 20 feet, or about 8 inches to the mile, throughout the same 

 region, and the Wicomico appears also to have been affected by a 

 slight tilting. It is probable, therefore, that the present slope of the 

 Lafayette formation is due partly to its original attitude and partly 

 to subsequent tilting. 



Paleontologic Character. — Fossils are practically lacking in the 

 Lafayette deposits of the Atlantic Coast region none being found in 

 this area. Pebbles containing Paleozic fossils are present in the 

 formation at many places throughout the district, but are of impor- 

 tance only because they show the source of the materials. 



Thickness. — The thickness of the Lafayette is somewhat variable. 

 In its northwesternmost exposures the formation shows a thickness 

 of 3 to 10 feet, the amount increasing somewhat toward the south- 

 east. Over the broad plain in the vicinity of Brandywine the Cal- 

 vert, which is the next subjacent formation, is reached at a depth of 

 about 28 feet. The maximum thickness of the Lafayette in this 

 county probably does not exceed 40 feet. 



Stratigraphic Relations. — A very marked unconformity separates 

 the Lafayette from all underlying formations. In one place or 

 another within the Coastal Plain province it overlies almost every 

 older formation represented in the region, and thin remnants are 

 present in many places on the eastern borders of the Piedmont 

 Plateau. In Prince George's County it rests mostly upon the Cal- 

 vert and Choptank formations and is, in the main, a surface deposit, 

 although locally it in all probability dips beneath beds of Pleistocene 

 ae-e. 



