120 THE GEOLOGY OE PKIACE GEORGe's COUNTY 



been transformed to a gently rolling snrface or has been lost alto- 

 gether. At Charlotte Hall, a short distance beyond the southern 

 margin of the connty, this scarp is preserved in nearly its original 

 sharpness. It is also visible south of Bryantown in Charles County 

 and north of Aquasco. In all these localities the original scarp was 

 low, not exceeding 20 feet in height, but at Congress Heights, south 

 of Anacostia River, the scarp separating the Lafayette and Sunder- 

 land surfaces is over 60 feet high and is the finest and best define<i 

 of all the ancient escarpments of this portion of the Coastal Plain. 

 At Congress Heights the surface of the Lafayette plain lies at an 

 altitude of about 2G0 feet. From this height a steep slope descends, 

 cutting through the Lafayette and underlying Miocene beds, to the 

 200-foot contour, where the broad Sunderland plain abuts against 

 the scarp and slopes gently away from it. The Sunderland forma- 

 tion is also usually separated from the Wicomico formation by a 

 well-pronounced scarp; this is discussed in the section following, 

 which is devoted to the Wicomico. 



As already stated, the Sunderland plain stands at a height of 200 

 feet near Anacostia and of 180 feet at Charlotte Hall, 30 miles to 

 the southeast. The surface of this plain thus slopes southeastward 

 at the rate of 8 inches to the mile. It also slopes gently toward the 

 larger estuaries. 



PaIcoiih)Ior/ic Character. — ISTo fossils have been discovered in the 

 deposits of Sunderland age in Prince George's County, though plant 

 remains have been found at several places in the State. A few miles 

 to the east of the Patuxent River a typical Sunderland plant bed is 

 exposed along the Chesapeake Beach Railroad in the extreme south- 

 west corner of Anne Arundel Count}' between Wilson and Owings 

 Station. At this place a plant bed occurs at the base of the deposit. 

 It consists of a stratum of black clay about ?> feet in thickness, in 

 which are numerous small ligiiiti/.c(l stems. 



Thicliness. — Although the materials of the Sunderland lie at vary- 

 ing elevations above sea level in Prince George's County, the thick- 

 ness of the formation is not great at any point. That the deposits 

 were laid down on a slotting and dissected plain is proved by many 



