MARYLAND GEOLOGICAL SURVEY 87 



by an abrupt change. The coarser materials are frequently found above 

 in the loam and the finer materials below in the gravel. Many of these 

 materials are in an advanced stage of decay. 



Stratigraphic Eelations. 



The Sunderland formation is bnilt as a terrace, lying unconformably 

 and somewhat irregularly upon the older ]\Iiocene and Lafayette de- 

 posits. This terrace was laid down about the margin of the Lafayette 

 formation and the attenuated edges of the latter are believed to run 

 out unconformably for a short distance beneath it. At Charlotte Hall 

 the Sunderland formation is separated from the Lafayette by a well- 

 defined scarp about 20 feet in height which resembles topographically 

 a wave-cut cliff, softened by subaerial erosion. The surface of the Sun- 

 derland formation forms the surface of the high divide of St. Mary's 

 County, except along its margin, where it seems to pass beneath the 

 Wicomico as the margin of the Lafayette does beneath the Sunderland 

 at Charlotte Hall. 



A word may be added regarding the scarp at Charlotte Hall, as it 

 seems to have been overlooked by former geologists. The height of the 

 scarp is about 20 feet and separates the flat surface of the Lafayette 

 above from the plain surface of the Sunderland below. The Lafayette 

 surface stretches away in an unbroken plain, gently rising toward the 

 Piedmont, and the Sunderland extends southward toward the ocean. 

 Jnst beyond the main scarp-line there are in the vicinity of Chai'lotte 

 Hall a number of outliers of Lafayette which rise above the general 

 flat of Sunderland. These bear the same relation to the main Lafayette 

 deposit as the outliers of the Talbot formation, which now rise above the 

 surface of Chesapeake Bay, bear to the mainland close by. This topogra- 

 phy at Charlotte Hall might be easily overlooked by one making a 

 hurried reconnaissance, and might be entirely misunderstood by one 

 unaccustomed to the geology of the Coastal Plain. The narrow, flat re- 

 entrants which separate the main body of the Lafayette from the out- 

 liers might be looked npon as a valley cut by stream erosion and the 

 presence of opposing scarps where the outliers face the main body of 



