Middle Atlantic Coastal Plain. 501 



Altitude and character of seaward boundary. — The altitude 

 of the formation along the seaward boundary in northern 

 St. Mary's County is not over 200 feet while farther north- 

 ward in Maryland, due to the more extensive later Pleistocene 

 encroachments of the sea in those areas resulting in the re- 

 moval of the deposits along the seaward face, elevations of 

 240 feet are found at Marriott Hill, Anne Arundel County, 

 and 300 feet on Elk Neck, Cecil County. Clearly defined 

 escarpments appear in many places along the seaward margin 

 although at other points such escarpments are wanting, the 

 higher .terrace presenting a long featureless slope along its 

 front which gradually coalesces with the next terrace level. 

 A significant feature is found near Charlotte Hall in St. Mary's 

 County where a seaward-facing escarpment extends entirely 

 across the divide of the peninsula of southern Maryland and 

 separates the Brandywine from the lower terrace level of the 

 Sunderland. The Sunderland plain also passes at this point 

 between two of the outliers of the Brandywine and over the 

 divide between two small streams rising within the area. 



Hate and direction of slope of surface. — The slope of the 

 Brandywine surface within the main area of outcrop in the 

 peninsula between the Potomac and Patuxent rivers is some- 

 what over five feet to the mile, although it is greater nearer 

 the landward margin than seaward. In the former case the 

 slope reaches 15 feet or more to the mile in the vicinity of the 

 District of Columbia, a feature also shown to the northward in 

 Baltimore and Cecil counties, Maryland, while nearer the sea- 

 ward margin it declines to about three feet to the mile in 

 southern Prince George's and northern St. Mary's counties. 



The direction of slope is from northwest to southeast at 

 right angles to the coast lines of the period. 



Amount of dissection. — The Brandywine formation is exten- 

 sively dissected, the largest continuous area of outcrop being 

 found in the interstream area between the Potomac and 

 Patuxent rivers. Here the margin of the formation has been 

 extensivel}' dissected, resulting in many outliers. In Prince 

 George's and Charles counties, Maryland, however, are undis- 

 sected and undrained tracts possessing the essential features of 

 the old terrace surface and appearing today as broad and 

 nearly featureless plains. This is best seen in the area extend- 

 ing from Cheltenham, Prince George's County, southward to 

 Hughesville and Waldorf and somewhat beyond, into Charles 

 County, Maryland. 



Component materials and structure of deposits. — The 

 Brandywine formation is composed of gravel, sand, and loam. 

 Over considerable areas the gravel is found occurring in greater 

 abundance at the base, while sand and loam more especially 



