the Middle Atlantic Slope. 38B 



and on the marginal portion of the Piedmont zone at altitudes 

 reaching 250 feet or more. It consists of great beds of well 

 rounded quartzite cobbles a foot or less in diameter, together 

 with many smaller pebbles, generally imbedded in reddish loam. 

 A representative locality is the plateau (100 to 150 feet above 

 tide) between Harlingen and Rocky Hill and five or six miles 

 north of Princeton, where, over an area of several square miles, 

 well rounded quartzite cobbles cumber the fields and are 

 heaped up along the lanes in great winrows sufficient to fence 

 the farms and pave the roads. 



3. The type of the deposit into which the deltas commonly 

 merge is a confused and heterogeneous mass of sand, gravel, 

 and pebbles of obscure or inconstant structure, the materials 

 evidently derived in larger part from the sub-terrane and in 

 smaller part from the contiguous deltas, and the thickness 

 ranging from a foot or two to perhaps fifteen or twenty feet. 

 In the south the materials are predominently fine, comprising 

 sand, clay and silt interspersed with occasional pebbles up to 

 three or four inches in diameter, with a few intercalated sheets 

 of gravel ; while in the north the deposit is predominently 

 coarse and gravelly, especially toward the northern extremity 

 of the Coastal plain where it has been recognized by Cook, Lewis 

 and Chester as "Southern Drift," "Yellow Gravel," "Dela- 

 ware Gravels," etc. ; and in a general way it varies in coarse- 

 ness and in thickness from the fall-line to the coast, the thick- 

 ness increasing and the coarseness diminishing seaward. This 

 is by far the most extensive type of the deposit ; it covers 

 perhaps three-fourths of the area of the Coastal plain ; but 

 despite its vast extent, good exposures are uncommon. Those 

 at Ordinary Point on Sassafras river, in northern New Jersey, 

 and on Long Island (described elsewhere by the writer, Cook 

 and Merrill, respectively), are, however, representative of the 

 latitudes in which and the altitudes at which they occur. 



4. At low levels, especially along the coast, the deposit be- 

 comes fine, assumes moderately regular stratification, attains 

 considerable thickness, and yields recent fossils. This type 

 has been described by W. B. Rogers in eastern Virginia, Tyson 

 in peninsular Maryland, Booth and Chester in southern Dela- 

 ware, Conrad in New Jersey and southern Maryland, Merrill 

 on Long Island, and others in different localities, and does not 

 require extended notice here. 



Summarily, the intern 1 u vial phase of the formation consists 

 of a mantle of either heterogeneous or definitely assorted and 

 deposited material, largely local but partly erratic, overspread- 

 ing the Coastal plain (except along the water ways), from the 

 Roanoke to the Raritan, and encroaching upon the Piedmont 



