On profile B-B', off Ocean City, the shoreface has approximately the 

 same steepness, but its otherwise smooth configuration is interrupted 

 locally by "bulges" or shoreface shoals. Seaward of the shoreface, iso- 

 lated linear shoals are common on the inner shelf. Profile C-C, off 

 southern Assateague Island, is similar to B-B 1 in most aspects. Individ- 

 ual shoals show as much as 10 meters (30 feet) of relief. Profile D-D', 

 off the chain of small barrier islands, shows some distinct changes from 

 preceding profiles. The shoreface has a more gentle slope and the tran- 

 sition to the inner shelf ramp is less marked. Individual shoals are 

 poorly defined and do not exhibit much relief. Profile E-E', at the 

 southern end of Delmarva, represents the smoothest profile of the region. 

 The shoreface slope is more gentle than the more northern profiles and 

 the entire shelf surface is relatively featureless. 



3. Delaware Inner Shelf . 



The morphology of the Delaware inner shelf owes its origin to the 

 influence of the adjacent headland coast and the proximity of the Dela- 

 ware estuary. The Atlantic coast of Delaware, approximately 35 kilometers 

 (21 miles) long, comprises the headland section of the Delmarva Peninsula 

 (Fig. 8). It is composed of headland beaches (Rehoboth and Bethany Beach 

 areas) , baymouth barriers (extending across the mouths of Rehoboth and 

 Indian River Bays), and a small northward-growing spit (Cape Henlopen) . 



The ancestral valley of the Delaware River and estuary trends south- 

 east from the present bay mouth and diagonally cuts the inner shelf. 

 Seaward of the shelf valley lie remnants of former estuary mouth shoals, 

 also termed a shoal-retreat massif, which are similar in origin to the 

 present-day shoals (McCrie, Overfalls, Somer, etc.) lying south of Cape 

 May, New Jersey (Fig. 8). Swift (1973) examined the morphology of 

 Delaware Shelf Valley and concluded that it "reflects mainly its shallow 

 marine stage of evolution, rather than the earlier subaerial stage." 

 Hence, the shelf valley may be genetically classified as a flood-channel 

 retreat -path (Swift, 1973). Evidence for this interpretation is based on 

 an evaluation of modern topography and processes and on the discovery of 

 the ancestral, subaerial fluvial channel lying stratigraphically lower 

 and laterally offset from the present shelf valley (Sheridan, Dill, and 

 Kraft, 1974). The topographic evidence consists mainly of the apparent 

 similarity of the shelf morphology with the present-day estuary mouth. 

 The shelf valley is continuous with the flood tidal channel in the mouth. 

 The series of large shoals extending across the shelf parallel and north 

 of the shelf valley is an apparent predecessor to the large shoal complex 

 (McCrie, Overfalls, Sommer, etc.) lying south of Cape May (Fig. 8). This 

 shoal complex has been referred to as a cape platform by Field and Duane 

 (1976) and is analogous to the north side of the Chesapeake Bay entrance. 

 Caldwell (1966) estimated that the volume of littoral drift (sediment 

 transported alongshore by littoral currents) delivered to the Cape May 

 shoreline is 536,000 cubic meters (700,000 cubic yards) annually. 



Landward of the shelf valley the Delaware shelf is relatively feature- 

 less, with the exception of five distinct features: Hen and Chicken shoal . 



29 



