

resulting from a locally transgressive situation would be different, 

 as elucidated by Fischer (1961), and would range from complete preserva- 

 tion to complete erasure of the barrier sequence. As discussed here and 

 in Field (1976) , the subsurface stratigraphy of the Delmarva shelf con- 

 tains a partial record of the passing of the Holocene barrier. The 

 coastline of the study area is a submerging one (Kraft, 1971; Hicks, 

 1972) and from information discussed previously, it appears that the 

 barrier is continuing to retreat. As it retreats, the sand of the fore 

 barrier is stripped off and used in back-barrier construction, inlet 

 filling, or spit progradation, and shelf sand body accumulation. The 

 barrier sequence as an entity has a short life expectancy; it continuously 

 erodes at the base along the shoreface as it retreats. 



On the northern Delmarva inner shelf, sand bodies occur in identifi- 

 able patterns in discrete areas that can be related directly to the gross 

 geomorphology . Within the Delmarva Valley are fluvial and estuarine sands 

 that can be identified by their surface and subsurface configuration. 

 North of the shelf valley lie subsurface fluvial sands overlain by estuary- 

 retreat shoals. Adjacent to the headland and baymouth barrier coast of 

 Delaware there are relatively few shelf sand bodies, and those can be 

 related genetically to ancestral, fluvial, or modern tidal processes of 

 inlets. The northern limit of the linear-shoal field nearly coincides 

 with the beginning of the long barrier island-spit comprising Fenwick and 

 Assateague Islands. Termination of the barrier at Fishing Hook Spit marks 

 the approximate southern limit of the shoal field. Field (1976) indicated 

 a zone in the center of the shoal field that is devoid of shoals which may 

 represent an ancestral stream valley, a supposition that is supported by 

 the group of buried channels that form a cluster in the vicinity of Ocean 

 City Inlet (Fig. 18) . 



The origin of the large sand shoals that lie on the Atlantic 

 Continental Shelf between Long Island and Florida is not clearly under- 

 stood. Sanders (1962), Kraft (1971), and McClennen (1973) described 

 these features as possible remnants of transgressed barrier islands. 

 From systematic studies of shoal morphology, structure, and lithology 

 (Uchupi, 1968; Duane, et al . , 1972) and investigations of sediments and 

 processes of individual ridges (Moody, 1964; Swift, Stanley, and Curray, 

 1971), it was concluded that the ridges are submarine in origin and have 

 no history as a subaerial landform. Within the past 5 years many studies 

 on these ridges or shoals, particularly those in the mid-Atlantic Bight 

 (Long Island to Cape Hatteras) , have been published and more studies have 

 been initiated. An understanding of their behavior in response to fluid 

 processes is becoming clearer, but a priori evidence for their genesis 

 is still lacking. This is due in part to the difficulty in separating 

 and identifying those processes which may have initially formed the shoals 

 versus those processes that merely modify them, regardless of the original 

 mode of formation. 



Seismic reflection profiles of hundreds of linear shoals have been 

 collected and reported by Swift, Stanley, and Curry (1971); Duane, et al . 

 (1972); McClennen (1973); Sheridan, Dill, and Kraft (1974); and Stahl, 



78 



