by the migrating coast. Much of the sedimentary record from repeated 

 transgressions and regressions has been erased by erosion during the 

 transgressive phase. Surficial sands are generated by continuing re- 

 working of older deposits, some of which represent reworking of original 

 fluvial deposits. Enormous volumes of sand are contained in the barrier 

 island chain and the surface sand unit, which includes the linear-shoal 

 field. This abundance of sand is probably due, in part, to the proximity 

 of the Delaware River which was fed in upland regions by glacial melt 

 water. The transport of sand from an external source to the coast and 

 shelf was terminated several thousand years ago, at least, when the 

 gradients of streams decreased and they became embayed in estuaries or 

 closed off by spits. 



2. Evolution of Inner Shelf Topography. 



Results from this study are applicable to understanding the Quater- 

 nary evolution of shelf topography on a shallow Coastal Plain shelf, and 

 may yield some insight into how shoals, channels, and other such features 

 originated. Most of the Atlantic shelf is mantled by sand (Milliman, 

 Pilkey, and Ross, 1972) which has originated through vastly different 

 processes in different periods of time. Even within the relatively 

 limited confines of the study area, surface sediments represent a com- 

 plex of multistory and multilateral sand bodies, each having a different 

 history of transportation and accumulation. They are pods or ribbons 

 (length to width ratios of less than and greater than 3:1, respectively) 

 and represent a near-final configuration of sands that have passed through 

 a fluvial, estuarine, and beach cycle. 



The Delaware and Susquehanna Rivers, bracketing the Delmarva Peninsula, 

 are major streams draining terrain that was directly glaciated during the 

 Pleistocene. Field and Duane (1976) hypothesized that the mid-Atlantic 

 shelf received large volumes of sand, perhaps more than the New England 

 shelf and probably more than the south Atlantic shelf, during the Pleis- 

 tocene and early Holocene. The dominant influence of streams in shaping 

 the northern Delmarva shallow shelf is quite evident from the data accu- 

 mulated in this study. Shelf topography (Delaware Valley), structure 

 (buried channels) , sediments (iron-stained gravels) , as well as the 

 lithostratigraphic record beneath the coast (climbing channel sands) 

 all document an initial surge of sediment into the study area by fluvial 

 processes (Field, 1976). Once deposited, these sediments were subject 

 to erosion and reworking, as evidenced by the absence of gravels on the 

 surface, the lack of unfilled channels, except in Delaware Bay, and the 

 presence of several overlying coastal facies. 



The role of coastal depositional processes in the evolution of the 

 inner shelf sedimentary record is important because barrier sands are a 

 volumetrically and economically important facies in the rock record 

 (Pettijohn, Potter, and Siever, 1972). However, as Davis, Ethridge, and 

 Berg (1971) point out in their comparison of Holocene, Cretaceous, and 

 Jurassic barrier environments, deposition and preservation of these 

 sediment suites presuppose a locally regressive situation. Sequences 



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