study of the nonbiogenic positive-relief features (referred to as shoals, 

 ridges, or bars), as evidenced by the works of Curray (1960), Jordan 

 (1962), Sanders (1962), Shepard (1963), Hyne and Goodell (1967), McMaster 

 and Garrison (1967), Uchupi (1968), Smith (1969), and Swift, et al. (1972) 

 However, it has been only recently that features on the Atlantic shelf 

 have been characterized and interpreted from a regional perspective re- 

 lating them to Holocene events, sediment sources, and modern processes 

 (Duane, et al . , 1972; Swift, et al . , 1972; Swift and Sears, 1974; Field 

 and Duane, 1976) . 



Uchupi 's (1968) study pointed out the existence of long linear sand 

 swells on the Atlantic shelf south of Long Island. Duane, et al . (1972) 

 and Swift, et al. (1972) pointed out the variation in shoal types and 

 location. Swift, et al. (1972) incorporated the shoal patterns with 

 other topographic features on the shelf and placed them in a hierarchal 

 order (Table 2). This order follows the Horton hierarchal order applied 

 in studies of fluvial morphology where the lowest number refers to the 

 primary tributary and increasing numbers are applied to the streams they 

 feed (Leopold, Wolman, and Miller, 1964). The same hierarchal order is 

 used here primarily to show the relative size and sometimes genetic rela- 

 tionship which exists between various morphologic elements of different 

 orders (first-order features are those that make up second-order features, 

 etc.) . 



Table 2. Hierarchy and occurrence of morphological elements on the 

 Continental Shelf. 



The central and southern Atlantic shelf (from Swift, et al., 1972) 



Small-scale elements 



Ripples and sand waves 



Large-scale elements 



First order: Shoreface-connected ridges and swales 

 Isolated ridges and swales 



Second order: Cape-associated shoals 

 Ridge fields 



Third order: Shoal -retreat massifs 



She If -transverse valleys 



Cuestas 



Deltas 



Scarps 



The northern Delmarva inner shelf 



First order: Shoreface-connected shoals 

 Linear isolated shoals 

 Crescentic cape shoals 



Second order: Shore face 



Linear-shoal fields 

 Shoal-retreat massifs 

 Shelf-transverse valleys 



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