-1.5-meter level. Cores 31 and 29 are finer than the other cores and 

 only core 32 shows a marked trend (upward coarsening). Core 29, which 

 was obtained from a small detached shoal at the northern end of Ocean 

 City shoal, has an unusual lack of variation in mean grain size. Verti- 

 cal size trends in cores 57, 52, and 34, collected along one of the 

 ridges or arms of Ocean City shoal, are essentially dissimilar, with 

 two exceptions. Cores 52 and 34 both contain a coarse layer or event at 

 -1.8 meters, and from that level to the surface, all three cores show a 

 subtle upward-fining trend. 



Despite the diverse nature of these mean size versus depth curves, 

 some generalizations can be made about their characteristics and trends. 

 Two-thirds of the cores are dominantly medium sand; the rest are fine 

 sand. About one-third show a distinct upward coarsening, one-third show 

 a subtle upward-fining trend, and one-third no apparent trend at all. 

 The coarsening trends are usually more obvious than the fining trends. 

 At least one, core 54, shows a coarsening trend overlying a fining trend. 

 Cores collected along transects of individual shoals can occasionally be 

 correlated on the basis of a single fine or coarse layer or event. No 

 other textural patterns occur along shoal transects. Finer sands occur 

 at both the southern and northern end of shoals, as do cores showing the 

 least or most variation in mean grain size within a shoal. 



An examination of the grain size from only the upper part of the 

 cores shows a pattern of upward increase in grain size to be more appar- 

 ent than for the whole core (Fig. 41). Considering only the upper 

 (exclusive of the disturbed surface sample) trend or slope of data points, 

 7 of the 13 cores show definite upward coarsening, compared to only 2 

 which show upward fining; 4 of the cores have no distinct pattern. Sam- 

 ples from the shoreface and shoreface shoals, however, do not display 

 this pattern. Of the 13 cores (Fig. 42), 4 do not have sufficient data 

 for evaluation. Only two cores each show upward fining and upward coars- 

 ening and five cores show no distinct vertical trend in grain size. 



VII. SUMMARY 



The northern Delmarva Inner Continental Shelf has a complex bathy- 

 metric configuration largely shaped by Holocene and modern marginal marine 

 (fluvial, estuarine, coastal, shallow shelf) processes. The morphology 

 of the region is dominated by the large shelf valley of the ancestral 

 Delaware River and estuary and a linear-shoal field composed of individual 

 shelf and shoreface shoals and bracketed by a large shoal-retreat massif 

 off Cape May, New Jersey, and a small one off Chincoteague, Virginia. The 

 controlling influence in forming these major morphologic elements was the 

 Holocene eustatic sea level rise. 



Shallow subsurface strata consist of gently dipping Neogene sedimen- 

 tary beds that conform to the gentle dip gradient (1 on 8,000) and 

 direction (east and southeast) of the Atlantic Coastal Plain and that 

 display no evidence of tectonic deformation (folding or faulting) . Eleven 

 major acoustic surfaces, some of which are correlative with stratigraphic 



103 



