Table 6. Coast Guard Core Descriptions* 



Core No. 



Interval (ft) 



Sediment Description 



B-l 



0to9 



Sand; gray fine to medium with shells 





9 to 26 



Sand; grayish brown, fine to medium with trace of gravel 



B-9 



Oto 15 



Sand; grayish brown, medium to coarse with traces of gravel 





29 to 32 



Sand; brown, medium to coarse with traces of gravel 



B-17 



Oto 5 



Sand; dark gray, fine to medium with organic silt and shells 





5 to 18 



Sand; dark gray, fine to medium with shells 





18 to 26 



Sand; grayish brown, fine to medium, traces of gravel 





26 to 34 



Sand; gray, fine to medium 



J 



34 to 39 



Sand; yellowish brown, fine to medium 



*Data from Alpine Geophysical Associates, Inc. (1969). (See Figure 2 for locations.) 



Area C (separate from Area B) is an unusual north-south trending sedimentary basin, 

 described in Section II. Closely spaced geophysical lines show the region underlain by 

 complex crossbed sedimentary structures. (See Figures 7 and 8.) Core 2 reveals that the 

 uppermost 2 yards of sediment (the core length) is fine to coarse clean sand. Boring log 2 

 (Table 2) for the Coast Guard Scotland Light structure indicates that the entire thickness of 

 crossbed material (mean thickness about 15 yards) consists of alternating fine to medium 

 sand, silt, and pea gravel. Coast Guard core B-l (Table 6) on the western side of the area 

 shows a sand thickness of 26 feet, the entire core length. Using a figure of 13 yards as a 

 minimum thickness, the computed volume of potential borrow material for Area C is 

 approximately 645 X 10 6 cubic yards. 



Borrow Area D is the southernmost of the four areas, separated from Areas B and C by 

 Shrewsbury Rocks. Shrewsbury Rocks result from Coastal Plain strata cropping out on the 

 sea floor, and in places are covered by only a thin veneer of residual sand and gravel. For 

 this reason, the region between Areas B and D should be avoided as a borrow site. In 

 Area D, Coastal Plain strata are also close to cropping out on the sea floor. The data from 

 cores 80 and 81 indicate a recoverable sand thickness of about 1 yard from the shoreface 

 out to the 80-foot depth contour. The calculated sand volume for Area D is 42 X 10 6 cubic 

 yards. The southern boundary of Area D is arbitrarily picked as the southernmost limit for 

 this study; it is not intended to necessarily define the actual limit of potential borrow sand. 



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