individual particles; cementation is primarily confined to grain contact 

 surfaces . 



The void space in type G rock and the low strength of the individual 

 carbonate grains relative to quartz and many other rock-forming minerals 

 suggest that this material may be prone to failure under loading by 

 breaking of cementation bonds and the crushing of the individual carbon- 

 ate particles. This would be especially likely under high-bearing stress 

 such as occurs in pile foundations. It should be noted that skin fric- 

 tion on such piles may contribute relatively little to the bearing 

 capacity because horizontal earth pressure in a cemented medium would 

 be very small. The essentially unconsolidated facies may, in such cases, 

 provide a better foundation medium than cemented or partly cemented 

 facies. 



4. Sand Resources. 



The chief requirement for large volimies of sand-size sediment in the 

 study area is for beach restoration and nourishment on the nearby coast. 

 Sand suitable for this purpose should closely match the size distribution 

 of native beach material, be mechanically and chemically stable, and be 

 reasonably free of fines and foreign material (e.g., sharp coral frag- 

 ments) which might degrade the quality of the beach for recreational 

 purposes. Specific site locations of potential offshore sand resources 

 within the study limits have been reported in U.S. Army Engineer District, 

 Wilmington (1973) and Meisburger (1977) . 



Previous studies of the Atlantic inner shelf sediments indicate that 

 suitable sand occurs most commonly in offshore shoals, relict-filled 

 stream channels, and outcrops of sandy coastal plain strata on the shelf 

 floor. Except for the shoals, these deposits rarely have topographic 

 expression and can be detected only by seismic reflection and core data. 



Frying Pan shoals off Cape Fear and Lookout shoals off Cape Lookout 

 are the main shoal deposits in the study area. Occasional shore-connected 

 linear shoals and shoals off the mouth of inlets are also potential 

 sources but of much smaller size. Relict stream channels can be detected 

 on the seismic reflection records throughout the area, particularly in 

 Onslow Bay. Cores from these channel areas indicate that most of them 

 south of New River Inlet do not contain quartz sand but are either filled 

 with or capped by biogenic calcareous sand, gravel, and rock. 



Most of the quartz sand occurring outside shoal areas is located in 

 the thin and discontinuous Holocene surficial layer and in outcropping 

 Coastal Plain strata associated with seismic reflection units I and III. 

 These deposits consist largely of types B and C sediment and together 

 with types A and D sand make up the larger part of accessible sand 

 reserves in the study area. All of these deposits are similar in 

 character, and in terms of distribution, accessibility, uniformity, and 

 freedom from objectionable matter would make excellent beach fill. How- 

 ever, the typical fine size range of most of types A, B, and C material 



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