more often it is relatively free of fines. Phosphorite is a common 

 accessory and mollusk shell material is usually present. Foraminifera, 

 echinoids, and other small skeletal debris that commonly occur in finer 

 sediments are rare. 



Type D sand is light gray (10 yr 7/1) to light brownish gray (10 yr 

 6/2) and usually uniform: In some samples there is a speckling of darker 

 grains which consist mostly of colored shell fragments and phosphorite. 



(2) Type E . Type E sediment includes all coarse deposits in 

 which shells and shell fragments make up about 30 percent or more of the 

 material, thus giving it a distinct texture and composition. It is a 

 broadly defined category with lithologies ranging from shell sand to 

 shell gravel (Fig. 20). These sediments occur throughout the study area, 

 usually in thin discontinuous patches on the shelf floor or in shallow 

 subfloor deposits. Subsurface deposits are commonly silty with a detri- 

 tal fraction of poorly sorted, fine to coarse quartz sand. Surficial 

 exposures and deposits are not as silty and tend to have a coarser 

 detrital fraction, probably because of reworking. 



The shell material in type E is predominantly derived from mollusks, 

 barnacles, bryozoa, serpulid worms, and echinoids; foraminifera are common 

 to abundant, and small pieces of coral and calcareous algae occasionally 

 occur. In most places the shells are a mixture of old shells that are 

 highly worn, pitted and encrusted, and fresh unaltered shell material. 

 The worn shells are often blackened or iron-stained. Fragments with 

 broken edges are smoothed by wear. In many cases, these shells are 

 detrital or reworked elements derived from older deposits; the fresh 

 shells are locally produced. 



Most of the type E material is gray to grayish brown or brown and 

 rarely uniform, consisting of a varicolored pattern of cream, gray, black, 

 and brown individual shell fragments and gray or brown matrix material. 

 Several of the shell sands and gravels occurring on the shelf floor are 

 heavily iron-stained which gives them a more uniform reddish-brown color. 



c. Silt and Clay . Deposits of silt and clay size particles occur 

 throughout the study area but are particularly common in Long Bay. These 

 deposits are neither as extensive nor numerous as the sand deposits and 

 usually occur in the thin and discontinuous layer overlying the major 

 reflection units. In general, they cannot be identified or traced on 

 available seismic reflection units. 



The most common fine-grained deposits consist of highly plastic, dark 

 to very dark gray clay (type F) . Other fine-grained deposits are heter- 

 ogeneous and are mostly mixtures of various amounts of sand, silt, and 

 clay. The deposits appear to be unrelated and probably represent a 

 variety of depositional situations. Their characteristics are individu- 

 ally noted in the core logs (App. B) . 



Type F, a distinctive dark-gray clay with yellow mottling, occurs 

 in many cores from Long Bay and in a few cores from Onslow Bay. The 



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