Mica occurs only rarely and is common in only a few places where 

 cores contain micaceous silty clays unrelated to any of the principal 

 sediment types. Doyle, Cleary, and Pilkey (1968) showed that in surfi- 

 cial shelf sediments of the region mica is most common in nearshore 

 sediments at less than 15-meter (49 feet) water depth. They inferred 

 from the frequency distribution that the shelf floor sediments deeper 

 than 15 meters are probably being winnowed of mica which is carried 

 either shoreward to enrich the nearshore sediments or seaward to the 

 continental slope. 



Biogenic calcareous particles in sediments are dominated by mollusk 

 shells and shell fragments, echinoid spines, and test fragments (Fig. 15, 

 e and g) ; foraminifera are also widely distributed, but are abundant only 

 in fine sand and silt facies (Fig. 15, h). Calcareous algae, bryozoa, 

 ostracods, and barnacles are important in certain sediment bodies but 

 rare or missing elsewhere (Fig. 15,f,i,j,k). A substantial number of 

 small calcium carbonate particles seen in the grain counts were too small 

 to classify. Most of the particles are presumed to be small fragments of 

 the more abundant skeletal remains in the deposit. Siliceous skeletal 

 materials such as diatoms, radiolarians, and sponge spicules were rarely 

 found and do not constitute any significant part of the sediment deposits. 



Authogenic calcium carbonate grains in the form of oolites have been 

 reported in the surficial sediments of the Atlantic shelf and off both 

 Long and Onslow Bays (Terlecky, 1967; Milliman, Pilkey, and Blackwelder, 

 1968; Pilkey, et al., 1969; Milliman, 1972; Mixon and Pilkey, 1976). 

 The main concentrations with frequencies of more than 25 percent are in 

 mid and outer shelf locales where dated oolites indicate deposition during 

 the last recession of the sea (late Wisconsin). No oolites were identi- 

 fied in the ICONS samples; however, only a few cores were obtained from 

 the northern third of Onslow Bay where the oolite-bearing sediments extend 

 farthest shoreward. 



3. Sediment Categories . 



a. Fine Quartz Sand . Well-sorted, fine-grained quartz sand is the 

 most common sediment of the Cape Fear inner shelf region. Extensive areas 

 of the shoreface and inner shelf floor are mantled by this sand and large 

 deposits of similar material underlie much of the shelf floor. 



Most of the fine sands of the study area appear to be part of three 

 large deposits, each of a different age. As a result of varied history 

 and origin, these deposits are different in minor compositional elements, 

 fauna, and bulk properties. Though subtle in some respects, the dif- 

 ferences are significant in terms of engineering properties and are of 

 considerable importance in the development of regional stratigraphic re- 

 lationships. For convenience in notation, the three fine sand facies 

 will be referred to as sediment types A, B, and C. 



(1) Type A . Type A sand comprises the fine Holocene surficial 

 deposits which mantle large areas of the shoreface and inner shelf and 



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