outer shelf areas, which they believe are areas of winnowing. They 

 found that mica was concentrated in a narrow nearshore zone and on the 

 upper continental slope which they interpret as areas of deposition. 

 The nearshore deposits in Long and Onslow Bays contain 20 to 40 grains 

 of mica per 10,000 grains and mostly less than 10 grains per 10,000 

 elsewhere on the North Carolina shelf. 



Latemauer and Pilkey (1967) studied phosphorite grains in North 

 Carolina shelf sediments and found that Onslow Bay surface sediments 

 contained significantly more phosphorite (3 to more than 14 percent) 

 than the adjacent Long and Raleigh Bays. They believe that the higher 

 frequency of phosphorite in Onslow Bay sediments probably indicates 

 derivation from local shelf outcrops of phosphatic strata. 



In a general study by Milliman, Pilkey, and Ross (1972), glauconite 

 is shown to be less than 5 percent in the North Carolina shelf region. 

 Farther seaward on the Florida Hatteras slope, frequencies as high as 

 95 percent glauconite occur in the noncarbonate fraction. 



(2) ICONS Data . Surface sediments found in the ICONS cores 

 are shown in Figures 26, 27, and 28. Not enough samples were collected 

 to delineate the extent and limits of the various sediments occurring 

 on the surface of the inner shelf; however, some of the deposits appear 

 to be very extensive. Core data provide evidence that shows many places 

 where materials of radically different lithologic properties lie in close 

 proximity. This is partly due to the thin bedded and discontinuous 

 nature of the Quaternary and modern sediments which produce a pattern 

 of modern sediment patches alternating with outcrops of older Quaternary, 

 Tertiary, and Late Cretaceous sediments. Consequently, many of the sur- 

 face sediments are relict and not consistent with the hydraulic process 

 now dominating the inner shelf. 



The most striking feature of surficial sediment distribution in the 

 study area is the predominance of a fine sand facies in Long Bay and 

 Frying Pan shoals. This is in contrast to coarser sediments and pre- 

 Holocene outcrops which dominate the Onslow Bay inner shelf and suggests 

 that the sedimentation history as well as present inner shelf processes 

 in the two areas may be substantially different. Many of the coarser 

 sediments which occur on the shelf floor are probably relict deposits 

 of the last transgression or have been reworked from such deposits. 

 Because of the lower sea level at that time, streams likely delivered 

 coarser detrital sediments to the shelf than are presently available. 

 Other coarse surface deposits were also probably generated at this time 

 by reworking of substrate material as the shoreline advanced across the 

 present shelf floor. Evidence of this derivation is indicated by inver- 

 tebrate remains in surficial deposits that are clearly exotic in the 

 existing inner shelf environment but are contained in situ in the under- 

 lying relict substrate. The mineralogy also suggests reworking in many 

 places where calcareous particles, phosphorite, or glauconite from sub- 

 strate deposits appear in abundance in the overlying sediments. Reworked 

 substrate deposits have been described as a common mode of origin of shelf 



67 



