grains within Cretaceous and Tertiary deposits underlying the shelf floor 

 makes their worth as tracers questionable because potential sources of 

 phosphorite grains to the modem shelf sediments are nearly ubiquitous. 

 Latemauer and Pilkey (1967) suggested that the value of phosphorite 

 grains might be enhanced by considering grain color which they found to 

 vary from place to place. Variations in predominant color and shape 

 were also noted in localities sampled by the ICONS cores. Thus, a more 

 detailed sampling and study of phosphorite characteristics in potential 

 source beds might show that particular types of phosphorite grains could 

 be usefully used as natural tracers. 



Rock fragments from lithified Tertiary and Pleistocene outcrops are 

 also potential large-size tracer elements which indicate erosion and 

 transport conditions on the shelf. Rock fragments from Pleistocene 

 coquina outcrop on the sea floor near Cape Lookout are washed up on the 

 beaches on both sides of the cape (Mixon and Pilkey, 1976); calcareous 

 sandstones and fragments of Ostrea gigantissima Finch from nearshore 

 outcrops of probable Oligocene age occur on the beaches around New River 

 Inlet (Lawrence, 1975). 



Several faunal elements in the shelf floor and subfloor sediment 

 bodies are nearly unique to the unit and may prove useful as natural 

 tracers. Mo Husks are potentially the most useful, especially those 

 derived from the Tertiary and Cretaceous substrate deposits; most are 

 clearly exotic in more recent sediments. For example, the Cretaceous 

 shells found on the shores of Long Bay can be related to sea floor 

 exposures of Cretaceous sediment from which the shells are eroded and 

 subsequently transported to the beach (Cooke, 1936). Probably, there 

 are several molluskan species that can also be used to indicate erosion 

 and movement of material from the Tertiary deposits; however, the avail- 

 able core samples of these units contain too few megafossils to list 

 specific types. Occasional mollusk shells and fragments indicate they 

 exist but are probably not dense enough to be sampled often by the cores. 

 Larger samples from outcrops are needed to characterize the megafauna. 



Barnacle plates and opercular valves are abundant constituents of 

 the Pliocene calcareous sediment and rock (type G lithology) and in the 

 Miocene deposit at core 96 but sparse to rare elsewhere. Thus, the 

 presence of large quantities of barnacle parts in the modem sediments 

 may indicate transport or vertical mixing from the older deposits; how- 

 ever, the appearance of barnacle parts alone is not conclusive since 

 these organisms presently contribute to the shelf sediments in small 

 quantities. 



Similarly, the presence of large quantities of bryozoa in modern 

 shelf sediments suggests derivation from one of the two bryozoa-rich 

 deposits in the study area--the Plio-Pleistocene calcareous sediment and 

 rock (type G lithology) or the Eocene bryozoan hash outcropping in Long 

 Bay. 



Microfaunal elements, particularly the foraminifera, are usually 

 abundant in marine sediments and many are potentially usable for natural 



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