predominantly quartz with a small percentage (< 10) of shell fragments, residual 

 phosphorite and accessory detrital minerals, and is commonly less than 10 feet thick. 

 Beneath the surficial deposits, and locally exposed at the surface are Pleistocene shelly 

 quartz sand and Tertiary foraminiferal-rich quartz sands, and dolomitic quartz sands. 



Biogenic particles generally comprise less tlian 20 percent in most sediments of the study 

 area. The main biogenic entities are mollusk shells, echinoid parts, foraminifera and 

 ostracods. Analyses of macrofauna and microfauna indicate that lithologically defined 

 sediment groups are genetically related. 



Tertiary sediments bear a microfaunal assemblage indicative of deposition in water 

 much deeper than presently exists in the study area. The terrigenous fraction was probably 

 derived from the southeastern U.S. Piedmont province. Pleistocene deposits are very thin 

 and in most places absent from the shallow subbottom sediment column, indicating this 

 region was starved of sediment influx during repeated transgression and regression of the 

 sea. Evidence from cores indicates that a significant fraction of the inner shelf surficial 

 deposits may have been generated by erosion and reworking of the Tertiary substrate with 

 additional contribution of contemporaneous biogenic material. This evidence consists of the 

 thin nature of the Holocene overburden and the upward decrease in abundance and increase 

 in degradation of diagnostic grains (foraminifer, dolomite) across the Tertiary-Quaternary 

 boundary. 



Shoreface and beach sands are judged to be modern active deposits. Since few streams 

 discharge on the north Florida Atlantic coast, beach and nearshore sands are most likely 

 derived from shore erosion and Httoral transport of fluvial sand southward from sources 

 along the Georgia coast. 



During the next 50 years, 4.78 X 10^ cubic yards of suitable sand will be needed for 

 restoration and periodic nourishment of beaches along the north Florida Atlantic coast. 

 Favorable conditions exist for obtaining much of this supply from the inner shelf area. 



The best sources of sand for beach fill are the fine to coarse quartz sands in the Holocene 

 deposits of the shelf floor area. Tliick deposits of this sand, well suited for borrow, are 

 located in several places within the study area; however, not all sites are located near the 

 shorehne. Sediments from areas designated as suitable sites for beach restoration have an 

 average mean grain size of 0.30 millimeters (1.73 phi) and 95 percent of the samples have a 

 mean diameter between 0.50 and 0.177 millimeters (1 and 2.5 phi). 



99 



