Certain aspects of the sediment mineralogy point to a modern depositionaJ origin of 

 type F sand. The sands contain little or no phosphorite, and are micaceous like the Georgia 

 counterpart shoreface sands. The mica content reflects fluvial derivation since both offshore 

 surface sands and subsurface deposits are deficient in this mineral. 



Faunal assemblages remain constant throughout shoreface cores indicating continuity of 

 the deposit. The Elphidium-Ammonia foraminiferal assemblage indicates an environment 

 with fluctuating temperature, salinity, and turbidity. Although most commonly associated 

 with marginal marine estuaries, lagoons, and semi-enclosed bays, these conditions may also 

 occur in nearshore water off open coasts and where few or no streams discharge in the 

 coastal area. Kohout and KoHpinski (1967) have shown zonation of organisms in Biscayne 

 Bay, Florida, due solely to ground water percolation through the bottom. 



Macrofauna of the shoreface are chiefly echinoids and the pelecypods Mu/mia, Anadara, 

 and Corbula, none of which is restricted to a narrow well defined environment (Abbot, 

 1954; Stanley, 1970). Shells are evenly dispersed throughout the shoreface; shell gravels or 

 hashes were not in any of the cores examined. 

 3. Origin of Area Beach Sediments. 



Areal beach sediments range in size from coarse to fine sand and contain between 2 and 

 95 percent acid soluble material. These variations in grain size and shell content of beaches 

 between Cape Canaveral and Fernandina result from coastline orientation and exposure, 

 availability of offshore source materials, and local presence of Pleistocene coquina outcrops. 

 Additionally, short-term changes in sediment cliaracter are induced by intense periodic 

 storms, tidal fluctuations, and seasonal changes in wave direction. 



Location, percent acid soluble material, mean grain size, and sorting are plotted for each 

 of 32 beach samples siiown in Figure 37. Eacii location represents a single sample collected 

 from the swash zone at a specific time; values shown in tlie figure are not long-term 

 averages. Results shown on the chart are representative of subtle regional trends and overall 

 variation in characteristics of areal beach sands. 



Curves for mean sand size and shell content are directly related— nearly every increase in 

 shell content is paralleled by an increase in grain size. This pattern indicates that mean sand 

 size is primarily a function of composition, and this correlation is further reflected by the 

 sorting curve (Fig. 37). Although the sorting curve does not always parallel the other two, 

 decreases in grain size and shell content are frequently marked by a decrease in the standard 

 deviation, indicating better sorting. Such a pattern further demonstrates the influence of 

 shell material in the areal beach sediments— sands containing lesser amounts of shell material 

 are finer and appear to be better sorted than those enriched in biogenic sand. Mollusks, 

 cliiefly pelecypods, are the primary contributors of carbonate material, whether derived 

 from recently living fauna or reworked Pleistocene deposits. Whelks, conchs, and other 

 gastropods also contribute a significant amount of shell to beaches. Among the minor 

 components of the carbonate assemblage, the absence of ooids is of particular note. Ooids 



77 



