relationships. Certain generalizations can be stated with regard to age and origin of each 

 type. Type E is a partially lithified Pleistocene calcarenite that in some areas is the source 

 rock for overlying units. Poorly sorted overlying sediments (Type C) are relict from a 

 Holocene lower sea level. Surficial layers of mud in Canaveral Bight and lenses of very fine 

 sand at the bases of Chester and Southeast Shoals arc judged to be redistributed modern 

 deposits (Type H) as are the medium and coarse sands (Type A) which blanket the inner 

 shelf in sheet and shoal deposits. 



b. Semiconsolidated Sediments (Type E). Three Hnes of evidence indicate that Type E 

 material is derived from the geologic strata generating the continuous and mappable seismic 

 reflection of the blue horizon. First, the Uthologic difference between Type E and overlying 

 sediment types is marked, particularly the occasional appearance of an intergranular cement 

 that is likely to produce a widespread acoustic contrast sucli as depicted by the blue 

 horizon. Second, there is a correlation between location of cores containing Type E material 

 and areas of thin overburden (all 20 feet and most 10 feet). Third, strata associated with tiie 

 blue horizon seem to crop out or he near the surface at the outer edge of the grid, described 

 earlier by Moe (1963) as an uneven bottom with numerous rock ledges and terraces over 

 6-foot relief. 



Type E sediment is chiefly skeletal fragments and quartz; the fauna is similar to that of 

 other sediment types of the grid area, such as the abundance of Mercenaria campechensis 

 and Chione chancellata. Both pelecypods indicate clean or slightly muddy sand substrata in 

 an intertidal or subtidal environment. (Stanley, 1970.) Donax variabilis shells in core 144 at 

 —6 feet subbottom depth corresponds to the position of the blue horizon; Donax inhabit 

 the intertidal zone and are excellent indicators of shoreline position. (Abbott, 1968), 

 (Stanley, 1970.) Less than 5 percent of calcareous oolitic grains (ooids) are in rock 

 fragments and unconsolidated sands of Type E material. Formation of ooids usually occurs 

 in a warm, saline, agitated water, by concentric deposition of calcium carbonate around 

 detrital skeletal and terrigenous grains, and are good indicators of an original shallow water 

 environment. (Monaghan and Lytle, 1965), (Newell, Purdy and Imbrie, 1960), (Ginsburg, et 

 al., 1963.) These lines of evidence suggest that Type E sediments were deposited in a 

 shallow marine environment and later partially lithified under subaerial conditions. 



c. Relict Holocene Sediments. Type C sediment, judged a reUct deposit, is present 

 throughout the grid in variable thicknesses, usually less than 3 feet. Occasionally the 

 sediment is exposed at the surface, mostly in the shallow depressions near the shoals. The 

 sediment is nearly ubiquitous, but its characteristics vary and its distribution lacks 

 continuity. 



The wide variation in grain size of Type C sediments due to the mixture of terrigenous silt 

 and sand and calcareous sand and gravel, and the faunal assemblage, is indicative of the 

 origin of the material. Poor sorting suggests a low energy environment where sediments 

 accumulate by a variety of slow processes, such as a lagoon or lee side of a barrier. Principal 

 fauna are representative of protected waters. Crepidula fornicata, Anadara sp. are moUusks 

 which typically inhabit a quiet marine environment. (Bernard, Le Blanc, and Major, 1962), 

 (Stanley, 1970.) Ooids are occasionally in Type C sediment, and their presence suggests that 

 some sand-size Type C sediment is from bottom erosion of the underlying blue layer 

 (Type E sediments). The fauna of the blue layer and the evidence of coquina exposures in 

 this area, suggests that some shells associated with Type C sediment are not indigenous 

 fauna. 



47 



