Section V. SUMMARY 



Between Palm Beach (26°48'N) and Cape Kennedy (28°27'N) the south- 

 eastern Florida Coast is bordered by a submerged plain extending to the 

 top of the Florida-Hatteras slope. The top of the slope occurs at about 

 -80 feet MLW and 2 miles offshore near Palm Beach, and at about -230 

 feet MLW, 38 miles offshore at its widest point south of Cape Kennedy. 



Based on coastal well logs and seismic reflection records, strata 

 underlying the submerged plain to -500 feet MLW are judged to range from 

 Eocene to Holocene in age. These strata all dip generally eastward, but 

 below a presumed unconformity ranging in depth from about -140 to -220 

 feet MLW, strata dip southeastward and the rate of dip is nearly doubled. 



The surface of the Shelf plain is topographically divisible into 

 a narrow sloping shore face, inner and outer Shelf zones and the Shelf 

 marginal zone. The Shelf margin and outer Shelf have irregular surface 

 topography and many indications of "rocky" bottom. The inner shelf is 

 mostly mantled by unconsolidated sediments forming many shoal ridges and 

 hills interspersed with relatively flat areas. The shoreface consists 

 mainly of a sloping sedimentary apron connecting the Shelf plain and the 

 littoral zone. 



Shallow subbottom strata beneath the Shelf surface appear on siesmic 

 profiles as thinly bedded and generally parallel to one another. Internal 

 bedding features are common and usually consist of high and low angle sea- 

 ward dipping bedding planes. The uppermost continuous reflector dips from 

 about -40 feet MLW under the shoreface to apparent outcrop around -65 feet. 

 Cores penetrating to the reflector level indicate that it is composed of 

 variable carbonate sediments with locally lithified layers. This unit is 

 tentatively dated as pre- late Wisconsin. 



Sediments above the upper continuous and regional reflector reach 

 a maximum thickness of 30 feet under shoals, and thin to as little as 

 1 foot over flats and swales between shoals. In limited areas on the 

 inner Shelf (i.e., -40 to -70 feet MLW) and in most places on the outer 

 Shelf (-70 feet MLW to Shelf edge), there is no sediment cover over the 

 continuous reflector. The sediment mantle of the inner Shelf consists 

 primarily of sand, silty sand, and shell gravel. Main constituents of 

 this sand are calcium carbonate skeletal fragments; ooids and quartz are 

 the most important secondary constituents. 



Sediment on beaches adjacent to the study area consists of quartzose 

 sand and shell fragments, the latter generally broken, well-rounded and 

 polished. Median size of midtide samples generally lies in the 0.3 to 

 0.5 mm (1.74 to 1 phi) range. 



Surficial sediments in the Fort Pierce grid area between the 40 and 

 60- foot water depth contours consist primarily of coarse, brown shell 

 sand forming an irregular blanket deposit varying in thickness from 



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