7. Regional Marine Geology. 



The name East Coast Shelf was proposed by Uchupi (1968) for the gently 

 seaward-sloping submarine plain bordering the Altantic coast from near Cape Cod to the 

 Florida Keys. The north Florida Atlantic shelf area is part of the southeastern shelf. This 

 shelf has been widely studied and therefore the geology is well known relative to other 

 shelves of the world (Emery, 1969). Age and lithology of the sediment cover, as well as 

 physiography and subsurface structure have been reported by numerous investigators. 

 Discussions of regional aspects of the Atlantic shelf marine geology have been presented by 

 Tyler (1934), Stetson (1938), Gorsline (1963), Curray (1965), Emery (1965), Pilkey 

 (1968), Uchupi (1968, 1970), Pilkey, et al. (1969), Maclntyre and Milliman (1970), Duane, 

 et al. (1972), MilHman, Pilkey, and Ross (1972), Pilkey and Field (1972), and Swift, et al. 

 (1972). While such studies provide useful background material, their direct application to 

 the objectives of this report are limited because of sampling methods (surface grab), sample 

 low density, and area of study, which usually include deeper parts of the central and outer 

 shelf. 



These studies have shown that the shelf is comprised of gently dipping Tertiary strata 

 with a thin overlying layer of Quaternary deposits that has been deposited in response to 

 Pleistocene sea level fluctuations. Terraces and ledges mark tlie site of former sea level 

 positions, and topographic highs or shoals are common features which some believe 

 originally formed along the slioreface and are now in a quasi-equilibrium stage. Surface 

 sediments likewise are in a tjuasi-equihbrium stage, in that their textural character indicates 

 equiUbrium with the wave conditions but their composition suggests in place reworking of 

 older relict deposits. A vast majority of shelf surface sediments has been derived from the 

 complex raetamorphic Piedmont Province; streams draining the Piedmont are far more 

 significant tlian streams draining Coastal Plain regions in terms of sediment quantities to the 

 shelf. Locally on the slielf, biogenic (shell material) and residual (Tertiary surface exposures) 

 sediments are abundant. 



II. GEOMORPHOLOGY AND SHALLOW SUBBOTTOM STRUCTURE 

 OF THE CONTINENTAL SHELF 

 1. Continental Shelf Geomorphology. 



a. General. The East Coast Shelf in tlie study area (Fig. 6) is transitional between the 

 narrow, topographically irregular shelf characterizing the region at, and south of Canaveral 

 Peninsula and the broad, topographically subdued shelf typical off most of the southeastern 

 United States. 



For descriptive purposes the Atlantic shelf off northern Florida can be divided into three 

 major geomorphic units: slioreface, shelf floor, and shelf edge (Fig. 7). These units, based on 

 the primary subdivisions of Price's (1954) idealized shelf equihbrium profile, are used here 

 in a strictly geomorphic sense witliout implication as to genesis or equilibrium state of the 

 units. 



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