may have previously contributed a large amount of sediment to the coastal 

 zone. 



29. Consistent with this discussion, Pilkey et al. (1969) noted that 

 sedimentation on the outer shelf is presently very slow. Pilkey and Field 

 (1972) conclude that much of the modern beach sand along South Carolina 

 originates from onshore transport across the inner continental shelf. Carver 

 (1971) postulated that most modern beach sediment along the Georgia coast was 

 from reworked Pleistocene Silver Bluff sediments. These reworked sands inter- 

 mixed with fluvial input from the Santee River. Swift et al . (1972) suggest 

 deposition of ebb-tidal delta complexes on the inner shelf during Pleistocene 

 low sea level stands, and likewise deposition in estuaries which would have 

 been seaward of the present shoreline, provide the principal sediment source 

 for modern beaches. Pleistocene estuary, inlet, and barrier deposits form a 

 20- to 40-km-wide lens of sand (up to 30 m thick) along the inner continental 

 shelf of the South Atlantic coast. According to Swift et al. (1972), ero- 

 sional shoreface retreat during Holocene transgression has moved these sedi- 

 ments in a landward direction, assisting in construction of the modern 

 shoreline. 



30. Shelf topography. In addition to sediment supply, topography of 

 the inner continental shelf affects shoreline erosion and accretion. Wave 

 refraction over shelf topography creates zones of potential erosion and depo- 

 sition along the coastline. Wave refraction also influences direction of wave 

 approach to the shoreline and therefore can influence littoral drift. Wave 

 convergence or divergence because of refraction may be influential in shaping 

 a large portion of South Carolina's coastal morphology. For example, Fico 

 (1978) conducted a wave refraction analysis along selected portions of coast- 

 line within the study area. She concluded that long-term erosion on Bull and 

 Capers islands was due in part to concentration of wave energy along these 

 shorelines by refraction across the shelf. 



Present Geomorphology 



31. In describing the modern coastline geomorphology, many authors 

 (e.g., Brown 1977; Nummedal et al. 1977; Hubbard, Hayes, and Brown 1977) have 

 considered the study area as being transitional between the microtidal (less 

 than 1.5-m tidal range) coastline of North Carolina and the mesotidal coast of 



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