Morphology and Texture of Modern Sediments on the Inner Shelf of South Carolina‘s Long Bay from Little River Inlet to Winyah Bay

Denny, J. F.; Baldwin, W. E.; Schwab, W. C.; Gayes, P. T.; Morton, R.; Driscoll, N. W.

Abstract:

High-resolution sea-floor mapping techniques, including sidecan-sonar, seismic-reflection, swath bathymetric systems, and bottom sampling, were used to map the geologic framework offshore of the northern South Carolina coast in order to provide a better understanding of the physical processes controlling coastal erosion and shoreline change. Four general sea floor environments were identified through analysis of sidescan-sonar, swath bathymetry, and surface sediment texture: inlet shoal complexes, shore-detached shoals, hardground, and mixed zones. Inlet shoal complexes generally lie offshore of modern inlet systems, with the exception of a shore-detached shoal lying offshore of Myrtle Beach. The shoals show 1 - 3 m in relief and comprise the largest accumulations of modern sediment within the inner shelf survey area. Surficial sediments within the shoal complexes are characterized by a low-backscatter, moderately sorted fine sand. Hardground areas are characterized by exposures of Cretaceous and Tertiary strata and Pleistocene channel-fill deposits. These areas display little to no bathymetric relief and are characterized by high-backscatter, coarser grained sand. Mixed zones show small-scale spatial variations in bathymetry, surface texture and backscatter. These areas are characterized by a thin layer of modern sediment (< 1 m) and exposures of Cretaceous strata and Pleistocene channel-fill deposits. Textural and geomorphic variations suggest a long-term net southerly flow within the study area. The general acoustic and textural character of the inner shelf within Long Bay suggests long-term erosion, reworking and continued modification of inner-shelf deposits by modern nearshore processes.

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USGS Numbered Series

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79962

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Denny, J. F.; Baldwin, W. E.; Schwab, W. C.; Gayes, P. T.; Morton, R.; Driscoll, N. W.

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USGS Woods Hole Science Center

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ENGLISH

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Available on DVD-ROM and online

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Geological Survey (U.S.)

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Open-File Report

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OFR

Citation Series Number:

2005-1345

Citation Search Results Text:

Morphology and Texture of Modern Sediments on the Inner Shelf of South Carolina‘s Long Bay from Little River Inlet to Winyah Bay; 2007; OFR; 2005-1345; Denny, J. F.; Baldwin, W. E.; Schwab, W. C.; Gayes, P. T.; Morton, R.; Driscoll, N. W.