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Morphology and textures of modern sediments on the inner shelf of South Carolina's Long Bay from Little River Inlet to Winyah Bay

May 19, 2007

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.

Citation Information

Publication Year 2007
Title Morphology and textures of modern sediments on the inner shelf of South Carolina's Long Bay from Little River Inlet to Winyah Bay
DOI 10.3133/ofr20051345
Authors J. F. Denny, W. E. Baldwin, W. C. Schwab, P. T. Gayes, R. Morton, N. W. Driscoll
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 2005-1345
Index ID ofr20051345
Record Source USGS Publications Warehouse
USGS Organization Coastal and Marine Geology Program