Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: Implications for the regional sediment budget and long-term shoreline response

TitleHolocene sediment distribution on the inner continental shelf of northeastern South Carolina: Implications for the regional sediment budget and long-term shoreline response
Publication TypeJournal Article
Year of Publication2013
AuthorsDenny JF, Schwab WC, Baldwin WE, Barnhardt WA, Gayes PT, Morton RA, Warner JC, Driscoll NW, Voulgaris G
JournalContinental Shelf Research
Volume56
Pagination56-70
Date Published2013/03
Type of ArticleArticle
ISBN Number0278-4343
Accession NumberWOS:000318582400005
Keywordsbudget; coastal erosion; geologic framework; grand strand; Holocene sediment; island; Long Bay; new-york; north-carolina; sand ridges; sediment; shoreface profile; South Carolina; united-states; west-central florida; wrightsville beach
Abstract

High-resolution geophysical and sediment sampling surveys were conducted offshore of the Grand Strand, South Carolina to define the shallow geologic framework of the inner shelf. Results are used to identify and map Holocene sediment deposits, infer sediment transport pathways, and discuss implications for the regional coastal sediment budget. The thickest deposits of Holocene sediment observed on the inner shelf form shoal complexes composed of moderately sorted fine sand, which are primarily located offshore of modern tidal inlets. These shoal deposits contain similar to 67 M m(3) of sediment, approximately 96% of Holocene sediment stored on the inner shelf. Due to the lack of any significant modern fluvial input of sand to the region, the Holocene deposits are likely derived from reworking of relict Pleistocene and older inner-shelf deposits during the Holocene marine transgression. The Holocene sediments are concentrated in the southern part of the study area, due to a combination of ancestral drainage patterns, a regional shift in sediment supply from the northeast to the southwest in the late Pleistocene, and proximity to modern inlet systems. Where sediment is limited, only small, low relief ridges have formed and Pleistocene and older deposits are exposed on the seafloor. The low-relief ridges are likely the result of a thin, mobile veneer of sediment being transported across an irregular, erosional surface formed during the last transgression. Sediment textural trends and seafloor morphology indicate a long-term net transport of sediment to the southwest. This is supported by oceanographic studies that suggest the long-term sediment transport direction is controlled by the frequency and intensity of storms that pass through the region, where low pressure systems yield net along-shore flow to the southwest and a weak onshore component. Current sediment budget estimates for the Grand Strand yield a deficit for the region. Volume calculations of Holocene deposits on the inner shelf suggest that there is sufficient sediment to balance the sediment budget and provide a source of sediment to the shoreline. Although the processes controlling cross-shelf sediment transport are not fully understood, in sediment-limited environments such as the Grand Strand, erosion of the inner shelf likely contributes significant sediment to the beach system. Published by Elsevier Ltd.

DOI10.1016/j.csr.2013.02.004
Short TitleCont Shelf Res
Integrated Research Themes: 
Student Publication: 
No