183-12 Preliminary Results of Grain Size and Biostratigraphic Analysis of Shallow Offshore Sediments from North and South Carolina’s Long Bay Region

Session: Recent Advances and New Voices in Marine and Coastal Geoscience (Posters)

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Abstract:

Long Bay is a coastal bay located offshore of Brunswick County, North Carolina and Horry and Georgetown Counties, South Carolina. It has been identified by the Bureau of Ocean Energy Management (BOEM) as a region suitable for offshore renewable energy development, and a region of high demand for mineral resources. In recent years, the Long Bay region has experienced a scarcity of beach quality sediment; factors such as low sediment supply, oceanographic processes, and low accommodation impact resource availability. Refining the Long Bay area geologic and sedimentologic framework will assist in the identification of zones containing sand and gravel deposits suitable for beach replenishment and highlight zones of interest for heavy mineral sand potential.

A set of 32 shallow (< 5 m) cores was acquired by BOEM in 2022 and subsequently sampled by federal, state, and academic collaborators in 2024. Preliminary grain-size analysis of samples from cores 33, 35, 40, 44, 47, 57, and 60 were compared to a matching sample set analyzed for calcareous nannofossil and diatom biostratigraphy. Grain-size data were obtained via a Beckman Coulter laser diffraction analyzer and classified using the Wentworth grain-size scale. Sediments are dominated by medium to coarse quartz sand with typically <25% clay.

Preliminary biostratigraphic analysis of samples from these seven cores documents the presence of Cretaceous (late Maastrichtian), Paleocene, and Quaternary sediments. These data will be used to provide a temporal and spatial framework across the region that allows for the correlation of sand bodies in onshore to offshore transects and laterally across Long Bay. This framework will help elucidate the character and distribution of these shelfal deposits and is being used to identify where sand and silt bodies of different ages (e.g. Cretaceous, Quaternary) overlap and pinch out. In the future, these data will be used in the production of a geologic map of the Long Bay region that uses integrated onshore to offshore data.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-11343

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