294 Geologic Mapping (Posters)

Showcase your latest geologic mapping methods, techniques, and map products! This poster session highlights new detailed geologic maps addressing critical minerals, land management, groundwater, coastal resources, geologic hazards, and other derivative maps. NCGMP map submissions are encouraged.

Wednesday, 22 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

The Long Bay Cooperative Project: Using Lithostratigraphy to Inform Mapping and Stratigraphic Interpretations on the Continental Shelf

Paper number: 294-4
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Mapping the surficial and shallow stratigraphic distribution of sand, gravel, and minerals on the US continental shelf is important for economics, engineering, and multi-use conflict mitigation related to needs ranging from marine engineering to sand for beach nourishment. Ongoing collaborative work by the Bureau of Ocean Energy Management (BOEM), South Carolina Department of Natural Resources (SCDNR—Geological Survey), and project partners Coastal Carolina University (CCU), University of South Carolina (USC), United States Geological Survey (USGS), and University of Delaware illustrates the multi-disciplinary approach required to understand the lithology, physical characteristics, and distribution of offshore stratigraphic units. The Long Bay Cooperative Study (SC COOP) aims to refine the geologic framework of Long Bay, located offshore of Brunswick County (southern North Carolina) and Georgetown and Horry Counties (northern South Carolina). The goal is to identify zones of potential sand, gravel, and mineral resources (REE including monazite as well as zircon, apatite, rutile, and ilmenite) using spatial and temporal relationships and to develop sand-search strategies built on these findings.

An overview of this multi-year project will focus on the lithostratigraphy of 38 vibracores collected in Long Bay (approximately 5-12 nautical miles from shore) by BOEM contractor APTIM in 2015 and 2022. Lithologic logging identified siliclastic and calciclastic sand, shell, calcium carbonate-cemented sand, phosphorite, and clayey silt with organic material (including wood fragments). Surficial deposits are interpreted as Quaternary and subsurface strata are likely Cretaceous (Peedee Formation), Paleocene (Williamsburg Formation), and Pliocene (Goose Creek Limestone). Stratigraphic information provides context for USC to ascertain the geotechnical character of the sediment, for CCU to connect onshore and offshore stratigraphy, and for the USGS for biostratigraphy. Geochronological estimates and mineralogical data (quantitative mineralogy as well as XRF) are included to provide provenance, age control-both laterally and downslope, and to identify zones of potential mixing of sediment and shell. Potential correlation with onshore stratigraphic units identified in borehole logs and outcrops is included, where applicable, and will aid in producing paleoenvironmental and paleoecological interpretations.

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

doi: 10.1130/abs/2025AM-414025

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