Abstract

The heavy mineral suites of continental shelf sediments off the coast of South Carolina in the area of 32 degrees 30'N latitude, 79 degrees 50'W longitude, and of sediments from James Island, South Carolina, are dominated by epidote, hornblende, and opaque minerals (ilmenite, hematite, magnetite, phosphorite); and significant amounts of garnet (almandite), sillimanite, staurolite, tourmaline (schorlite), actinolite, and kyanite are present. This suite of minerals has been ultimately derived from metamorphic rocks of the Piedmont Province, but at least a part of the suite has resided temporarily in Coastal Plain sediments. Rounded, polished phosporite nodules present in the opaque group have been derived from existing shore deposits, although the ultimate source is believed to be Miocene sediments. No evidence was found to indicate a contribution from existing continental shelf sediments. The light mineral fraction (specific gravity less than 2.8) is composed mainly of quartz and carbonate detritus (greater than 95 percent), and includes about 5 percent potash feldspars and plagioclase feldspars. Clay size fractions composed of kaolinite, illite, and montmorillonite were present in quantities less than one percent in the shore (James Island) and nearshore samples. No clay minerals were found in offshore samples; this is attributed to the "scrubbing" action of the marine currents reported to be active in the area.

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