Abstract

Three distinct types of quartz grains were found to dominate different portions of Holocene/Pleistocene cores from both Pawleys Island and Kiawah Island, South Carolina. In the Pawleys Island core, the Pleistocene section is dominated by Appalachian Piedmont-derived grains that are irregular in shape with inherited facets and deep indentations. The lower Holocene portion is characterized by grains that are smoother in outline and silica-plastered. The uppermost Holocene sands are typified by smooth, rounded and abraded, silica-plastered quartz grains. This sequence is due to changes in provenance. The ancestral Pleistocene Pee Dee Rivers flowed into the Atlantic in the Myrtle Beach area and delivered Piedmont grains to the Pawleys Island area. Southward diversion of this river system cut off this source, leaving as a source sand delivered from coastal-plain sediments brought in by longshore drift. Vertical changes in sand shape from the Pleistocene/Holocene cores from Kiawah Island are an effect of changing provenance inasmuch as all grains showed unabraded surfaces. The studies of these two areas with distinctively different histories show significant changes in quartz shape through time. This suggests that a provenance stratigraphy based on grain shape can be established which may help in unravelling littoral-accumulation history.

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