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Abstract

The elemental compositions of relatively unweathered Fe-Ti oxide grains, mostly ilmenite, separated from 83 samples collected from late Pleistocene to modern beach sands in Virginia and North Carolina were compared to those of 72 samples from five potential source rivers, the Roanoke, James, Potomac, Susquehanna, and Hudson Rivers. The composition of the Fe-Ti oxides from the toe of the Suffolk Scarp have a much different provenance than do younger beach deposits to the east. Based on discriminant analysis classification of the Fe-Ti oxide compositions with potential source rivers, the Suffolk Scarp beach is inferred to have been derived primarily from the James River; the younger beaches, including modern beach deposits of the Outer Banks, North Carolina, are inferred to have been primarily from the Susquehanna River with minor input by the Hudson River via longshore transport and reworking of shelf sands. The difference in provenance is due primarily to the origin of the Suffolk Scarp beach by erosion of older estuarine units in a protected-bay beach setting, whereas the younger beach deposits were derived from reworking of shelf sands, probably bay-mouth sand deposits (massifs), in an unprotected or barrier-beach setting. Subtle differences in the Fe-Ti oxide compositions among beach deposits are due to changes in the mix from the different river sources. Discrimination of the differences allows for a clearer understanding of the interrelation among those coastal-plain ridges and scarps that contain the beach sands.

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