Millennial Scale Development of a Southeastern United States Spit

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Coastal spit, ground-penetrating radar, North Island, optically stimulated luminescence, South Carolina

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A prominent 4-km-long and 1-km-wide spit is located at the southern downdrift end of the Grand Strand coastline in NE South Carolina. To reconstruct a millennial scale record of spit evolution, an integrated suite of data collection was employed, including LiDAR data, ground-penetrating radar data ground truthed by vibracore and split-spoon auger data, and optically stimulated luminescence (OSL) ages. OSL ages suggest initial spit formation began around CE 1100. During the last millennium, the spit records four periods of major advance: three by OSL ages around CE 1105 to 1240, CE 1485 to 1600, CE 1725 to 1835 and one by historical records after CE 1872 until prior to CE 1980. Each section grew by southerly advance of the spit platform, revealed by dipping foreset reflectors, overlain by beach, overwash, and eolian units. Section boundaries are indicated by abrupt OSL age differences, larger ridges (>4.5 m), and, for the middle spit sections, wide downdrift platforms. Episodic growth of the spit may be related to ebb-tidal channel switching, with channel migration establishing platform development or changes in updrift sediment supply. For the central zones, lack of shoreline advance across the downdrift platform suggests a changing sediment supply. The formation of the north and north-central section and associated recurved ridges correspond with times of heightened hurricane activity in the Western North Atlantic, whereas ridges in the south section appear to be related to local hurricane and storm activity. The north-central section had a particularly rapid advance, which is attributed to increased sediment supply. The most recent advance of the spit was also influenced by jetty construction between CE 1890 and 1905. In comparison to the greater amount of research that has been done on longer term coastal geologic evolution and decadal-term shoreline change, intermediate centennial-scale variations were formerly more difficult to age date and study. Determining coastal change on intermediate time scale, however, is important for understanding coastal systems such as the Grand Strand.

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Citation / Publisher Attribution

Journal of Coastal Research, v. 34, issue 2, p. 255-271