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Abstract

High-resolution seismic data suggest that portions of depositional sequences representing as many as 18 Quaternary sea-level highstands are preserved within 60 m of Quaternary deposits in northeastern North Carolina. Sediments deposited during at least seven of these Quaternary sea-level events have been defined within the upper 33 m in drill holes in Dare County. The complex stratigraphy was resolvable only after integrating detailed lifho-, bio- and aminostratigraphic drillhole data with a high-resolution seismic framework.

High-frequency, sea-level cyclicity dominated the depositional patterns of the resulting Quaternary sediment sequences. As high-energy coastal systems moved repeatedly across the low-gradient continental shelf, sediment units that had previously been deposited in coastal and shelf environments were significantly modified. During each glacial episode, fluvial channels extensively dissected previously deposited coastal facies. Subsequent deglaciation and transgression flooded the channels, backfilling them with fluvial and estuarine sediments. The infilled channel facies were then partially truncated by shoreface erosion, which also eroded portions of previously deposited coastal sequences. During sea-level highstands, a new sequence of coastal facies was deposited over the ravinement surface cut into remnants of older and similar Quaternary sequences and the associated channel-fill systems. Thus, the resulting record consists of a series of imbricated coastal deposits of similar, but discontinuous, lithostratigraphic units with irregular geometries that only partially represent interglacial highstand deposition; the depositional sequences are highly punctuated and dominated by unconformity surfaces with extensive incised and backfilled channel deposits.

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