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A composite Holocene sea-level curve for the northern Gulf of Mexico coastal region was constructed using basal or bayline peat and swash-zone deposits determined from careful facies analysis. Initial work involved an assessment of published sea-level datums for the region, which show wide scatter. Reevaluation of individual data points based on sea-level–specific criteria required exclusion of most of these data from the composite curve. Additionally, variations in the age of the radiocarbon reservoir across the region were determined, and site-specific corrections were applied to the sample ages, further increasing the accuracy of the final sea-level curve, which is used in our reconstruction of the evolution of the bays of the region in companion papers herein.

The refined regional sea-level curve indicates that site-to-site variations in relative sea-level rise across the coastal plain spanning central Texas to Alabama are minimal. The data indicate rapid and possibly episodic rise during the early Holocene, followed by slower and more continuous rise during the middle and late Holocene. In addition, the new composite regional curve unequivocally plots sea level from −10 to −3 m below present from 8000 cal B.P. to 4000 cal B.P., which precludes the occurrence of a middle Holocene highstand above present sea level in this region. Last, a comparison of our composite curve to Caribbean sea-level curves suggests that coastal subsidence within the study area over the past several thousand years has been minimal. A comparison of the late Holocene record of sea-level rise to satellite altimetry and tide-gauge records indicates that rates of rise have increased by an order of magnitude over the past century.

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