A COMPOSITE SEA-LEVEL CURVE FOR THE NORTHERN GULF OF MEXICO FOR THE LAST 20,000 YEARS

Composite sea-level curves for the northern Gulf of Mexico coastal region have been compiled based on all available radiocarbon data. The history extends from the Last Glacial Maximum (c. 20,000 abs yr BP) to the present. The data set includes more than 350 dated paleo-shoreline indicators, including evidence for sea-level highstands during the latter half of the Holocene. The purpose of the project was to create a comprehensive sea-level database, and also to identify erroneous data by use of three criteria. First, data sets were sought from regions of the Gulf of Mexico exhibiting tectonic stability, to enable the composite data set to represent near-eustatic conditions. Given its geologic stability throughout the Quaternary and its relatively low-energy coastal environments, the northern Gulf of Mexico might be expected to exhibit a near-eustatic sea-level history. It therefore offers a detailed record of global sea-level. The resulting data set compares favorably with a recent late Quaternary sea-level history from the Red Sea, a high-resolution index of global eustatic change. Second, a new statistical technique was developed for identifying outliers in sea-level data. Third, a moving average method was used to analyze the remaining data, which lessened variability but enabled longer-term trends to be observed. The resulting compilation of northern Gulf of Mexico sea-level data has significance beyond the Gulf region. In particular, the recurring evidence of mid- to late Holocene high-stands in the northern Gulf of Mexico may be one of the best global verifications of such events.