Developing Proxies for Late Holocene Sea-level and Climate Change along the Northeastern Gulf of Mexico Coast

Abstract

The goal of this investigation was to develop sea-level and climate proxies for the northeastern Gulf of Mexico during the late Holocene. The purpose was to help better understand the relationship between climate change and fluctuations in sea-level and storm frequency. The data sources were a ground-penetrating radar (GPR) transect across a barrier island beach ridge plain on the northwestern coast of Florida, and a sediment core from a coastal lake on the same barrier island. The study site was St. Vincent Island, a barrier island beach ridge plain. The GPR data have been used to develop a proxy for sea-level change, while the sediment core has been analyzed for proxy evidence of paleo-storm occurrence. The process by which the study was conducted was as follows: 1) determine sedimentation rates and sediment characteristics in a coastal sediment core using radiocarbon, lead-210 dating, and a new method with a laser particle analyzer; 2) use the chronology of known historic hurricanes to determine the signature of major storms in the historic portion of the sediment record; 3) employ the storm signature to create a paleo-storm proxy in the long-term sediment record; 4) process and utilize a new method to analyze field GPR data to determine past sea-levels, based on the depth of basal deposits of the ridges in a beach ridge succession; and 5) correlate the sea-level history and paleo-storm occurrences to the regional climate history based on published proxy studies. Both climate-related proxies were found to correlate with previous proxies developed for this region. The new method of determining paleo-sea level, through use of the GPR data, was successful at determining paleo-sea level.