Interglacial beach ridge plains across the northern Gulf of Mexico

Abstract

During past Interglacial periods, global ocean volume increased as a result of the higher temperatures and the melting of ice sheets, consequently leading to a rise in global sea levels. However, on timescales ranging from years to a few decades, regional sea level variability deviates from the global pattern, due to a combination of vertical land movements (earth’s crust viscoelastic response to glacial and ice sheet melting, tectonics), thermohaline circulation, wind forcing and land water storage. Therefore, decoding the regional sea-level variability during Interglacial periods is crucial for advancing climate models’ precision, especially for vulnerable coastlines. Beach ridge plains are valuable fossil geological archives, offering significant potential for the analysis of sea-level fluctuations, climatic shifts and catastrophic events. The extraction of these information can be achieved through the measured elevation of the dune-beach contact and the beach berm, the analysis of the fossil beach ridge orientation, the geometry of the internal stratigraphy and by dating of the beach deposits using optically stimulated luminescence (OSL) signals from quartz. In this study, we present results from our fieldwork campaign in the northern Gulf of Mexico, where we utilized a GNSS RTK station to obtain centimeter-level precision in measuring the elevation of the beach ridge sets, originally detected through freely available LIDAR datasets. Concurrently, a Ground Penetrating Radar (GPR) was employed to determine the stratigraphy of the beach ridge plains. Both surveyed areas, Apalachicola and Pensacola, contain fossil beach ridge sets varying in elevation from +2.5m up to a maximum of +7.5-8m above mean sea level, detected in more inland locations. Recent studies suggest that during the Last Interglacial period sea level in the area reached up to ~5m. The exact timing of the formation of the more elevated inland beach ridges remains uncertain, as does the question of whether their present elevation is attributable to post-Last Interglacial vertical land movements. Through in-depth analysis of the data collected during the WARMCOASTS ERC project, we aim to unravel the formation processes of these beach ridges and trace their development and evolution over time.