3.9 KA SUPERSTORM FORMATION OF A COASTAL LAKE BASIN AND SUBSEQUENT HURRICANE AND CLIMATE CHANGE RECORD, ELEUTHERA, BAHAMAS

Coastal geomorphological modification due to a superstorm around 3.9 thousand years ago has been documented through an integrated dataset comprising ground-penetrating radar (GPR) and lake sediment core records on a carbonate platform. The superstorm led to the formation of a storm-emplaced barrier, isolating a lagoonal marine embayment on Eleuthera Island, The Bahamas, resulting in the creation of a hypersaline lake basin. Originally, the area was a coastal mangrove swamp before the installation of the barrier. The lake basin developed on antecedent topography, with Pleistocene headlands bounding the embayment. Geophysical imaging reveals that the barrier's origin was a singular event, likely an intense storm. GPR surveys depict a landward sloping surge barrier with a recent foredune, contrasting with multiple beach-ridge sets of paleoshorelines.

The recorded event falls within a global period of heightened storminess between 4100-3700 YBP, serving as a southern datapoint that complements Atlantic seaboard records. The preserved barrier suggests that its installation was followed by a sea-level stillstand after the postglacial transgression, aligning with regional and global sea level records.

Post-impoundment, the saline coastal pond preserves a finely detailed climate and hurricane record. These records indicate increased wetness in the Caribbean basin and Western Atlantic after 1300 YBP, with a relatively stable period in the Bahamas from 1300 YBP to approximately 300 YBP. Hurricane proxy indicators reveal heightened activity between 3900-2000 YBP, with additional spikes between 1100-1000 and 900-500 YBP, coinciding with the Medieval Climatic Optimum.