A 6000 YEAR MULTI-PROXY PALEOCLIMATE RECORD FROM A COASTAL POND AND BLUE HOLE ON THE ISLAND OF ELEUTHERA, BAHAMAS

High resolution paleoclimate records for the past 6,000 years have been recovered from 2 lakes of differing types—a coastal lagoon and a blue hole—on the island of Eleuthera, Bahamas. Multi-proxy records were analyzed on sediment cores from three sites (254, 114 and 104 cm in length) taken along shore-normal transects in Shad Pond, a hypersaline coastal lagoon and three sites (170, 155 and 151cm in length) from Duck Pond Blue Hole (DPBH). Sediment composition and granulometry, loss on ignition (LOI), X-ray fluorescence (XRF) measurements, as well as oxygen isotope and trace element measurements on ostracodes provide the basis for our reconstruction of the paleoclimate history from these two basins.

High resolution XRF scans of Ca, Br, Fe and Sr as well as loss on ignition show a marked change around 3700 cal yBP that correlates with the top of a peat layer in Shad Pond and potential rapid sea level rise. This is followed by a period of high variability from 3700 yBP until approximately 2000 yBP possibly representing wet/dry cycles. This is corroborated by the ∂¹⁸O record recovered from ostracode shells as well as their trace element Mg:Ca and Sr:Ca ratios. The ∂¹⁸O records show an overall depletion from +1.47 ppm to -2.04 ppm (VPDB) throughout the 6000 year record, with highest variability between the 4000-3000 yBP period. Trace element analyses reveal a Mg:Ca and Sr:Ca record that positively co-varies and trends with the ∂¹⁸O record. Evidence for a meteoric lens collapse at 1.6-1.8 ka as sea-level rise breached a local sill and altered coastal circulation in Shad Pond is also apparent. Despite the differences in lake type (i.e. coastal lagoon vs. blue hole), the records from these two lakes show similar paleoclimatic trends. These multi-proxy records correspond to other patterns seen regionally in the Caribbean as well as globally.