AN OXYGEN ISOTOPE PALEOCLIMATE RECORD FROM DUCK POND BLUE HOLE AND SHAD POND ON ELEUTHERA, BAHAMAS

Oxygen isotope and Mg:Ca and Sr:Ca records for the past 6,000 years have been recovered from two lakes on the island of Eleuthera, Bahamas. 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 151 cm 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 ostracods 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 ostracod shells as well as their trace element Mg:Ca and Sr:Ca ratios. The ∂¹⁸O records show an overall depletion 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 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 record climate-driven changes in the Late Holocene. These multi-proxy records correspond to other patterns seen regionally in the Caribbean as well as globally.