SEDIMENTARY STRUCTURES IN CARBONATE EOLIANITES AS INDICATORS OF CLIMATE INSTABILITY AND INTENSE STORMS DURING THE LAST INTERGLACIAL; ELEUTHERA ISLAND, BAHAMAS

Carbonate sediments in Bahamas can cement quite rapidly, preserving primary sedimentary structures, which in turn, can record certain climatic conditions. Situated on the eastern margin of the Bahamas platform, the carbonate eolianites of Eleuthera Island are particularly sensitive to changes in the Westerlies and Trade wind belts, as well as the impacts of hurricanes and tropical storms.

In order to better understand the climatic shifts of the last interglacial (MIS 5e), sedimentary structures such as cross-bed geometry, rhizomorphs, fenestral porosity, and grain composition have been examined in detail at a previously undescribed MIS 5e eolianite exposure along Thomas Street, in the town of Tarpum Bay. The sedimentary structures within the road cut show that dune deposition occurred rapidly, with limited lateral migration. This is indicated by well-preserved backset and topset bedding, trees buried in upright growth position, and a notable lack of rhizomorphs. In addition, the impacts of storm waves are recorded by numerous fenestrae-rich beds, which can be found in the eolianite at multiple horizons, often in association with scour marks and rip-up clasts.

In addition to the Thomas Street exposure, eight other MIS 5e eolianite localities on Eleuthera exhibit sedimentary structures indicative of rapid deposition, limited migration, and intense storm-wave activity. At low elevations, MIS 5e dunes were reworked by high energy waves, forming storm beach ridges with abundant fenestral beds, while at higher and/or distal locations, eolian fenestrae beds are present but fewer, in some cases up to 43 meters above sea-level. Collectively, this suggests a destabilization of climate and intensification of storms at the end of the last interglacial, which has serious implications for our future climate.