EVIDENCE OF CLIMATE CHANGE DURING THE LAST INTERGLACIAL FROM EOLIAN AND NEARSHORE CARBONATES: SAN SALVADOR ISLAND, BAHAMAS

In order to examine the potential of future climate change, it is important to understand the climate at the end of the last peak interglacial (marine oxygen isotope substage 5e). The carbonate facies of the Bahamas are extremely sensitive to climatic shifts, which are recorded by various sedimentary structures. San Salvador is located on the windward margin of the Bahamas Platform and thus preserves a high resolution record of conditions during the last interglacial.

Prior studies of sedimentary structures on nearby Eleuthera indicate that climate deteriorated rapidly at the close of the last interglacial, resulting in dramatic sea-level fluctuations and an intensification of tropical storms. In order to further characterize climate during the last interglacial, sedimentary structures such as cross-bed geometry, rhizomorphs, bubble fenestrae (keystone vugs), grain composition, and paleosols have been examined within a sequence stratigraphic framework at several localities on San Salvador.

Preliminary results from San Salvador are as follows: (1) last interglacial facies range from reef, to subtidal, to beach through dune and can be distinguished through quantification of their sedimentary structures; (2) backset and topset dominated bedding, and scarcity of rhizomorphs in last interglacial eolianites imply rapid deposition with limited lateral migration; and (3) bubble fenestrae beds exposed in last interglacial dune ridges (+12m) were likely formed by the impact of storm waves, perhaps combined with windborne spray. Collectively, the sedimentary structures within eolian and nearshore facies on San Salvador suggest a destabilization of climate at the end of the last interglacial.