HURRICANES AND THEIR EFFECT ON SEDIMENTATION AND FAUNAL DYNAMICS IN TWO TROPICAL SALINE LAKES

A multi-proxy analysis involving organic content, dry bulk density, grain size, sediment fabric, Mg/Ca and Sr/Ca trace elements, oxygen and carbon isotopes and ostracode and mollusk faunal composition was performed on six cores from Storr's Lake and Salt Pond, two saline inland ponds on San Salvador Island, Bahamas. The lacustrine sedimentation and fossil record of these ponds is punctuated by intervals of carbonate sand deposition from hurricane washover. These storm deposits have been surficially mapped from the last hurricane, Frances, which was a CAT 4 storm that passed over the island in 2004. This storm as well as other historical storms can be identified in the cores by the sand size fraction, as well as an increase in dry bulk density at those intervals. Four primary facies were identified based on grain size, bedding features and composition-- including evaporites and flocculated mud, carbonate mud, algal laminated mud and carbonate sand. Faunal diversity was assessed throughout the cores at 1 cm intervals, revealing patterns that suggest that species richness and abundance increased after large storm events, possibly due to the freshening that occurred from the storm. In addition, stromatolitic algal mats found in both lakes increase in their productivity after each event. A depositional model for these two lakes is proposed and their history is linked to Holocene sea level fluctuations. In addition, the intense hurricane activity of the 1930's is recorded in these cores which has been linked to changes in sea surface temperatures that resulted in the severe drought or ‘dust bowl' conditions in the United States in the 1930's.