9729262 Yemane Quaternary Caribbean climates are predominantly derived from data collected from environments. Based on micropaleontological data CLIMAP concluded that the tropical ocean belt during the Quaternary had sea surface temperatures (SST) similar to or slightly warmer than the present, and that there was no warming between the Last Glacial Maximum (LGM) and the Holocene. (18O values of planktonic foraminifera infer small (<3(C) temperature changes whereas, those on corals suggest that early Holocene SST for the tropical ocean dropped by as much as 6.5(C than the present. Another study on rare gasses dissolved in ice age ground water suggest that LGM temperatures were 5(C colder than today's surface continental temperatures. Similarly, COHMAP numerical models based on general circulation patterns suggest a cooler tropical ocean where the average annual temperature may have been as low as 7-9(C cooler during the Last Glacial Maximum (LGM), but steadily increased to the present. Although post-glacial anomalies show that tropical climate is sensitive to subtle changes in climate forcing mechanisms, the tropics are generally presumed to have buffered the effects of recent climate changes. Since SST's may not accurately reflect terrestrial climates, it is necessary to obtain independent paleoclimatic data from terrestrial environments. Continental datasets, such as from speleothems in Puerto Rico, can be used to evaluate the published climatic retrodictions and numerical climate models for the Caribbean, as well as perhaps assist in predicting future climate trends. Speleothems form by the precipitation of CaCO3 as vadose seepage waters enter a cave and lose CO2 to the cave atmosphere. Assuming that calcite deposition had occurred under conditions of oxygen isotope equilibrium, (18O measurements of the cave calcite would reflect surface paleotemperatures. The proposed study aims to establish a paleotemperature proxy record from Puerto Rico, which will broaden the database fo r Quaternary climate changes in the tropics. Thickness of carbonate growth layers will be measured to determine the rate of growth. Cathodoluminescent, UV-fluorescence, and XRD studies on individual growth layers will be used to evaluate recrystallisation, carbonate alteration, and organic matter input. Concentration of trace and ultra-trace elements in the speleothem samples will be measured by ICP-AES. Absolute chronostratigraphy will be established on strategically selected samples by 230Th/234U series method using high-precision thermal ionization mass spectrometer. (18O and (13C ratios will be measured on samples collected along the axis of the speleothem on a high-precision automated mass spectrometer. The resulting paleotemperature record will be compared to published data, as well as will be used to constrain the climatic and hydrologic processes on continental masses in the Caribbean Sea.
