MODELING THE INFLUENCE OF POST-DEPOSITIONAL PROCESSES ON THE PALEOCLIMATE RECORD FROM CARBONATE LACUSTRINE SEDIMENTS: LOUGH CARRA, WESTERN IRELAND

Stable oxygen and carbon isotopes from temperate carbonate lakes are commonly used as temperature and productivity proxies in paleoclimate studies. However, post-depositional processes that influence carbonate sediments in these lakes, and thus their paleoclimate record, are not well understood. The Keck Ireland Study Group retrieved several cores of recent carbonate deposits, up to 2.5 m in length, from Lough Carra in Western Ireland in the summers of 2002 and 2003. Porewater was extracted from the top 0.5 m of the cores and elemental analysis was performed to determine calcite saturation. Changes in calcite saturation states with depth indicate that dissolution of existing calcite and reprecipitation of new calcite occurs post-depositionally. The highly super-saturated conditions (~0.47 log IAP/kcal) found at depth (>45 cm) may be mediated by microbial processes, such as sulfate reduction. Wet and dry bulk densities, loss on ignition analyses and pore water analysis will be performed on the cores taken in 2003. These data will be used to model post-depositional processes and their influence on the stable isotope records in these lakes. This model will aid in our understanding of the processes that affect lacustrine carbonates and help to refine the paleoclimatic record obtained using the stable isotope analysis of these sediments.