9617297 Jahnke Knowledge of the factors that control dissolution of CaCO3 and hence, preservation, is critical to the interpretation of the CaCO3 sedimentary record and to the prediction of the linkages between sedimentary CaCO3 , ocean chemistry and processes, and future climates. Recent results indicate that several aspects of CaCO3 dissolution, especially dissolution driven by the metabolic production of CO2 in sediment pore waters, are poorly constrained. This has been demonstrated by: 1. regional variations in the extent of metabolic dissolution observed in in situ benthic flux chamber incubations, 2. the lack of significant change in the rate of dissolution calculated from in situ pore water studies across the saturation horizon, and 3. the presence of aragonite in surface sediments that are overlain by undersaturated bottom waters. Two of the three regions, the Cape Verde Plateau, Ontong Java Plateau and Cape Hatteras continental rise, that have been studied previously will be revisited to further constrain CaCO3 dissolution mechanisms. Specifically, fine- scale pore water samples at in situ temperature and pressure will be analyzed for Ca2+ and trace metals. These results will augment the data sets already obtained for these regions previously. In addition, in situ benthic flux chamber incubations will be conducted to: 1. examine whether chamber artifacts have influenced previous results, 2. determine if fine-scale pore water Ca2+ gradients support present dissolution models and agree with chamber measurements, 3. examine whether other acid base reactions are influencing predicted metabolic dissolution rates, 4. assess variations in the mineralogy and reactivity of the carbonate phases between the study sites, and 5. determine whether exchange reactions at the carbonate mineral surface can account for the variations in metabolic dissolution observed. ***
