Pore Water Estimates of the Radiocarbon Age of Calcite Dissolving at the Sea Floor

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ABSTRACTOCE-9810962One of the ways scientists try to understand the the history of biological production in the ocean and its relationship to climatic history through the carbon cycle is through examination of the sedimentary record of marine carbonates. Interpretation of changes in glacial/interglacial carbonate accumulation rates requires that we understand the mechanism(s) of calcite dissolution, and until now investigators have tried to approach this problem indirectly by estimating the amount of CaCO3 remaining after dissolution. The two candidate mechanisms most widely considered are chemical erosion, in which the carbonate sediment uniformly dissolves, and non-homogeneous dissolution, in which the dissolution is not uniform. In this project, the PIs will develop and use a direct method for determining the dissolution mechanism by determining radiocarbon ages of inorganic carbon in sediment porewaters generated by CaCO3 dissolution and by the oxidation of organic matter. A full suite of carbon and carbon isotopic measurements will be made on solids and porewaters in sediments from the Eastern Equatorial Atlantic and the Western Equatorial Pacific to give a fresh evaluation of the mechanism of dissolution.