High-Resolution 230Th Profiles in Carbonate Sediments: A Signal from Steady-State Dissolution?

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ABSTRACTOCE-0099016The problem being addressed in this proposal, dissolution mechanisms in deep sea carbonate sediments, is essential to the interpretation of paleo-climate records and to provide a robust assessment of the role of the carbonate pump in the global carbon cycle. The approach suggested here is an extension of the PI's previous NSF award investigating non-homogeneous carbonate dissolution. Since the rain-rates of CaCO3 and 230Th to sediments should remain constant over time, variations in the 230 Th normalized accumulation rate of CaCO3 should provide a sensitive and independent indicator of any variable CaCO3 dissolution.. The PI proposes to use this at a number of selected and well-characterized sites (e.g. Ontong-Java Plateau in western Eq..Pac; Ceara Rise in west. Eq. Atl; Sierra Leone Rise and Cape Verde Plateau in east. Eq. Atl.) which he has sampled during the past decade. Correlation of the high spatial resolution (2 -3mm) 230Th analyses with those factors thought to control CaCO3 dissolution (such as sediment composition, sediment mixing rates, pore water chemistry, pH, dissolved oxygen and organic carbon etc) will be undertaken for these sediment cores. Radiocarbon (14C) ages of calcite dissolving at the sea floor provides a centennial to millennial timescale with which to observe and interpret more complex mixing models for carbonate dissolution occurring in the deep sea sedimentary record. The interpretation of past climatic change through studying carbonate sediment accumulation in the deep ocean is recognized as being an important component of climate change research.