Phosphorus Accumulation in Cenozoic Marine Sediments

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9416593 DELANEY The supply of dissolved phosphorus to the oceans from continental weathering plays a key role in regulating oceanic productivity and sediment burial on long time scales. Despite this importance, little is known about the Cenozoic history of P fluxes to and from the ocean. The three main objectives of this research are: (1) to understand the controls on P accumulation rates in Cenozoic marine sediments, and (3) to interpret these P accumulations rate variations using mass balance models. Measurements of P geochemical distributions in marine sediments will use established sequential extraction techniques which differentiate five sedimentary P components; four of these are burial sinks for dissolved, reactive P and the fifth is detrital P. P accumulation rates will be calculated from total reactive P concentration measurements. Total P concentration measurements will also be applied, by shorter analytical methods, to the determination of P accumulation rates where it has been demonstrated that detrital P is a negligible contribution to total P. Sites to be studied to understand the controls on P accumulation rates include depth transects of sites with similar surface water productivity , latitudinal transects of sites along a gradient of productivity, and sediments of different lithologies. Sites for the documentation of temporal variations in P accumulation rates in Cenozoic marine sediments will be selected to ensure geographic coverage of regions significant in terms of global productivity and sediment accumulation (including the equatorial regions of the Atlantic and Pacific, the high latitude North Pacific, and the Southern Ocean). Interpretation of the Cenozoic record of P accumulation will be linked to other geochemical records of ocean history, such as strontium and carbon isotopes. This work will yield substantial insights into the variations in P fluxes to and from the oceanic reservoir over long time scales.