HR: 17:20h
AN: U12B-05    [PDF]
TI: Phosphorus: Sedimentary Geochemistry, Mass Balance, and Ocean History From ODP Sediments
AU: * Delaney, M L
EM: delaney@ucsc.edu
AF: Ocean Sciences/IMS, University of California, Santa Cruz, CA 95064
AB: Phosphorus is a key nutrient fueling oceanic primary productivity, exerting critical control on geological time scales on productivity and potential organic carbon burial. Primary productivity plays a critical role in the delivery of phosphorus to sediments via organic matter export from the surface ocean and delivery to sediments. The fluxes of phosphorus to and from the ocean through time are driven by factors such as changes in continental weathering and in oceanic biogeochemical processes and their effects on sedimentation. Material recovered by the Ocean Drilling Program has been essential to deciphering the sedimentary geochemistry of phosphorus and its ocean history through time. We demonstrate that the burial of phosphorus in marine sediments on depths scales of tens to hundreds of meters is controlled by geochemical transformations in the sediment resulting from microbially mediated organic matter oxidation. These transformations are often reflected in interstitial water geochemistry as well, and they have significant influence on carbon/phosphorus burial ratios. These result in a widely disseminated authigenic phase, presumably carbonate fluorapatite. This phase is present at low concentrations in all of the marine sediments we have examined, and is therefore a major sink for oceanic phosphorus burial. Determining the geochemistry and concentration of phosphorus burial provided us the basis for records of phosphorus accumulation in sediments, which we coupled with multi-proxy investigations of tracers related to export productivity (barium excess), biogenic sediment accumulation (opal and calcium carbonate), and sedimentary redox state (sediment trace metals, interstitial water geochemistry). I use several examples to illustrate P burial responses on different timescales in intervals of carbon cycle and/or climate change. These will also be used to demonstrate the fruitful lessons we have learned about geochemical methods, age models and physical properties, and the challenges and value of multi-proxy approaches to ocean history.
DE: 1030 Geochemical cycles (0330)
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1615 Biogeochemical processes (4805)
DE: 4267 Paleoceanography
DE: 9604 Cenozoic
SC: U
MN: 2003 Fall Meeting