HR: 15:10h
AN: PP32C-07    [PDF]
TI: Testing the Phosphorus Paleoproductivity Proxy Across a Productivity and Sedimentology Gradient in the Southern Ocean
AU: * Latimer, J C
EM: jclatime@iupui.edu
AF: Indiana University, Department of Geological Sciences 1001 E. 10th St., Bloomington, IN 47405 United States
AU: * Latimer, J C
EM: jclatime@iupui.edu
AF: Indiana/Purdue University at Indianapolis, Geology Department 723 W. Michigan St., Indianapolis, IN 46202 United States
AU: Filippelli, G M
EM: gfilippe@iupui.edu
AF: Indiana/Purdue University at Indianapolis, Geology Department 723 W. Michigan St., Indianapolis, IN 46202 United States
AB: Because of its role in biological productivity and its tendency to be preserved in sediments, records of phosphorus (P) burial (reactive P concentrations and accumulation, P/Ti ratios) have been used as proxies of export production. Unlike organic C, P is redistributed into different sedimentary pools during diagenesis and much of the sedimentary P flux to the seafloor may actually be retained in sediments in certain depositional environments. At three sites in the southeastern Atlantic Ocean and one site off the coast of Tasmania, we have systematically compared detailed P geochemistry with P/Ti ratios from bulk sediment geochemistry. We have verified that in these settings P/Ti ratios reflect the reactive P component, which is indicative of P that was once bioactive. However, based on quantification of opal intrinsic P, we have discovered that the commonly used SedEx reaction scheme does not liberate organic P found within opal. P/Ti ratios are a useful proxy because the ratios are resistant to the effects of dissolution and potentially sediment focusing, and they are not influenced by sediment type. Using downcore P/Ti ratios as a proxy for export production in the Southern Ocean is particularly useful because of the variability in sediment type and the paucity of carbonate at some sites. Surprisingly, maxima in P/Ti ratios over the last 1 Ma tend to occur at all sites at glacial terminations, regardless of position relative to important frontal zones. These findings are in contrast to other work suggesting that productivity north and south of the Antarctic Polar Front is opposite on glacial/interglacial time scales. We suggest that the increases in export production at terminations are related to changes in surface ocean circulation, nutrient delivery, and sea-ice interactions.
DE: 4805 Biogeochemical cycles (1615)
DE: 4825 Geochemistry
DE: 4845 Nutrients and nutrient cycling
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting