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Development of a New Paleoceanographic Proxy: Correlating Excess Silver in Marine Sediments with Diatom Productivity and Redox Conditions

Meghan Wagner
University of Michigan Department of Geological Sciences Ann Arbor, Michigan
[email protected]

Understanding carbon burial in marine sediments represents a key link in both mitigating our effects on the carbon cycle, via the use of fossil fuels, and in discovering new sources of energy. Identification of environments where organic carbon is likely to be buried and removed from the short term carbon cycle provides a plausible avenue in which atmospheric CO2 may be drawn down and sequestered as primary production.

Silver has been proposed in the literature as both a paleoproductivity and paleoredox proxy. Similarities between Ag and silica in water column profiles have suggested a link between Ag and diatoms. This purported link predicts that enrichment of Ag should occur in sediments underlying regions of high diatom productivity. In the ocean, significant quantities of organic carbon are buried either under low-oxygen bottom waters or in places where surface productivity overwhelms the oxidation of organic matter below. Thus, Ag may leave not only a record of past surface productivity, but also bottom water redox conditions at the time of deposition.

Silver still requires development as a proxy, however. This project aims to determine if a link does exist between diatom surface productivity and the amount of Ag observed at the sediment-water interface below. We will extend known Ag sediment concentrations to Antarctic and Arctic sites, both regions where diatom productivity is high. If Ag is found to be enriched at these sites, this result will provide justification for pursuing Ag as a paleoproxy in ocean regions associated with high diatom biomass.


AAPG Search and Discovery Article #90094 © 2009 AAPG Foundation Grants in Aid