Trace Metal-Organic Interactions In Sediments and the Preservation of Paleoredox Proxies
To address this issue, we have undertaken a field-based experiment to test the hypothesis that porewater redox conditions are recorded in the concentrations of trace metals bound in the sedimentary organic carbon (OC) pool. We have collected sediments from several modern anoxic/euxinic basins: the central Black Sea, the Orca Basin, the Cariaco Basin, and Effingham Inlet, Vancouver Island. These environments vary in terms of bottomwater oxygen and dissolved sulfide concentrations, and the sediments are characterized by variations in organic carbon and iron sulfide geochemistry. Preliminary results suggest that variations in the ratios of aromatic to saturate hydrocarbons may control the speciation of metals in the organic carbon pool, with differences that correlate to bottomwater redox. The results of this study will further refine conceptual models that govern the use of trace metals and organic carbon as paleoceanographic proxies and provide an initial framework to assess the potential use of specific organo-metallic biomarkers (such as metallo-proteins) in paleoenvironmental studies.