Authigenic uranium in foraminiferal coatings : a proxy for ocean redox chemistry
MetadataShow full item record
The rate of uranium accumulation in oceanic sediments from seawater is controlled by bottom water oxygen concentrations and organic carbon fluxes—two parameters that are linked to deep ocean storage of CO2. To investigate glacial-interglacial changes in what is known as authigenic U, we have developed a rapid method for its determination as a simple addition to a procedure for foraminiferal trace element analysis. Foraminiferal calcite acts as a low U substrate (U/Ca < 15 nmol/mol) upon which authigenic U accumulates in reducing sediments. We measured a downcore record of foraminiferal U/Ca from ODP Site 1090 in the South Atlantic and found that U/Ca ratios increase by 70–320 nmol/mol during glacial intervals. There is a significant correlation between U/Ca records of benthic and planktonic foraminiferal species and between U/Ca and bulk sediment authigenic U. These results indicate that elevated U/Ca ratios are attributable to the accumulation of authigenic U coatings in sediments. Foraminiferal Mn/Ca ratios were lower during the glacial intervals, suggesting that the observed U accumulation on the shells is not directly linked to U incorporation into secondary manganese phases. Thus, foraminiferal U/Ca ratios may provide useful information on past changes in sediment redox conditions.
Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 27 (2012): PA3227, doi:10.1029/2012PA002335.
Suggested CitationArticle: Boiteau, Rene M., Greaves, Mervyn, Elderfield, Henry, "Authigenic uranium in foraminiferal coatings : a proxy for ocean redox chemistry", Paleoceanography 27 (2012): PA3227, DOI:10.1029/2012PA002335, https://hdl.handle.net/1912/5763
Showing items related by title, author, creator and subject.
Authigenic iron oxide proxies for marine zinc over geological time and implications for eukaryotic metallome evolution Robbins, Leslie J.; Lalonde, Stefan V.; Saito, Mak A.; Planavsky, Noah J.; Mloszewska, A. M.; Pecoits, E.; Scott, C.; Dupont, C. L.; Kappler, A.; Konhauser, Kurt O. (2012-12)Here we explore enrichments in paleomarine Zn as recorded by authigenic iron oxides including Precambrian iron formations, ironstones and Phanerozoic hydrothermal exhalites. This compilation of new and literature-based ...
Zhou, Xiaoli; Jenkyns, Hugh C.; Lu, Wanyi; Hardisty, Dalton S.; Owens, Jeremy D.; Lyons, Timothy W.; Lu, Zunli (2017-03-15)Carbonate-associated iodine (I/Ca) has been used as a proxy of local, upper-ocean redox conditions, and has successfully demonstrated highly dynamic spatial and temporal patterns across different time scales of Earth ...
Morford, Jennifer L.; Martin, William R.; Carney, Caitlin M. (2009-01-23)We measured U in sediments (both pore waters and solid phase) from three locations on the middle Atlantic Bight (MAB) from the eastern margin of the United States: a northern location on the continental shelf off ...