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The isotopic composition of authigenic chromium in anoxic marine sediments: A case study from the Cariaco Basin

Reinhard, Christopher T. and Planavsky, Noah J. and Wang, Xiangli and Fischer, Woodward W. and Johnson, Thomas M. and Lyons, Timothy W. (2014) The isotopic composition of authigenic chromium in anoxic marine sediments: A case study from the Cariaco Basin. Earth and Planetary Science Letters, 407 . pp. 9-18. ISSN 0012-821X.

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Chromium (Cr) isotopes are an emerging proxy for tracking redox processes at the Earth's surface. However, there has been limited exploration of the Cr isotope record of modern and recent marine sediments. The basic inorganic chemistry of Cr suggests that anoxic marine basins should factor prominently in the global Cr cycle and that sediments deposited within anoxic basins may offer a valuable Cr isotope archive throughout Earth's history. Here, we present δ^(53)Cr data from sediments of the Cariaco Basin, Venezuela—a ‘type’ environment for large, perennially anoxic basins with a relatively strong hydrological connection to the global oceans. We document a marked positive shift in bulk δ^(53)Cr values following the termination of the Last Glacial Maximum, followed by relative stasis. Based on a suite of independent redox proxies, this transition marks a switch from oxic to persistently anoxic and sulfidic (euxinic) depositional conditions within the basin. We find good agreement between two independent approaches toward estimating the δ^(53)Cr composition of authigenic Cr in euxinic Cariaco Basin sediments and that these estimates are very similar to the δ^(53)Cr composition of modern open Atlantic Ocean seawater. These data, together with considerations of reaction kinetics and mass balance within the Cariaco Basin, are consistent with the hypothesis that anoxic marine settings can serve as a chemical archive of first-order trends in seawater δ^(53)Cr composition. Additionally, the Cariaco Basin data suggest that there has been secular stability in the average δ^(53)Cr value of Atlantic seawater over the last ∼15 kyr.

Item Type:Article
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URLURL TypeDescription Material
Reinhard, Christopher T.0000-0002-2632-1027
Fischer, Woodward W.0000-0002-8836-3054
Additional Information:© 2014 Elsevier B.V. Received 12 July 2013, Revised 15 September 2014, Accepted 17 September 2014, Available online 3 October 2014. Editor: G.M. Henderson. The authors thank Britney Katz and Steve Bates for assistance in the lab. The comments and critical evaluation of Ronny Schoenberg and an anonymous reviewer greatly improved the manuscript. This research was supported through funding from the National Aeronautics and Space Administration (NASA), Exobiology Program, Award #NNX12AD84G. C.T.R. acknowledges support from the O.K. Earl Fellowship in The Division of Geological and Planetary Sciences at California Institute of Technology. N.J.P. acknowledges support from a NSF-EAR-PF, Award #1144317.
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O.K. Earl Postdoctoral Fellowship, CaltechUNSPECIFIED
Subject Keywords: anoxia; euxinia; paleoredox; glacial–interglacial; oxygen
Record Number:CaltechAUTHORS:20141219-120347271
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Official Citation:Christopher T. Reinhard, Noah J. Planavsky, Xiangli Wang, Woodward W. Fischer, Thomas M. Johnson, Timothy W. Lyons, The isotopic composition of authigenic chromium in anoxic marine sediments: A case study from the Cariaco Basin, Earth and Planetary Science Letters, Volume 407, 1 December 2014, Pages 9-18, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53046
Deposited By: Ruth Sustaita
Deposited On:19 Dec 2014 20:28
Last Modified:09 Mar 2020 13:19

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