Chromium Cycling in Redox-Stratified Basins Challenges δ 53 Cr Paleoredox Proxy Applications.

Autor: Janssen DJ; Institute of Geological Sciences University of Bern Bern Switzerland.; Oeschger Centre for Climate Change Research University of Bern Bern Switzerland.; Department Surface Waters Eawag: Swiss Federal Institute of Aquatic Science and Technology Kastanienbaum Switzerland., Rickli J; Institute of Geological Sciences University of Bern Bern Switzerland.; Oeschger Centre for Climate Change Research University of Bern Bern Switzerland.; Institute of Geochemistry and Petrology Department of Earth Sciences ETH Zurich Zurich Switzerland., Wille M; Institute of Geological Sciences University of Bern Bern Switzerland., Sepúlveda Steiner O; Department Surface Waters Eawag: Swiss Federal Institute of Aquatic Science and Technology Kastanienbaum Switzerland., Vogel H; Institute of Geological Sciences University of Bern Bern Switzerland.; Oeschger Centre for Climate Change Research University of Bern Bern Switzerland., Dellwig O; Marine Geology Leibniz Institute for Baltic Sea Research Rostock Germany., Berg JS; Institute of Earth Surface Dynamics University of Lausanne Lausanne Switzerland., Bouffard D; Department Surface Waters Eawag: Swiss Federal Institute of Aquatic Science and Technology Kastanienbaum Switzerland.; Institute of Earth Surface Dynamics University of Lausanne Lausanne Switzerland., Lever MA; Department of Environmental Systems Science ETH-Zurich Zurich Switzerland.; Now at Marine Science Institute University of Texas at Austin TX Port Aransas USA., Hassler CS; Department F.-A. Forel for Environmental and Aquatic Sciences University of Geneva Geneva Switzerland.; Institute of Earth Sciences University of Lausanne Lausanne Switzerland., Jaccard SL; Institute of Geological Sciences University of Bern Bern Switzerland.; Oeschger Centre for Climate Change Research University of Bern Bern Switzerland.; Institute of Earth Sciences University of Lausanne Lausanne Switzerland.
Jazyk: angličtina
Zdroj: Geophysical research letters [Geophys Res Lett] 2022 Nov 16; Vol. 49 (21), pp. e2022GL099154. Date of Electronic Publication: 2022 Oct 28.
DOI: 10.1029/2022GL099154
Abstrakt: Chromium stable isotope composition (δ 53 Cr) is a promising tracer for redox conditions throughout Earth's history; however, the geochemical controls of δ 53 Cr have not been assessed in modern redox-stratified basins. We present new chromium (Cr) concentration and δ 53 Cr data in dissolved, sinking particulate, and sediment samples from the redox-stratified Lake Cadagno (Switzerland), a modern Proterozoic ocean analog. These data demonstrate isotope fractionation during incomplete (non-quantitative) reduction and removal of Cr above the chemocline, driving isotopically light Cr accumulation in euxinic deep waters. Sediment authigenic Cr is isotopically distinct from overlying waters but comparable to average continental crust. New and published data from other redox-stratified basins show analogous patterns. This challenges assumptions from δ 53 Cr paleoredox applications that quantitative Cr reduction and removal limits isotope fractionation. Instead, fractionation from non-quantitative Cr removal leads to sedimentary records offset from overlying waters and not reflecting high δ 53 Cr from oxidative continental weathering.
(© 2022. The Authors.)
Databáze: MEDLINE
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