Selenium isotopes support free O2 in the latest Archean

Research Article| March 01, 2015 Selenium isotopes support free O2 in the latest Archean Eva E. Stüeken; Eva E. Stüeken * 1Department of Earth & Space Sciences and Astrobiology Program, University of Washington, Seattle, Washington 98195-1310, USA *E-mail: evast@uw.edu Search for other works by this author on: GSW Google Scholar Roger Buick; Roger Buick 1Department of Earth & Space Sciences and Astrobiology Program, University of Washington, Seattle, Washington 98195-1310, USA Search for other works by this author on: GSW Google Scholar Ariel D. Anbar Ariel D. Anbar 2School of Earth & Space Exploration, Arizona State University, Tempe, Arizona 85287, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Eva E. Stüeken * 1Department of Earth & Space Sciences and Astrobiology Program, University of Washington, Seattle, Washington 98195-1310, USA Roger Buick 1Department of Earth & Space Sciences and Astrobiology Program, University of Washington, Seattle, Washington 98195-1310, USA Ariel D. Anbar 2School of Earth & Space Exploration, Arizona State University, Tempe, Arizona 85287, USA *E-mail: evast@uw.edu Publisher: Geological Society of America Received: 25 Aug 2014 Revision Received: 31 Dec 2014 Accepted: 22 Jan 2015 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2015 Geological Society of America Geology (2015) 43 (3): 259–262. https://doi.org/10.1130/G36218.1 Article history Received: 25 Aug 2014 Revision Received: 31 Dec 2014 Accepted: 22 Jan 2015 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Eva E. Stüeken, Roger Buick, Ariel D. Anbar; Selenium isotopes support free O2 in the latest Archean. Geology 2015;; 43 (3): 259–262. doi: https://doi.org/10.1130/G36218.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Selenium (Se) undergoes redox transformations and isotopic fractionations at relatively high redox potentials and could therefore provide insight into changes in oceanic and atmospheric O2 levels over Earth's history. We test this idea with Se data from the 2.5 Ga Mount McRae Shale (Hamersley Basin, Australia), which records temporary enrichments in abundances and isotopes of other redox-sensitive elements indicating a "whiff of oxygen" in Earth's atmosphere before the Great Oxidation Event. Se isotopic ratios expressed as δ82/78Se and abundances relative to crustal background show significant positive excursions of up to 1.1‰ and an enrichment 13 times above background, respectively, overlapping with excursions in Mo and N isotopes and abundances. Because Se has a relatively high redox potential and photosynthetic oxidation pathways are unknown, our data thus suggest that Se was mobilized by free O2 during this interval. The isotopic fractionation likely occurred during transport of Se oxyanions from the site of weathering to the outer shelf. Although O2 could have been produced locally on land and may not necessarily have increased in the global atmosphere, our results strengthen the inference of an early origin of oxygenic photosynthesis long before the Paleoproterozoic Great Oxidation Event. This is the first report of a Se isotope excursion in the Precambrian rock record, and it confirms that Se isotopes can serve as a useful redox proxy in deep time. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.