A Whiff of Oxygen Before the Great Oxidation Event?
Ariel D. Anbar,1,2*
Yun Duan,1
Timothy W. Lyons,3
Gail L. Arnold,1
Brian Kendall,4
Robert A. Creaser,4
Alan J. Kaufman,5
Gwyneth W. Gordon,1
Clinton Scott,3
Jessica Garvin,6
Roger Buick6
High-resolution chemostratigraphy reveals an episode of enrichment of the redox-sensitive transition metals molybdenum and rhenium in the late Archean Mount McRae Shale in Western Australia. Correlations with organic carbon indicate that these metals were derived from contemporaneous seawater. Rhenium/osmium geochronology demonstrates that the enrichment is a primary sedimentary feature dating to 2501 ± 8 million years ago (Ma). Molybdenum and rhenium were probably supplied to Archean oceans by oxidative weathering of crustal sulfide minerals. These findings point to the presence of small amounts of O2 in the environment more than 50 million years before the start of the Great Oxidation Event.
1 School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA.
2 Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA.
3 Department of Earth Sciences, University of California, Riverside, CA 92521, USA.
4 Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E3.
5 Department of Geology, University of Maryland, College Park, MD 20742, USA.
6 Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA.
* To whom correspondence should be addressed. E-mail: anbar{at}asu.edu
