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Published January 5, 2022 | Supplemental Material + Published
Journal Article Open

Reexamination of 2.5-Ga "whiff" of oxygen interval points to anoxic ocean before GOE


Transient appearances of oxygen have been inferred before the Great Oxygenation Event (GOE) [∼2.3 billion years (Ga) ago] based on redox-sensitive elements such as Mo and S—most prominently from the ∼2.5-Ga Mount McRae Shale in Western Australia. We present new spatially resolved data including synchrotron-based x-ray spectroscopy and secondary ion mass spectrometry to characterize the petrogenesis of the Mount McRae Shale. Sediments were primarily composed of organic matter and volcanic ash (a potential source of Mo), with U-Pb ages revealing extremely low sedimentation rates. Catagenesis created bedding-parallel microfractures, which subsequently acted as fluid pathways for metasomatic alteration and recent oxidative weathering. Our collective observations suggest that the bulk chemical datasets pointing toward a "whiff" of oxygen developed during postdepositional events. Nonzero Δ³³S in trace-metal–poor, early diagenetic pyrite and the unusually enriched organic carbon at low sedimentation rates instead suggest that environmental oxygen levels were negligible ∼150 million years before the GOE.

Additional Information

© 2022 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). Submitted 27 May 2021; Accepted 17 November 2021; Published 5 January 2022. We thank T. Present and Y. Guan for aid in SIMS data collection. We acknowledge the anonymous reviewers who gave critical and useful comments that greatly improved the manuscript. This research was supported by the Agouron Institute, NASA Exobiology, NSF-EAR 0739105 (T.D.R. and J.L.K.), the Packard Foundation, NSF Graduate Research Fellowships (S.P.S. and J.E.J.), and NASA Earth and Space Science Fellowship (S.P.S.). Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract no. DE-AC02-76SF00515. Author contributions: T.D.R., J.L.K., W.W.F., B.R., S.P.S., and J.E.J. designed research. T.D.R., W.W.F., and B.R. studied and sampled the rock cores. T.D.R., S.P.S., J.E.J., and W.W.F. performed secondary ion mass spectrometry analyses. S.P.S., J.E.J., and W.W.F. performed petrography and electron microscopy. S.P.S., J.E.J., S.M.W., and W.W.F. performed synchrotron-based spectroscopy. B.R. and J.-W.Z. developed geochronological data. S.P.S., J.E.J., W.W.F., B.R., and J.L.K. wrote the paper. The authors declare that they have no financial or other competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials.

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Published - sciadv.abj7190.pdf

Supplemental Material - sciadv.abj7190_dataset_s1.zip

Supplemental Material - sciadv.abj7190_sm.pdf


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August 22, 2023
October 23, 2023