Fully oxygenated water columns over continental shelves before the Great Oxidation Event


Late Archaean sedimentary rocks contain compelling geochemical evidence for episodic accumulation of dissolved oxygen in the oceans along continental margins before the Great Oxidation Event. However, the extent of this oxygenation remains poorly constrained. Here we present thallium and molybdenum isotope compositions for anoxic organic-rich shales of the 2.5-billion-year-old Mount McRae Shale from Western Australia, which previously yielded geochemical evidence of a transient oxygenation event. During this event, we observe an anticorrelation between thallium and molybdenum isotope data, including two shifts to higher molybdenum and lower thallium isotope compositions. Our data indicate pronounced burial of manganese oxides in sediments elsewhere in the ocean at these times, which requires that the water columns above portions of the ocean floor were fully oxygenated—all the way from the air–sea interface to well below the sediment–water interface. Well-oxygenated continental shelves were probably the most important sites of manganese oxide burial and mass-balance modelling results suggest that fully oxygenated water columns were at least a regional-scale feature of early Earth’s oceans 2.5 billion years ago.

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Fig. 1: Illustration of a possible well-oxygenated marine margin before the GOE.
Fig. 2: Geochemical profiles in organic-rich shales from the Mount McRae Shale.
Fig. 3: Mo and Tl isotope cross-plot from the upper shale member.

Data availability

All data generated during this study are included in the Supplementary Information.

Change history

  • 06 March 2019

    An amendment to this paper has been published and can be accessed via a link at the top of the paper.


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We would like to thank W. Zheng and J. Blusztajn for their help with instrumental analysis at Arizona State University and the Woods Hole Oceanographic Institution, respectively. This research was supported financially by the NSF Frontiers in Earth System Dynamics programme (award no. NSF EAR-1338810), the NSF Chemical Oceanography programme (award no. OCE 1434785), the NASA Exobiology programme (award no. NNX16AJ60G), an NSERC Discovery Grant (award no. RGPIN-435930) and the NASA Astrobiology Institute (award no. NNA15BB03A). This material is based on work supported by the National Science Foundation Graduate Research Fellowship Program under grant no. 026257-001. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Author information




C.M.O., S.G.N., J.D.O., B.K., and A.D.A. developed the project idea. C.M.O. processed samples and performed Tl and Mo isotope analyses with contributions from S.G.N., J.D.O., B.K., G.W.G. and S.J.R. C.M.O. performed the modelling and wrote the manuscript with contributions from all co-authors.

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Correspondence to Chadlin M. Ostrander.

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Supplementary information

Supplementary text and figures

Supplementary sample information, modelling, Supplementary Figs 1, 2 and Supplementary Tables 1, 2.

Supplementary data

Trace metal and isotope data for Mt. McRae shale samples.

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Ostrander, C.M., Nielsen, S.G., Owens, J.D. et al. Fully oxygenated water columns over continental shelves before the Great Oxidation Event. Nat. Geosci. 12, 186–191 (2019). https://doi.org/10.1038/s41561-019-0309-7

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