Emerging geochemical evidence suggests considerable redox heterogeneity in the mid-Proterozoic ocean. However, quantitative estimates of the extent of different modes of anoxia remain poorly constrained. Due to their complementary redox-related behavior, uranium and molybdenum isotope data can be combined to reconstruct ancient marine redox landscapes, but this approach has not been applied to the mid-Proterozoic. We present new δ238U and δ98Mo data for marine rocks from the ca. 1.4 Ga Xiamaling Formation, North China craton, together with independent redox indicators (Fe speciation and redox-sensitive trace metals). We find that most samples deposited under oxic or dysoxic conditions retain low U and Mo contents, with δ238U and δ98Mo values indistinguishable from continental crust, demonstrating a dominant detrital signal. By contrast, euxinic samples with authigenic enrichments in U and Mo record the highest authigenic δ238U and δ98Mo values, consistent with efficient reduction of U and Mo. Samples deposited under ferruginous conditions exhibit a wider range of intermediate δ238U and δ98Mo values that generally fall between the (dys)oxic and euxinic end-members. Using a coupled U-Mo isotope mass balance model, we infer limited euxinia (<0.5% of the global seafloor area) but extensive low-productivity (dys)oxic and ferruginous settings in ca. 1.4 Ga oceans. This redox landscape would have provided potentially habitable conditions for eukaryotic evolution in the mid-Proterozoic.
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July 02, 2025
Early Publication
Tracking the spatial extent of redox variability in the mid-Proterozoic ocean Available to Purchase
Yafang Song;
Yafang Song
1
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK2
Deep Space Exploration Laboratory/State Key Laboratory of Lithospheric and Environmental Coevolution, University of Science and Technology of China, Hefei 230026, China
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Benjamin J.W. Mills;
Benjamin J.W. Mills
1
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
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Fred T. Bowyer;
Fred T. Bowyer
1
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
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Morten B. Andersen;
Morten B. Andersen
3
School of Earth and Environmental Sciences, Cardiff University, Cardiff CF10 3AT, UK
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Frantz Ossa Ossa;
Frantz Ossa Ossa
3
School of Earth and Environmental Sciences, Cardiff University, Cardiff CF10 3AT, UK4
Department of Earth Sciences, Khalifa University of Science and Technology, Abu Dhabi 127788, United Arab Emirates
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Alexander J. Dickson;
Alexander J. Dickson
5
Centre of Climate, Ocean and Atmosphere, Department of Earth Sciences, Royal Holloway University of London, Egham TW20 0EX, UK
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Jason Harvey;
Jason Harvey
1
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
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Shuichang Zhang;
Shuichang Zhang
6
Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, China National Petroleum Corporation, Beijing 100083, China
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Xiaomei Wang;
Xiaomei Wang
6
Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, China National Petroleum Corporation, Beijing 100083, China
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Huajian Wang;
Huajian Wang
6
Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, China National Petroleum Corporation, Beijing 100083, China
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Donald E. Canfield;
Donald E. Canfield
6
Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, China National Petroleum Corporation, Beijing 100083, China7
Nordcee, Department of Biology, University of Southern Denmark, Odense 5230, Denmark
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Graham A. Shields;
Graham A. Shields
8
Department of Earth Sciences, University College London, London WC1E 6BT, UK
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Simon W. Poulton
Simon W. Poulton
1
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK9
International Research Frontiers Initiative, Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8550, Japan
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Yafang Song
1
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK2
Deep Space Exploration Laboratory/State Key Laboratory of Lithospheric and Environmental Coevolution, University of Science and Technology of China, Hefei 230026, China
Benjamin J.W. Mills
1
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
Fred T. Bowyer
1
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
Morten B. Andersen
3
School of Earth and Environmental Sciences, Cardiff University, Cardiff CF10 3AT, UK
Frantz Ossa Ossa
3
School of Earth and Environmental Sciences, Cardiff University, Cardiff CF10 3AT, UK4
Department of Earth Sciences, Khalifa University of Science and Technology, Abu Dhabi 127788, United Arab Emirates
Alexander J. Dickson
5
Centre of Climate, Ocean and Atmosphere, Department of Earth Sciences, Royal Holloway University of London, Egham TW20 0EX, UK
Jason Harvey
1
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
Shuichang Zhang
6
Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, China National Petroleum Corporation, Beijing 100083, China
Xiaomei Wang
6
Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, China National Petroleum Corporation, Beijing 100083, China
Huajian Wang
6
Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, China National Petroleum Corporation, Beijing 100083, China
Donald E. Canfield
6
Key Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, China National Petroleum Corporation, Beijing 100083, China7
Nordcee, Department of Biology, University of Southern Denmark, Odense 5230, Denmark
Graham A. Shields
8
Department of Earth Sciences, University College London, London WC1E 6BT, UK
Simon W. Poulton
1
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK9
International Research Frontiers Initiative, Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8550, Japan
Publisher: Geological Society of America
Received:
21 Apr 2025
Revision Received:
30 May 2025
Accepted:
23 Jun 2025
First Online:
02 Jul 2025
Online ISSN: 1943-2682
Print ISSN: 0091-7613
© 2025 Geological Society of America
Geology (2025)
Article history
Received:
21 Apr 2025
Revision Received:
30 May 2025
Accepted:
23 Jun 2025
First Online:
02 Jul 2025
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CitationYafang Song, Benjamin J.W. Mills, Fred T. Bowyer, Morten B. Andersen, Frantz Ossa Ossa, Alexander J. Dickson, Jason Harvey, Shuichang Zhang, Xiaomei Wang, Huajian Wang, Donald E. Canfield, Graham A. Shields, Simon W. Poulton; Tracking the spatial extent of redox variability in the mid-Proterozoic ocean. Geology 2025; doi: https://doi.org/10.1130/G53447.1
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