Abstract
The end-Triassic mass extinction was one of Earth’s largest biotic crises, and marine deoxygenation has been proposed as a primary driver. However, the timing, geographic extent, and severity of oxygen loss in the oceans remain uncertain. Here we present a multi-geochemical proxy record study from the equatorial Panthalassan Ocean that uses sedimentary iron speciation and nitrogen isotopes to reconstruct water column redox changes before, during, and after the mass extinction. Iron speciation data indicate anoxic bottom waters dominated this region through the Late Triassic-Early Jurassic, consistent with deposition beneath an oxygen minimum zone. Elevated nitrogen isotope values ~ 8 million years before the mass extinction record, enhanced denitrification linked to shoaling and expansion of this oxygen minimum zone. These results suggest that deoxygenation in the equatorial Panthalassa began well before the main extinction and coincided with biodiversity declines and carbon-cycle perturbations, likely stressing marine ecosystems before the end-Triassic mass extinction.
Data availability
The geochemical dataset generated for and analysed within this study is available in the Figshare repository, https://doi.org/10.6084/m9.figshare.31286599.
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Acknowledgements
We gratefully acknowledge the support for this study from United States National Science Foundation grant EAR-2026926 to B.C.G., A.H.C., and J.D.O. We also thank the Virginia Tech College of Science Dean’s Discovery Fund grant to BCG and National Geographic Society (NGS-9973-16) to AHC for financial support of the fieldwork. We thank the field crew who braved the Alaskan wilderness in 2017 and 2019 to collect samples that were instrumental to this work. We also thank Paul Claus and Ultima Thule Lodge for air support and National Park Service and Wrangell–St. Elias National Park and Preserve for access to the Grotto Creek site. The samples for this research were collected under research and collecting permits WRST-2017-SCI0004 and WRST-2018-SC1-0005. Finally, we thank the Communications Earth & Environment editors for handling our manuscript, as well as Dr. Shane Schoepfer and two anonymous reviewers for their constructive feedback that help improve our manuscript.
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K.E.M. conceived and designed the study, collected geochemical data, processed data, interpreted results, and led manuscript writing. S.M.M. conducted fieldwork, contributed to iron speciation acquisition, and contributed to manuscript review and editing. A.H.C. conducted fieldwork, developed the ammonoid biostratigraphic framework, contributed to manuscript review and editing, and acquired funding. J.D.O. conducted fieldwork, contributed to manuscript review and editing, and acquired funding. M.L.G. conducted fieldwork, contributed to manuscript review and editing, and provided conodont biostratigraphic and preservation expertise. R.E.R. supervised and assisted with nitrogen isotope analyses, contributed to data processing, and participated in manuscript review and editing. T.R.T. conducted fieldwork and contributed to manuscript review and editing. J.P.T.-A. conducted fieldwork, led stratigraphic description, and participated in manuscript review and editing. Y.P.V. conducted fieldwork, contributed to lithologic and sedimentologic descriptions, and participated in manuscript review and editing. B.C.G. contributed to study conception and design, supervised the project, contributed to carbon isotope and iron speciation data acquisition, interpreted results, acquired funding, and contributed to manuscript writing and editing. All authors discussed the results and approved the final manuscript.
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Communications Earth and Environment thanks the anonymous reviewers for their contribution to the peer review of this work. Primary Handling Editors: Jun Shen and Martina Grecequet. [A peer review file is available].
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McCabe, K.E., Marroquín, S.M., Caruthers, A.H. et al. Deoxygenation in the equatorial Panthalassan Ocean predated the end-Triassic mass extinction. Commun Earth Environ (2026). https://doi.org/10.1038/s43247-026-03362-w
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DOI: https://doi.org/10.1038/s43247-026-03362-w
