Rapid ocean acidification and protracted Earth system recovery followed the end-Cretaceous Chicxulub impact

1,2Michael J. Henehan,3,4Andy Ridgwell,1,5Ellen Thomas,1Shuang Zhang,6Laia Alegret,7Daniela N. Schmidt,8James W. B. Rae,9,10James D. Witts,9Neil H. Landman,11Sarah E. Greene,12Brian T. Huber,1James R. Super,1Noah J. Planavsky,1Pincelli M. Hull
Proceedings of the National Academy of Sciences of teh United States of America (PNAS) (in Press) Link to to Article [https://doi.org/10.1073/pnas.1905989116]
1Department of Geology & Geophysics, Yale University, New Haven, CT 06520;
2Section 3.3, Deutsches GeoForschungsZentrum GFZ, 14473 Potsdam, Germany;
3School of Geographical Sciences, Bristol University, Bristol BS8 1SS, United Kingdom;
4Department of Earth Sciences, University of California, Riverside, CA 92521;
5Department of Earth and Environmental Sciences, Wesleyan University, Middletown, CT 06459;
6Instituto Universitario de Investigación en Ciencias Ambientales de Aragón, Departamento de Ciencias de la Tierra, Universidad de Zaragoza, 50009 Zaragoza, Spain;
7School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, United Kingdom;
8School of Earth & Environmental Sciences, University of St. Andrews, St. Andrews KY16 9AL, United Kingdom;
9Division of Paleontology, American Museum of Natural History, New York, NY 10024;
10Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131;
11School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom;
12Department of Paleobiology, Smithsonian Institution, Washington, DC 20560

Mass extinction at the Cretaceous–Paleogene (K-Pg) boundary coincides with the Chicxulub bolide impact and also falls within the broader time frame of Deccan trap emplacement. Critically, though, empirical evidence as to how either of these factors could have driven observed extinction patterns and carbon cycle perturbations is still lacking. Here, using boron isotopes in foraminifera, we document a geologically rapid surface-ocean pH drop following the Chicxulub impact, supporting impact-induced ocean acidification as a mechanism for ecological collapse in the marine realm. Subsequently, surface water pH rebounded sharply with the extinction of marine calcifiers and the associated imbalance in the global carbon cycle. Our reconstructed water-column pH gradients, combined with Earth system modeling, indicate that a partial ∼50% reduction in global marine primary productivity is sufficient to explain observed marine carbon isotope patterns at the K-Pg, due to the underlying action of the solubility pump. While primary productivity recovered within a few tens of thousands of years, inefficiency in carbon export to the deep sea lasted much longer. This phased recovery scenario reconciles competing hypotheses previously put forward to explain the K-Pg carbon isotope records, and explains both spatially variable patterns of change in marine productivity across the event and a lack of extinction at the deep sea floor. In sum, we provide insights into the drivers of the last mass extinction, the recovery of marine carbon cycling in a postextinction world, and the way in which marine life imprints its isotopic signal onto the geological record.


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