image: This is the Cretaceous-Palaeogene boundary at Geulhemmerberg in the Netherlands. view more
Credit: Michael J. Henehan
Researchers report evidence of global environmental changes during the Cretaceous-Paleogene (K-Pg) mass extinction. The K-Pg mass extinction, which occurred 66 million years ago, coincides with the Chicxulub asteroid impact and intense volcanic activity in the Deccan Traps. Little empirical evidence exists for the specific mechanism by which either of these factors could have contributed to the mass extinction. Michael Henehan and colleagues measured boron isotope ratios, a proxy for ocean pH, in fossil marine microorganisms from before, during, and after the K-Pg boundary. The data indicate that a rapid pulse of ocean surface acidification occurred immediately following the Chicxulub impact, suggesting a mechanism for mass extinction in the oceans. This pulse was followed by a rapid pH rebound and overshoot caused by the selective extinction of calcifying marine organisms and prompted a major disruption of the global carbon cycle. Earth system model simulations suggested that ocean carbon isotope and pH patterns observed after the K-Pg boundary were consistent with a 50% reduction in global marine primary productivity. The authors suggest that the reduction in global primary productivity lasted up to 40,000 years. However, even after productivity began to recover, the ecological aftermath of extinction continued to affect Earth's carbon cycle through inefficient carbon export from the surface to the deep sea. Furthermore, the absence of prolonged ocean surface acidification suggests that increased volcanism played a minor role, if any, in driving the mass extinction, according to the authors.
Article #19-05989: "Rapid ocean acidification and protracted Earth system recovery followed the end-Cretaceous Chicxulub impact," by Michael J. Henehan et al.
MEDIA CONTACT: Michael J. Henehan, GFZ German Research Centre for Geosciences, Potsdam, GERMANY; tel: +49-331-288-28600, +49-175-6607867; e-mail: michael.henehan@gfz-potsdam.de; Pincelli M. Hull, Yale University, New Haven, CT; tel: 858-220-3359; e-mail: pincelli.hull@yale.edu
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Journal
Proceedings of the National Academy of Sciences