Massive perturbations to atmospheric sulfur in the aftermath of the Chicxulub impact

Christopher Junium*, Aubrey Lea Zerkle*, James Witts, Linda Ivany, Thomas Yancey, Chengjie Liu, Mark Claire

*Corresponding author for this work

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Sulfate aerosols have long been implicated as a primary forcing agent of climate change and mass extinction in the aftermath of the end-Cretaceous Chicxulub bolide impact. However, uncertainty remains regarding the quantity, residence time, and degree to which impact-derived sulfur transited the stratosphere, where its climatic impact would have been maximized. Here, we present evidence of mass-independent fractionation of sulfur isotopes (S-MIF) preserved in Chicxulub impact ejecta materials deposited in a marine environment in the Gulf Coastal Plain of North America. The mass anomalous sulfur is present in Cretaceous–Paleogene event deposits but also extends into Early Paleogene sediments. These measurements cannot be explained by mass conservation effects or thermochemical sulfate reduction and therefore require sulfur-bearing gases in an atmosphere substantially different from the modern. Our data cannot discriminate between potential source reaction(s) that produced the S-MIF, but stratospheric photolysis of SO2 derived from the target rock or carbonyl sulfide produced by biomass burning are the most parsimonious explanations. Given that the ultimate fate of both of these gases is oxidation to sulfate aerosols, our data provide direct evidence for a long hypothesized primary role for sulfate aerosols in the postimpact winter and global mass extinction.
Original languageEnglish
Article numbere2119194119
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number14
Early online date21 Mar 2022
Publication statusPublished - 5 Apr 2022


  • K-Pg extinction
  • Sulfur isotopes
  • Mass-independent fractionation
  • Mass extinction
  • Sulfur cycle


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