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

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.