Assessing the contributions of comet impact and volcanism toward the climate perturbations of the Paleocene-Eocene Thermal Maximum

The Paleocene–Eocene Thermal Maximum (PETM) is marked by a prominent negative carbon-isotope excursion (CIE), reflecting the injection of thousands of gigatons of isotopically-light carbon into the atmosphere. The sources of the isotopically-light carbon remain poorly constrained. Utilizing a multiproxy geochemical analysis (osmium isotopes, mercury, sulfur, platinum group elements) of two Paleocene–Eocene boundary records, we present evidence that a comet impact and major volcanic activity likely contributed to the environmental perturbations during the Paleocene–Eocene interval. Additionally, Earth System Model simulations indicate that stratospheric sulfate aerosols, commensurate with the impact magnitude, were likely to have caused transient cooling and reduced precipitation.