Two large meteorite impacts at the Cretaceous-Paleogene boundary

The end Cretaceous mass exinction has been attributed to a single asteroid impact at Chicxulub on the Yucatan peninsula, Mexico. The discovery of a second smaller crater at Boltysh in the Ukraine with a similar age has raised the possibility that a shower of asteroids or comets impacted Earth close to the K/Pg boundary. Here we present palynological and d13C evidence from crater fill sediments in the Boltysh impact crater. Our analyses demonstrate that a post-impact flora formed on the ejecta layer, was in turn devastated by the K/Pg events. The sequence of floral recovery from the K/Pg event is directly comparable with that in mid North America. We conclude that the Boltysh crater pre-dated Chicxulub by as little as 2,000 years, a timescale that constrains the likely origin of the bodies that formed the two known K/Pg craters.