Determining the time of year when the Chicxulub Impactor fell.
The end-Cretaceous extinction event wiped out 76% of known species on Earth, but was strangely selective in the way it did so. The non-Avian Dinosaurs were wiped out, as were the Pterosaurs, most Marine Reptiles, Ammonites, Belemnites, and Rudists, amongst other groups. The extinction event is believed to have been caused by a bolide impacting the Gulf of Mexico near the Yucatan Peninsula, creating the Chicxulub Impact Crater. Evidence of the direct effects of this impact, including impact glass fallout, large-scale forest fires and tsunamis, have been found in areas of North America more than 3500 km from the impact site, and the subsequent events are thought to have included a global climatic breakdown which lasted for thousands of years.