Mass extinction caused by extraterrestrial impact: Why did it occur only at the Cretaceous/Paleogene boundary?

Abstract

In the past 30 years, many researchers have investigated the relationship between extraterrestrial impacts and mass extinction events of the Phanerozoic. Nevertheless, such a relationship has only been confirmed for the Cretaceous/Paleogene (K.Pg) boudary at 65.5 Ma. Here, we review existing geological evidence for impact events during the Phanerozoic, recent advances in studies of impact frequency, and the distribution of crater size on the Moon. We conclude that the magnitude of the K/Pg boundary impact was exceptionally large among Phanerozoic events, and may have been a once in 500-1000 Myr event. The mechanism of extinction at the K/Pg boundary associated with extraterrestrial impact, remains poorly understood, in part because the size and formation process of the impact crater (Chicxulub Crater) are poorly constrained. The recovery of drillcore from within the crater is required to clarify the mechanism of the K/Pg mass extinction.