LARGE-BODY IMPACT AND EXTINCTION IN THE PHANEROZOIC

The kill curve for Phanerozoic marine species is used to investigate large-body impact as a cause of species extinction. Current estimates of Phanerozoic impact rates are combined with the kill curve to produce an impact-kill curve, which predicts extinction levels from crater diameter, on the working assumption that impacts are responsible for all "pulsed" extinctions. By definition, pulsed extinction includes the approximately 60% of Phanerozoic extinctions that occurred in short-lived events having extinction rates greater than 5%. The resulting impact-kill curve is credible, thus justifying more thorough testing of the impact-extinction hypothesis. Such testing is possible but requires an exhaustive analysis of radiometric dating of Phanerozoic impact events.