Did the Puchezh-Katunki Impact Trigger an Extinction?

Abstract

The 80 km diameter Puchezh-Katunki impact crater is the only one of thesix largest known Phanerozoic craters that has not been previouslyconsidered as a factor in a biotic extinction event. The age of impactis currently regarded as Bajocian (Middle Jurassic), on the basis ofpalynostratigraphy of crater lake sediments, but there is no significantextinction in the Bajocian. Earlier K-Ar age determinations ofimpactites compared with a current Jurassic time scale permit thateither the end-Triassic or the Early Jurassic (Pliensbachian-Toarcian)extinction was coeval with the Puchezh-Katunki crater. Thestratigraphical and paleontological record contains clues that suggestthat an impact may have occurred at these horizons. The age of thePuchezh-Katunki crater needs reevaluation through Ar-40/Ar-39 dating ofimpact rocks and/or revision of the palynology of the oldest craterfill. A definitive age determination will help constrain the impact-killcurve.