When worlds collide: the end-Cretaceous global crisis

The paper reviews the debate which has been conducted during the past decade over the end-Cretaceous extinction and the controversy over its cause. The evidence for the extinction is examined, together with geological and geochemical evidence for a bolide impact, focusing on the problems that beset researchers seeking definitive answers to the question whether the end-Cretaceous extinction was a global crisis emanating from a single bolide impact. Possible impact sites discussed include the Manson structure in Iowa, and the Chicxulub feature on the Yucatan peninsula in Mexico. An impact scenario is recreated and a sequence of events postulated to link the various lines of evidence. -G.E.Hodgson