Cretaceous–Paleogene boundary events

The Cretaceous–Paleogene (K–Pg) boundary is recognized as one of the major catastrophic perturbations which affected the marine and terrestrial ecosystems and changed the earth's history and the path of evolution forever. Following this, the story of the K–Pg boundary has fascinated everyone interested in the history of life and death on our planet. In the quarter century since the publication of the seminal Alvarez et al. paper in Science in 1980, a large number of studies of the Cretaceous–Paleogene (K–Pg) boundary have been published. These papers typically have been interdisciplinary, and have involved collaborations of specialists in quite varied areas. The two topical sessions “Mass extinctions and other large ecosystem perturbations: extraterrestrial and terrestrial causes” and “K/T boundary events” at the 32nd International Geological Congress held in Florence in August 2004 that focused on mass extinctions and environmental perturbations, and on the K–Pg boundary itself, provide an opportunity to bring together some of the newest results pertaining to the K–Pg mass extinction and its causes. This special issue includes the most relevant contributions and allows these new results to be presented in the context of the history of the link between K and Pg boundary events and an extraterrestrial impact, and the possible ramifications of the impact hypothesis for the study of mass extinctions and the subdivisions of geologic time in general.