Mass Extinction at the Cretaceous–Paleogene (K–Pg) Boundary

Abstract

One of the “Big Five” mass extinctions in the Phanerozoic Eon occurred at the Cretaceous–Paleogene (K–Pg) boundary (66.0 million years ago). The K–Pg mass extinction was triggered by a meteorite impact that produced a crater at Chicxulub on the Yucatan Peninsula, Mexico. The following environmental perturbations might have been induced by the Chicxulub impact and acted as the killing mechanisms for the K–Pg mass extinction: (1) sunlight shielding, (2) sulfuric and nitric acid rain, (3) CO2-induced global warming, (4) ultraviolet penetration, and (5) toxic effects of ground-level ozone. The details of these perturbation events are summarized in this chapter. Based on evidence in sedimentary rocks, we could confirm whether such perturbation events occurred or not. However, it was difficult to reconstruct quantitatively the magnitudes and durations for such perturbation events because the necessary time-resolved information (yearly to millennium-scale) is lacking.