Unusually high concentrations of the element iridium found worldwide in sediments that were deposited at the Cretaceous-Tertiary boundary (K-T boundary
) 65 million years ago. Since iridium is more abundant in extraterrestrial material, its presence is thought to be evidence for a large meteorite impact that may have caused the extinction of the dinosaurs and other life at the end of the Cretaceous.
© RM 2014. Helicon Publishing is division of RM.