The Iridium anomaly refers to a significant layer of sediment found in the geologic record that contains elevated levels of the rare element iridium. This layer is primarily associated with the boundary between the Cretaceous and Paleogene periods, approximately 66 million years ago. The iridium spike is notable because iridium is relatively rare on Earth's surface but more abundant in meteorites.
The discovery of this anomaly was pivotal in supporting the hypothesis that a large asteroid or comet impact contributed to the mass extinction event that led to the demise of the dinosaurs and many other species at the end of the Cretaceous period. The most widely accepted impact site associated with this event is the Chicxulub crater in the Yucatán Peninsula in Mexico.
The iridium anomaly has been instrumental in advancing the understanding of Earth's geological history and the role of extraterrestrial events in shaping life on our planet.