The presence of the Iridium indicates that an asteroid impact occurred at the boundary. Iridium is a rare metal on earth but is abundant in asteroids. The presence of high levels of iridium in any layer of rock is a strong indication of an asteroid impact. The Cretaceous-Paleogene boundary signifies the extinction of the dinosaurs. The asteroid was found to have impacted the planet just off the coast of Mexico on the Yucatan Penninsula.