The intermediate claystone layer contains 1000 times more iridium than the upper and lower layers. It is the boundary between Cretaceous and Tertiary Periods. The rock is from Wyoming, USA.This image of Mexico's Yucatán Peninsula show a subtle, but unmistakable, indication of the Chicxulub impact crater. Most scientists agree that this impact was the main cause of the Cretaceous-Tertiary extinction.Deccan Plateau
The Cretaceous–Tertiaryextinction event, now called the Cretaceous–Palaeogene extinction event,[1] was about 65.5 million years ago.[2] It may be called the K/T extinction event or K/Pg event for short. This is the famous event which killed most of the dinosaurs at the end of the Cretaceous period.
↑Fortey R (1999). Life: A natural history of the first four billion years of life on Earth. Vintage. pp. 238–260.
↑With "Tertiary" being discouraged as a formal time or rock unit by the International Commission on Stratigraphy, the K/T event is now called the Cretaceous–Palaeogene extinction event by many researchers. Gradstein F, Ogg J, Smith A. A geologic time scale 2004.{{cite book}}: CS1 maint: multiple names: authors list (link)