Late Cretaceous followed by Palaeocene
Cretaceous–Paleogene mass extinction discovery
The Cretaceous–Paleogene extinction event was a large-scale mass extinction of animal and plant species in a geologically short period of time, approximately 66 million years ago (Ma). It is widely known as the K–T extinction event and is associated with a geological signature, usually a thin band dated to that time and found in various parts of the world, known as the Cretaceous–Paleogene boundary (K–T boundary). K is the traditional abbreviation for the Cretaceous Period derived from the German name Kreidezeit, and T is the abbreviation for the Tertiary Period (a historical term for the period of time now covered by the Paleogene and Neogene periods). The event marks the end of the Mesozoic Era and the beginning of the Cenozoic Era. "Tertiary" being no longer recognized as a formal time or rock unit by the International Commission on Stratigraphy, the K-T event is now called the Cretaceous—Paleogene (or K-Pg) extinction event by many researchers.