K–T boundaryK–T boundary

The K–T boundary is a geological signature, usually a thin band, dated to 65.5 ± 0.3 Ma (million years) ago.[1] K is the traditional abbreviation for the Cretaceous period, and T is the abbreviation for the Tertiary period. The boundary marks the end of the Mesozoic era and the beginning of the Cenozoic era, and is associated with the Cretaceous–Tertiary extinction event, a mass extinction.[2] With "Tertiary" being discouraged as a formal time or rock unit by the International Commission on Stratigraphy, the K–T extinction event is now called the Cretaceous–Paleogene (or K–Pg) event by many researchers.[3]


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