Dictionary

K–T boundary

noun

Definition of K-T BOUNDARY

:  the transition between the Cretaceous and Tertiary periods of geologic time characterized by a mass extinction of many forms of life including the dinosaurs; also :  a geologic stratum marking this boundary
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Origin of K-T BOUNDARY

K (alternative for C as abbreviation for Cretaceous) + Tertiary
First Known Use: 1983

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