Cretaceous-Tertiary boundary
Cre`ta´ceous-Tert´i`ar`y boun´da`ry
(krė`tā´shŭs)| n. | 1. | a thin layer of geologic deposits, of varying thickness in different parts of the world, found between the geological strata identified as Cretaceous and the strata above, identified as Tertiary; also, the time point or period marking the boundary between the Cretaceous and Tertiary periods. |