Cretaceous-Tertiary boundary /(krē̇*tā"shŭs)/

Cre·ta·ceous-Tert·i·ar·y boun·da·ry

Cretaceous-Tertiary boundary

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.