D defs.my
Entry 2 senses Webster, 1913

Cretaceous

/(krē̇*tā"shŭs)/ · Cre·ta·ceous · IPA /kɹəˈteɪ.ʃəs/
01 a. Having the qualities of chalk; abounding with chalk; chalky; as, cretaceous rocks and formations. See Chalk.
  1. 1.
    Having the qualities of chalk; abounding with chalk; chalky; as, cretaceous rocks and formations. See Chalk. See: Chalk
  2. 2.
    Of, pertaining to, or designating, the period of time following the Jurassic and preceding the Paleogene. See Cretaceous period below.(Geol.)
Phrases & compounds
Cretaceous acid — an old name for carbonic acid.
Cretaceous formation — the series of strata of various kinds, including beds of chalk, green sand, etc., formed in the Cretaceous period; -- called also the chalk formation. See the Diagram under Geology.
Cretaceous period — the time in the latter part of the Mesozoic age during which the Cretaceous formation was deposited.