\Cre*ta"ceous\ (kr[-e]*t[=a]"sh[u^]s), a. [L.
cretaceus, fr. creta chalk. See {Crayon}.]
Having the qualities of chalk; abounding with chalk; chalky;
as, cretaceous rocks and formations. See {Chalk}.
{Cretaceous acid}, an old name for carbonic acid.
{Cretaceous formation} (Geol.), 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} (Geol.), the time in the latter part of
   the Mesozoic age during which the Cretaceous formation was
   deposited.

\Cre*ta"ceous\, a. Also Cretacic \Cre*tac"ic\ (Geol.)
Of, pertaining to, or designating, the period of time
following the Jurassic and preceding the Eocene.