Cretaceous period
白垩纪
地质
cretaceous period[ noun ]
from 135 million to 63 million years ago; end of the age of reptiles; appearance of modern insects and flowering plants
<noun.time>
Cretacic \Cre*tac"ic\
[Webster 1913 Suppl. +PJC]
{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, and at the end of which the dinosaurs died out.
See {Cretaceous}.
[1913 Webster +PJC]