The final geological period of the Mesozoic Era, dating from approximately 145 to 66 million years ago, named after the extensive chalk deposits found in Europe during this time.

chalk; a soft, white, porous limestone consisting mainly of calcium carbonate

The sequence of rock layers formed during the Cretaceous Period, positioned between the Jurassic and Paleogene systems.

Cretaceous, the geological period between approximately 145 and 66 million years ago

(bound form) of or relating to the Cretaceous period; specifically referring to the geologic period from about 145 to 66 million years ago