Definition

1. Adjective:

   • Relating to the Cretaceous period: Of, relating to, or denoting the third and final period of the Mesozoic Era, characterized by the dominance of dinosaurs and the first appearance of flowering plants.
   • Abounding in chalk: Composed of or containing chalk, a soft, white, porous sedimentary rock.

2. Noun (Proper noun, often capitalized):

   • The Cretaceous period: The geological period from approximately 145 to 66 million years ago, following the Jurassic and ending with the extinction of the dinosaurs.

Usage Examples

• Adjective:

  • The Cretaceous rocks in this region are rich in fossils. (Describes rocks from that geological era.)
  • The cliff face is composed of cretaceous chalk deposits. (Describes the rock's composition.)

• Noun:

  • The Cretaceous ended with a massive asteroid impact. (Refers to the time period itself.)
  • Many iconic dinosaurs, like Tyrannosaurus rex, lived during the Cretaceous.* (Specifies the era of existence.)

Advanced Usage

• "Cretaceous-Paleogene (K-Pg) boundary": The geological marker, often a thin layer of clay, that defines the end of the Cretaceous Period and the beginning of the Paleogene Period, associated with a mass extinction event.
  • Scientists study the K-Pg boundary to understand the dinosaur extinction.

Variants and Related Words

• Cretaceous Period (n): The full name for the geological period.
• Cretaceous System (n): The stratigraphic system of rocks deposited during the Cretaceous Period.

Synonyms

• Chalky (adj): Resembling or containing chalk. (This is a synonym primarily for the "abounding in chalk" sense, not the time period sense.)
• Mesozoic (adj): Relating to the entire era that includes the Triassic, Jurassic, and Cretaceous periods. (A broader category.)

Related Phrases

• Late/Early Cretaceous: Subdivisions of the Cretaceous Period.
  • The Late Cretaceous saw the evolution of advanced horned dinosaurs.
• Cretaceous fauna/flora: The animals and plants that lived during the Cretaceous Period.

Adjective

1. of or relating to or denoting the third period of the Mesozoic era
2. abounding in chalk

Noun

1. from 135 million to 63 million years ago; end of the age of reptiles; appearance of modern insects and flowering plants