1. of, relating to, or containing chalk or a chalky substance
Usage: technical/geological
2. of or relating to the Cretaceous Period, the final period of the Mesozoic Era, lasting from about 145 to 66 million years ago
Usage: geology; often capitalized when referring to the geological period

Examples

• The cliffs along the coast are composed of cretaceous deposits.
• Cretaceous rocks are rich in fossils from the age of dinosaurs.
• The Cretaceous Period ended with a mass extinction event.
• Cretaceous sediments contain abundant marine fossils.
• These cretaceous formations date back over 100 million years.