Used for

• Boundary, Cretaceous-Paleogene
• Boundary, Cretaceous-Tertiary
• Cretaceous-Tertiary boundary
• Cretaceous-Tertiary transition
• K-Pg boundary
• K-T boundary
• Paleogene-Cretaceous boundary
• Tertiary-Cretaceous boundary
• Transition, Cretaceous-Tertiary