Question

Coral reefs that are preserved as sedimentary rocks are classified as

Answer 1

The answer is; fossil

Fossil is defined as any dead organism ( or its trace or impression) of a past geological time that is naturally preserved in the earth in geological features such as rocks, bogs, and etcetera. Coral reef is  no exception because it is considered a living organism.  It is composed of colonies of coral polyps and algae that secrete a carbon carbonate skeleton.