Calcareous sediments contain a high calcium carbonate content,
usually biologic in nature. They can be made of foraminifers (one celled
protist) or deposits from coral reef organisms. Coral reefs are usually
in shallower, warmer water like off of the southeast United States or
the Great Barrier Reef in Australia. Many corals as well as calcareous
algae make their skeleton from calcium carbonate.
Generally, calcareous deposits are biogenic in nature and represent