Which term describes marine organisms that produce calcareous plates contributing to carbonate sediments?

• A. Foraminiferan
• B. Evaporite
• C. Coccolithophore
• D. Diatom

Answer: (C)

Calcium carbonate sediments in the ocean are largely built by microscopic calcareous organisms that produce plates. The term that describes marine organisms producing calcareous plates is coccolithophore. These tiny, photosynthetic algae secrete numerous calcium carbonate plates called coccoliths that coat the cell. When they die, these plates accumulate as carbonate sediment, contributing to deposits like coccolith ooze and even chalk in the geological record. While foraminiferans also produce calcium carbonate shells, their structure is a shell rather than plates; diatoms form silica shells, not carbonate; evaporites are chemical minerals formed from evaporating water, not biological. So the best match for organisms with calcareous plates contributing to carbonate sediments is the coccolithophore.