Which term denotes microscopic algae with silica-based shells that contribute to siliceous ooze?

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

Answer: (D)

Siliceous ooze forms from biogenic silica produced by microscopic algae. Diatoms build their shells from silica, creating intricate frustules. When these diatoms die, their silica shells sink and accumulate on the ocean floor, producing siliceous ooze. Coccolithophores and foraminiferans use calcium carbonate to form their shells, which leads to calcareous ooze, while evaporites form from mineral precipitation due to evaporation. So, the algae with silica-based shells that contribute to siliceous ooze are diatoms.