Greater than 50% of the world's oil reserves are found in carbonate rocks. Temperature, sea level, and sedimentation rates play an important role in the production of carbonate materials. The majority are created in warm and clear waters as reefs and shelf materials. Carbonate deposits can form in a variety of settings along the shelf margins. The production of carbonate materials can vary greatly, forming reefs, algal mats and muds, and ooid shoals.