Geology
Carbonate is found frequently in geologic settings and constitute an enormous carbon reservoir. Calcium carbonate occurs as aragonite and calcite. The carbonate minerals form the rock types: limestone, chalk, marble, travertine, tufa, and others.
In tropic settings, the waters are warm and clear. Corals are more abundant in this environment than towards the poles where the waters are cold. Calcium carbonate contributors, including plankton (such as coccoliths and planktic foraminifera), coralline algae, sponges, brachiopods, echinoderms, bryozoa and mollusks, are typically found in shallow water environments where sunlight and filterable food are more abundant. Cold-water carbonates do exist at higher latitudes but have a very slow growth rate. The calcification processes are changed by the ocean acidification.
Where the oceanic crust is subducted under a continental plate sediments will be carried down to warmer zones in the astenosphere and mesosphere where the calcium carbonate is decomposed to carbon dioxide which will give rise to explosive volcanic eruptions.
Read more about this topic: Calcium Carbonate