Question

What is the original source of the carbon that is present within carbonate deposits such as limestone?

Answer 1

Limestone is a sedimentary type of  rock composed largely of the mineral calcite (calcium carbonate: CaCO3).

Limestones often contain variable amounts of silica in the form of chert or flint, as well as varying amounts of clay, silt and sand as disseminations, nodules, or layers within the rock.

Here we can conclude that the original source of carbon that is present within carbonate deposits like limestone is calcium carbonate.

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