The majority of carbon sequestration at the Earth’s surface occurs in marine continental margin settings within fine-grained sediments whose mineral properties are a function of continental climatic conditions.

The low 13C/12C ratio in some Neoproterozoic carbonates is considered to be evidence of carbon cycle perturbations unique to the Precambrian. Here, all published oxygen and carbon isotope data for Neoproterozoic marine carbonates are compiled.

Many aspects of the carbon cycle can be assessed from temporal changes in the 13C/12C ratio of oceanic bicarbonate. 13C/12C can temporarily rise when large amounts of 13C-depleted photosynthetic organic matter are buried at enhanced rates, and can decrease if phytomass is rapidly oxidized2 or if low 13C is rapidly released from methane clathrates.