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.
Links:
[1] http://admin.indiaenvironmentportal.org.in/feature-article/late-precambrian-greening-earth
[2] http://admin.indiaenvironmentportal.org.in/category/author/l-paul-knauth
[3] http://admin.indiaenvironmentportal.org.in/category/author/martin-j-kennedy
[4] http://admin.indiaenvironmentportal.org.in/category/journal/nature
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/limestone
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/sedimentation
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/carbon-dioxide
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/climate-change
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/climate-science
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/carbon-sequestration
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/flora