Isotopic signature, of carbon

The isotopic fractionation in carbonates mirrors the relative amount of organic carbon buried. It is generally assumed that the source carbon, from vulcanism (the so-called mantle carbon) has an isotopic value of approximately 5%c. As mass balance must constrain the isotopic signatures of carbonate carbon and organic carbon with the mantle carbon, then... 

Larsen, C.S., Schoeninger, M.J., van der Merwe, N.J., Moore, K.M. and Lee-Thorp, J. 1992 Carbon and nitrogen isotopic signatures of human dietary change in the Georgia Bight. American Journal of Physical Anthropology 89 197-214. 

When plants are consumed as food by herbivorous animals, the isotopic signatures in the plants are passed on to the consumers. Therefore, provided the isotopic signatures of C3 and C4 plants are known, determining the isotopie signatures in the tissues of herbivorous animals enables one to determine the relative amounts of C3 and C4 plants that the animals consumed as food, and to reconstruct their diets. Moreover, since carnivorous and omnivorous animals, including humans, feed on herbivorous animals as well as on plants, determining the isotopic signatures of the isotopes of carbon in tissues of ancient animals and humans makes it possible to elucidate the components of their diets. 

Paradis, S., Turner, W.A., Coniglio, M., Wilson, N. Nelson, J.L. 2006. Stable and radiogenic isotopic signatures of mineralized Devonian carbonates of the Northern Rocky Mountains and the Western Canada Sedimentary Basin. In Hannigan, P.K. (ed) Potential for carbonate-hosted lead-zinc Mississippi Valley-type mineralization in northern Alberta and southern Northwest Territories Geoscience Contributions,... 

Table 3.1 Average carbon (6 3C) and nitrogen (6 5 ) isotope signature of HMWDOM isolated from several different sites in the Atlantic Ocean. Pacific Ocean, and the Gulf of Mexico...

Silfer J. A. (1991) Stable carbon and nitrogen isotope signatures of amino acids as molecular probes in geologic systems. PhD Thesis, University of Oklahoma. 

More subtly, the isotopic signatures of photosynthesis in inorganic sediment are also valuable. Rubisco depletes the environment of Hence, inorganic carbonate is enriched in if rubisco operates on a planetary scale. Carbon dioxide emitted from the mantle is about 5%o to... 

Jahnke L. L., Summons R. E., Hope J. M., and Des Marais D. J. (1999) Carbon isotopic fractionation in lipids from metha-notrophic bacteria II. The effects of physiology and environmental parameters on the biosynthesis and isotopic signatures of biomarkers. Geochim. Cosmochim. Acta 63, 79-93. 

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