jessica simpson dating football player - Fractionation for dating

Fractionation during the geochemical transfer of carbon in nature produces variation in the equilibrium distribution of the isotopes of carbon (12C, 13C and 14C).

Craig (1953) first identified that certain biochemical processes alter the equilibrium between the carbon isotopes.

The radiocarbon dating method is based on the fact that radiocarbon is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen.

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Some processes, such as photosynthesis for instance, favour one isotope over another, so after photosynthesis, the isotope C13 is depleted by 1.8% in comparison to its natural ratios in the atmosphere (Harkness, 1979).

Conversly the inorganic carbon dissolved in the oceans is generally 0.7% enriched in 13C relative to atmospheric carbon dioxide.

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In order to explore the implications of this possibility, the standard formulae for correcting radiocarbon dates for fractionation effects are rederived, but without making any of the usual assumptions or approximations.

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