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Fractionation Corrections in Radiocarbon Dating

Published online by Cambridge University Press:  18 July 2016

T M L Wigley
Affiliation:
Climatic Research Unit, University of East Anglia Norwich NR4 7TJ, U K
A B Muller
Affiliation:
Laboratory of Isotope Geochemistry, University of Arizona Tucson, Arizona 85721
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Abstract

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Recent experimental work has suggested that the relative fractionation of 14C to 13C may differ from the accepted value of b = 2. 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. A generalized dating equation is derived (where ASN and AON are normalized sample and standard activities, β is a factor which reflects changes in atmospheric 13C and 14C content, {RST(o)/RST}b accounts for post-depositional changes in sample 13C ratio, and tcal is calendar age in years before ad 1950. The errors in calculated ages which might arise from different b values are estimated and shown to be small relative to other dating uncertainties. The effect of b ≠ 2 may be important in the calibration of radiocarbon dates using tree-ring samples of known age. A theoretical analysis suggests that b ≠ 2 effects may result in a correlation between age anomaly (ie, the difference between radiocarbon age and calendar age) and sample 13C data. However, an analysis of published data reveals no meaningful correlation. This result, while not eliminating the possibility that b ≠ 2, highlights its unimportance even in this high-precision application of radiocarbon dating.

Type
Research Article
Copyright
Copyright © The American Journal of Science 

References

Barbetti, Mike, 1980, Geomagnetic strength over the last 50,000 years and changes in atmospheric 14C concentration: Emerging trends, in Minze, Stiuver and Renee, Kra, eds, Internatl radiocarbon conf, 10th, Proc: Radiocarbon, v 22, no. 2, p 192199.CrossRefGoogle Scholar
Bigeleisen, J and Mayer, M G, 1947, Calculation of equilibrium constants for isotopic exchange reactions: Jour Chem Physics, v 15, p 261267.CrossRefGoogle Scholar
Michael, Bruns, Münnich, K O, and Becker, Bernd, 1980, Natural radiocarbon variations from AD 200 to 800, in Stuiver, Minze and Kra, Renee, eds, Internatl radiocarbon conf, 10th, Proc: Radiocarbon, v 22, no. 2, p 273277.Google Scholar
Craig, Harmon, 1954, Carbon-13 in plants and the relationships between carbon-13 and carbon-14 in nature: Jour Geol, v 62, p 115149.CrossRefGoogle Scholar
Eddy, J A, 1977, Climate and the changing sun: Climatic Change, v 1, p 173190.CrossRefGoogle Scholar
Galimov, E M, 1978, Paper, Internatl geol, cosmochronol, and isotope geol conf, 4th: Snowmass, Colorado.Google Scholar
Ingerson, E and Pearson, F J Jr, 1964, Estimation of age and rate of motion of ground water by the 14C method, in Recent researches in the fields of hydrosphere, atmosphere and nuclear chemistry: Maruzen, Japan, p 263283.Google Scholar
de Jong, A F M and Mook, W G, 1980, Medium-term atmospheric 14C variations, in Stuiver, Minze and Kra, Renee, eds, Internatl radiocarbon conf, 10th, Proc: Radiocarbon, v 22, no. 2, p 267272.CrossRefGoogle Scholar
Keeling, C D, Mook, W G, and Tans, P P, 1979, Recent trends in the 13C/12C ratio of atmospheric carbon dioxide: Nature, v 277, p 121123.CrossRefGoogle Scholar
Michael, H N and Ralph, E K, 1974, University of Pennsylvania radiocarbon dates XVI: Radiocarbon, v 16, p. 198218.CrossRefGoogle Scholar
Radnell, C J, 1980, The isotopic fractionation of 14C and 13C relative to 12C in Slater, E A and Tate, J O, eds, Internatl, symposium on Archaeometry and Archaeol, Prospection, 16th, Proc, p 360392.Google Scholar
Richet, P, Bottinga, Y, and Javoy, M, 1977, A review of hydrogen, carbon, nitrogen, oxygen, sulphur and chlorine stable isotope fractionation among gaseous molecules: Ann Rev Earth Planetary Sci, v 5, p 65110.CrossRefGoogle Scholar
Stuiver, Minze, 1978, Atmospheric carbon dioxide and carbon reservoir changes: Science, v 199, p 253258.CrossRefGoogle ScholarPubMed
Stuiver, Minze, 1980, Solar variability and climatic change during the current millennium: Nature, v 286, p 868871.CrossRefGoogle Scholar
Stuiver, Minze and Polach, H A, 1977, Reporting of 14C data: Radiocarbon v 19, p 355363.CrossRefGoogle Scholar
Stuiver, Minze and Quay, P D, 1980, Changes in atmospheric carbon-14 attributed to a variable sun: Science, v 207, p 1119.CrossRefGoogle ScholarPubMed
Stuiver, Minze and Robinson, S W, 1974, University of Washington GEOSECS North Atlantic carbon-14 results: Earth Planetary Sci Letters, v 23, p 8790.CrossRefGoogle Scholar
Suess, H E, 1978, La Jolla measurements of radiocarbon in tree-ring dated wood: Radiocarbon, v 20, p 118.CrossRefGoogle Scholar
Suess, H E, 1980, The radiocarbon record in tree rings of the last 8000 years, in Stuiver, Minze and Kra, Renee, eds, Internatl radiocarbon conf, 10th, Proc: Radiocarbon, v 22, no. 2, p 200209.CrossRefGoogle Scholar
Thiemens, M H and Clayton, R N, 1979, A search for isotopic nuclear spin effects (abs): Meteoritics, v 14, p 545547.Google Scholar
Turro, N J and Traeutler, B, 1978, Magnetic isotope and magnetic field effects on chemical reactions. Sunlight and soap for the efficient separation of 13C and 12C isotopes: Jour Am Chem Soc, v 100, p 74327434.CrossRefGoogle Scholar
Urey, H C, 1947, The thermodynamic properties of isotopic substances: Jour Chem Soc. p 562581.CrossRefGoogle Scholar
Wigley, T M L, Plummer, L N, and Pearson, F J, 1978, Mass transfer and carbon isotope evolution in natural water systems: Geochim et Cosmochim Acta, v 42, p 11171139.CrossRefGoogle Scholar
Williams, L D, Wigley, T M L, and Kelly, P M, 1980, Climatic trends at high northern latitudes during the last 4000 years compared with 14C fluctuations, in Sun and climate: Toulouse, France, C N E S, p 1120.Google Scholar