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The Accuracy of Radiocarbon Dates

Published online by Cambridge University Press:  02 January 2015

W. F. Libby
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The first test of the accuracy of dates obtained by the radiocarbon technique was made by determining whether dates so obtained agreed with the historical dates for materials of known age (n. 1). The validity of the radiocarbon method continues to be an important question, especially in the light of the numerous results that have been accumulated and the greater precision of the technique during the past few years (n. 2).

The radiocarbon content of the biosphere depends on three supposedly independent geophysical quantities: (i) the average cosmic ray intensity over a period of 8000 years (the average life of radiocarbon) as measured in our solar system but outside the earth's magnetic field (n. 1); (ii) the magnitude (but not the orientation, because of the relatively rapid mixing over the earth's surface) of the magnetic field in the vicinity of the earth, averaged over the same period (n. 1,3); and (iii) the degree of mixing of the oceans during the same period (n. 1). The question of the accuracy of radiocarbon dates therefore is of interest to geophysicists in general as well as to the archaeologists, geologists and historians who use the dates.

Previous workers in this area (n. 1, 2) have reported some discrepancies, and it is the purpose here to consider the matter further.

Type
Research Article
Information
Antiquity , Volume 37 , Issue 147 , September 1963 , pp. 213 - 219
Copyright
Copyright © Antiquity Publications Ltd 1963

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References

(1) W. F. Libby, Radiocarbon Dating (Univ. of Chicago Press, Chicago, ed. 2, 1955).

(2) H. de Vries, Proc. Amsterdam Acad. Sci., B61, 1 (1958); W. S. Broecker, E. A. Olson, J. Bird, Nature, 183, 1582 (1959); E. K. Ralph, Am. J. Sci. Radiocarbon Suppl., 1, 45 (1959); H. E. Suess, ‘Secular Changes in the Concentration of Atmospheric Radiocarbon’, Natl. Acad. Sci.—Natl. Res. Council Publ. No. 845-90 (1960); P. E. Damon, paper presented at the 5th Radiocarbon Dating Conference, Cambridge University, 1962.

(3) W. Elsasser, E. P. Ney, J. R. Winkler, Nature, 178, 1226 (1956).

(4) Am. J. Sci. Radiocarbon Suppl., 1 (1959).

(5) I. E. S. Edwards, private communication.

(6) H. Godwin, Nature, 195, 984 (1962); ibid., p. 943.

(7) Most of the data in Fig. 4 were presented by Elizabeth Ralph at the 5th Radiocarbon Dating Conference. The Arizona data were presented at the same conference by Paul E. Damon. I wish to thank both authors for permission to use these data.

(8) W. S. Glock and S. Agerter, Endeavour, 22, 9 (1963). These authors show that more than one ring can form in one year, as had been suggested earlier.

(9) M. Honda and J. R. Arnold, Geochim. Cosmochim. Acta, 22 (1961); T. P. Kohman and W. D. Ehman, paper presented at the International Conference on Radioisotopes, UNESCO, Paris, 1957; O. A. Schaeffer, R. W. Stoenner, R. Davis, Jr., Radioisotopes in the Physical Sciences and Industry (International Atomic Energy Agency, Vienna, 1962), vol. 1, p. 3; J. Geiss, H. Oeschger, U. Schwarz, lecture in Varenna (Italy) Marine Biological Institute summer course on cosmic rays, 1961 ; M. Honda, J. P. Shedlovsky, J. R. Arnold, Geochim. Cosmochim, Acta, 22, 133 (1961); J. R. Arnold and H. Honda, ‘The record of cosmic ray intensity in the meteorites’, in preparation.

(10) E. Bullard, private communication.

(11) G. J. F. MacDonald, private communication.

(12) H. E. Suess and W. Broecker, private communications.

(13) The work discussed in this article was supported in part by the National Science Foundation (grant G-14287).