Quaternary environment, dating and analytical techniques

Qian, Y., Wu, Z., Kanai, Y., Terashima, S., Okumura, K., and Matsuhisa, Y. (1993) The study of constituents for sand minerals in the Taklimakan Desert.Proc. Japan-China Int'l Symposium on the study of the mechanism of desertification, 201-209.

Koji Okumura [1995] Refinement of radiocarbon dates for higher precision and accuracy. The Quaternary Research (Tokyo), 191-194.

[abstract] Correction and calibration of radiocarbon dates are indispensable procedures for accurate and precise age estimation. The most significant factors for correction and calibration are reservoir effect, isotopic fractionation, and secular variation in atmospheric 14C concentration. The correction of the reservoir effect is enabled by carbon-cycle modeling or by dating pre-atomic age marine sample of known age. The effect of isotopic fractionation that ranges 0 to -50 permill d13C or up to 400 14C years. This effect is easily corrected through d13C measurement using mass spectorometer. Accumulated 14C dates of dendrochronologically dated tree ring samples made it possible to calibrate the deviation caused by 14C concentration variation. Now versatile correction and calibration programs for personal computer are available. High precision 14C dating will be meaningful through understanding all calibration and correction methods.

Figure 1 Dendrochronological calibration curve of recent 3000 years. The curve is based on the data set 93_TREE1, which is compiled from the data reported in Radiocarbon vol. 35 no.1 for CalibETH (Niklaus, 1991).

Figure 2 Examples of dendrochronological calibration. Gaussian probability distribution of radiocarbon age is transformed into non-Gaussian probability distribution (middle and bottom) using the calibration curve (top). The shape of the calibration curve and the magnitude of original standard deviation (1s) constrain the result of calibration. All plotted data are based on numerical output of CalibETH (Niklaus, 1991).

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E-mail: kojiok@ipc.hiroshima-u.ac.jp

26 October 1996