High-precision Radiocarbon Dating with Accelerator Mass Spectrometry and Calibration of Radiocarbon Ages

Abstract

High-resolution as well as high-precision age estimation is particularly important for Quaternary research to realize its main aim of better understanding of global environmental changes of the past and realistic prediction of the changes in the near future. Among several dating methods that are applicable to Quaternary samples, radiocarbon (14C) dating has been commonly used since its development in late 1940s.A new 14C detection technique, accelerator mass spectrometry (AMS), has been developed since 1977. The method directly detects and counts 14C atoms, instead of counting β-ray emitted in the decay of 14C, and therefore requires only a few mg of carbon for 14C measurements. Nowadays, AMS 14C dating is widely used and more than sixty AMS 14C facilities are in operation in the world. In Japan, eight facilities for AMS 14C dating have been in use since 2004.As one of the eight AMS 14C measurement systems in Japan, the Nagoya University AMS group has started routine 14C measurements with the firstly introduced Tandetron AMS system since 1983 and also with the secondly established Tandetron AMS since 1999. The second system has an excellent performance of the standard deviation (one sigma) of the 14C/12C ratios of around ±0.2% to ±0.4% (±17-±30 14C yrs) and that of the corresponding 13C/12C ratios of ±0.03% to ±0.07%, as are tested for HOxII targets. By using this AMS system, we are now trying to provide accurate ages to the Quaternary events. Briefly discussed in this article are, (1) a consistency test of the established IntCal98 and IntCal04 14C data sets with the 14C-concentration records in Japanese tree rings ; (2) programs of high accuracy and precision age estimation by 14C wiggle matching techniques for wood samples ; (3) investigations of 14C reservoir effect for marine samples from the Japanese Archipelago.