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The internationally recommended INTCAL98 calibration data set is widely used for calibration of radiocarbon (^<14>C) age to calendar date. It is believed that the INTCAL98 data set can represent the general variation of ^<14>C concentrations for the period from 11850 cal BP to present, based on tree ring chronology. To test the applicability of the INTCAL 98 data set to Japanese samples, we have measured ^<14>C ages for a submerged wood trunk of Japanese cypress tree collected from Ashinoko Lake, Hakone-cho, Kanagawa Prefecture, Japan. Routine ^<14>C dating was conducted with a Tandetron accelerator mass spectrometer at the Center for Chronological Research, Nagoya University. Tree rings of the wood sample covered from AD 61 to AD 180, for a span of 120 years, as were dated by a dendrochronological analysis at Nara Cultural Properties Research Institute. Neighboring ten annual rings were combined together to produce 12 samples from the wood. The ^<14>C ages of nine samples were compared with those of the INTCAL98 data set at relevant calendar years, and an obvious shift of ^<14>C ages for the cypress wood was observed towards the dates older than those by the INTCAL98 data set, by about 30 ^<14>C years. This trend coincides with the results for a bogwood (Japanese cedar) unearthed at Hakone-cho, Kanagawa Prefecture. The sources of such age discrepancies maybe related to a local geological event, such as dilution of atmospheric ^<14>CO_2 concentration with volcanic ^<14>C-free CO_2 emitted intermittently from Hakone volcano. Further analyses are required to test this speculation and explain these results in detail.
タンデトロン加速器質量分析計業績報告 Summaries of Researches Using AMS 2003 (平成15)年度
名古屋大学加速器質量分析計業績報告書 15 206-214, 2004-03