| Co-Investigator(Kenkyū-buntansha) |
MIURA Taichi Applied Research Laboratory, Assistant Professor, 放射線科学センター, 助教授 (80209717)
SUZUKI Takenori Applied Research Laboratory, Professor, 放射線科学センター, 教授 (40162961)
KONDO Kenjiro Applied Research Laboratory, Professor, 共通研究施設, 教授 (20004434)
OKI Yuicih Applied Research Laboratory, Assistant Professor, 原子炉実験所, 助教授 (40204094)
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| Research Abstract |
Although the universal calibration curves have been widely used for radiocarbon dating of Japanese samples and should be suitable for practical use, it is necessary to establish its basis of correctness. To improve this situation we have performed precise 14C calibration using dendrochronologically dated tree-rings of cedars and cypresses. We focused on the ages between 350 BC and AD 900, in particular the prehistoric era called the Yayoi Period and the proto-historic era known as the Kofun Period in the history of Japan.
The tree ring samples used in this study are specimens from Japan Cedar (Sugi) trees, including bog-woods from Hakone (HK series, 240BC〜AD200) and Miyata-Mura, Nagano Pref.(MT, AD330〜AD630) and timbers excavated at the Hotta-no-Saku Site, Akita Pref. (AH1, AD690〜AD800 ; AH3, AD660〜AD900). The dendro-dates were determined by comparison of the standardized ring patterns with the master chronology at the Nara National Cultural Properties Research Institute.
The specimens were cut into decadal pieces, pulverized to fine fiber tips, processed by a conventional acid-base-acid treatment, and finally extracted as cellulose. The cellulose was oxidized into carbon dioxides, which were then purified and converted into graphite. For most of the samples 14C was measured by AMS at Gronningen Univercity.
The result shows that they are generally in good agreements with the INTCAL98 data, which are based on the European and North American woods. However, we have to reserve a possibility that several 14C data may show a small deviation from INTCAL98 at certain years. Wiggle-matching gives almost exactly the dendro-dates, and the differences being only a few years. Good agreements are also found for cypress (Hinoki) tree-rings from the Ikegami-Sone Site, Osaka Pref. These results confirm for the first time the correctness of using INTCAL98 for Japanese samples. The results will be presented at International Radiocarbon Conference in Israel (June, 2000).
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