十和田八戸火砕流堆積物中の樹木年輪を用いた14Cウイグル・マッチング年代

概要

The Towada-Hachinohe pyroclastic flow is a non-welding dacitic to rhyolitic pyroclastic flow deposit (ca. 40 km3 in volume). The tephra (To-H) associated with this eruption is correlated with the volcanic glass NEEM1502.60m (22 grains) from the Greenland ice core, which has been dated to 15.7 ± 0.2 ka b2k (2σ). In a nearby area, a buried forest lies directly beneath this tephra and radiocarbon (14C) dates of approximately 13 ka BP have been obtained. In addition, van der Plicht et al. (2012) obtained 16,534–16,204 cal BP (2σ) by wigglematching 34 14C ages from an approximately 350-year-old buried tree to the calibration dataset IntCal09. We matched them to the IntCal20 and obtain 15,775–15,710 cal BP (2σ) using the computer program Oxcal ver. 4.4. We measured ten 14C ages of buried tree (99 annual rings) collected from the pyroclastic flow deposits (40 °31'57.8"N, 141°11'30.8"E) with accelerator mass spectrometry (AMS) and obtained 14C ages of 13,338–13,137 BP. These 14C ages were matched with IntCal20 and yielded 15,886–15,774 cal BP (2σ). Assuming that the To-H age from the ice cores is the true (reliable) age, the matching ages with the IntCal09 are more than 500 years old. Comparing the matching results of matching with the IntCal20, a larger number of annual rings and measurement data, provides a narrower range of calendar date (i.e., higher precision).

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