A study on accurate age determination of volcanic eruptions by high-precision 140 dating and a wiggle matching analysison charred wood from volcanic deposits

2001年在白头山火山采集了6个木材样本，经仔细检查，发现2个烧焦的树干有树皮。其中较大的一个有102个年轮，被用于^<14>C年代测定。年轮被分成82个样本。由于年轮狭窄，外20个年轮每两年划分一次。各年轮从21^<st>到92^<和>分开。92^<以内的年轮和>以内的年轮破碎，无法分离。我们分析了82个样本中的35个：大约每三个年轮。木炭样品经AAA处理后，按常规方法转化为石墨。用名古屋大学的HVEE Tandetron测量了^<14>C, ^<13>C和^<12>C。通过摆动匹配，将所得数据与INTCAL98 ^<14>C校准数据进行比较。我们得到了一个清晰的峰的概率分布，对应于最外层两个环的混合物生长的时间最可能在公元935年，误差为+8和-5年。这说明白头山火山的喷发与公元926年渤海国的灭亡没有关系。其次，按照时间顺序对郁陵岛的麻风进行了研究。一般认为U-Oki tephra在日本约9.3-9.6 kaBP形成。郁陵岛已识别出U1、U2、U3、U4层，其层位高于AT层（2.5 kaBP）。2002年和2003年在郁陵岛进行的调查中，从U2（烧焦的木材）、U3（有机土壤）、U4（烧焦的树枝和有机土壤）采集了^<14>C定年的碳样本。^<14>的C年龄，U2为5 kaBP， U3为7.5-8.0 kaBP， U4为10-12 kaBP。这些结果表明，日本的U-Oki tephra对应于U4。这确实是一个新发现，因为U-Oki tephra被认为与U2相对应。

Six wood samples were collected from Baitoushan Volcano in 2001 and two charred wood trunks were detected to have barks by careful inspection. The larger one of the two, with 102 annual rings, was used for ^<14>C dating. The annual rings were divided into 82 samples. The outer 20 annual rings were divided every two years because of narrow annual rings. From 21^<st> to 92^<nd> each annual ring was separated. Annual rings inner than 92^<nd> ring were broken and could not be separated. We have analyzed 35 samples out of 82 : approximately every three annual rings. The charcoal samples were processed by AAA treatments and converted to graphite in a routine method. The ^<14>C, ^<13>C and ^<12>C were measured with a HVEE Tandetron at Nagoya University. The obtained dates were compared with the INTCAL98 ^<14>C calibration data by wiggle matching. We obtained a probability distribution of one clear peak that corresponded to the time when the mixture of the outermost two rings was grown most probably in 935 cal AD, with errors of +8 and -5 years. This results implies that the eruption of Baitoushan Volcano had no relation with the fall of the Bo-hai State in AD926.ext, tephras from the Ulleung Island were studies chronologically. The U-Oki tephra is commonly accepted to have deposited in Japan at around 9.3-9.6 kaBP. The tephra layers U1, U2, U3 and U4 have been recognized on the Ulleung Island and their horizons were upper than the AT tephra (2.5 kaBP). During the survey at the Ulleung Island in 2002 and 2003, carbon samples for ^<14>C dating were collected from U2 (charred wood), U3 (organic soil) and U4 (charred twigs and organic soil). ^<14>C ages obtained for these layers were 5 kaBP for U2, 7.5-8.0 kaBP for U3 and 10-12 kaBP for U4. These results imply that the U-Oki tephra in Japan corresponds to U4. This is a really new finding, because the U-Oki tephra has been believed to correspond to U2.