A study of determining the tree-ring age with a precision of one year by 14C wiggle matching

本研究旨在探讨利用AMS对考古遗址或地质沉积物中出土的木材年轮进行14C定年，并应用14C摆动匹配，以一年的精度确定年轮年龄的可能性。我们首先测量了尽可能多的单个年轮的14C年龄，这些年轮是从生长在鹿儿岛的Yaku岛和奈良的Muroji寺的日本雪松中分离出来的。样品树木的年代学提前测定了年代。对来自Muroji树的61个年轮（AD1617-1739）、来自yaku岛树的173个年轮（AD1413-1615）和78个年轮（AD881-1072）进行了14C测年，并与国际通用的IntCa104 14C年龄校准数据进行了比较。14C年龄在测量误差范围内是一致的，但日本树木的14C年龄有比各自年轮的IntCa104数据更老的趋势。接下来，来自Muroji树的55个年轮（AD1631-1739）和来自yaku岛树的142个年轮（AD1413-1554）与IntCa104数据进行了抖动匹配。匹配结果显示，Muroji树的14c测定年龄与树木测定年龄完美吻合，不确定性为+/-2年（95%置信度）。对于雅库岛的树，14c测定的年龄比树突测定的年龄要老4年，有+/-2年的不确定性。这清楚地表明，如果对样本树进行更多的年轮测定，那么通过摆动匹配来估计树木的年龄是可能的，其精度约为一年。我们还尝试用摆动匹配的方法对考古和地质木材样品的最外层年轮进行定年，并得出结论，这种方法比仅对树木最外层年轮进行14C定年的普通方法要准确得多。

This research aims to investigate the possibility of determining the age of annual ring for a wood sample excavated from archeological sites or geological sediments with a precision of one year, by 14C dating of their annual rings with AMS and applying 14C wiggle-matching. We first measured 14C ages of individual annual rings as many as possible that were separated from Japanese cedar trees grown in Yaku Island, Kagoshima, and at Muroji temple, Nara, Japan. The sample trees were dated dendrochronologically in advance.61 annual rings (AD1617-1739) from the Muroji tree, 173 (AD1413-1615) and 78 rings (AD881-1072) from the Yaku-Island tree were 14C dated and their age values are compared with respective 14C values from the internationally accepted IntCa104 14C-age calibration data. The 14C ages were consistent with one another within measurement errors, but a tendency that 14C ages of Japanese trees were older than IntCa104 data for respective annual rings.Next, 55 annual rings (AD1631-1739) from the Muroji tree and 142 rings (AD1413-1554) from the Yaku-Island tree were wiggle-matched to the IntCa104 data. The matching yielded a perfect coincidence of 14C-determined age to dendro-dated one with +/-2 year uncertainty (95% confidence) for the Muroji tree. For the Yaku-island tree, 14C-determined age was older by 4 years than the dendro-dated one with +/-2 year uncertainty. It is clearly suggested that age estimation of a tree is possible with a precision of about one year by wiggle matching if a larger number of annual rings will be dated for the sample tree.We also tried to date the outermost ring of archeological and geological wood samples by wiggle matching, and could conclude that a far better accuracy is obtained by this method than by the ordinary method of 14C dating of only the outermost annual ring of the woods.