Resolving volcanic activity of 20MA ago with relative accuracy of 1 yr from tree rings of petrified woods
Resolving volcanic activity of 20MA ago with relative accuracy of 1 yr from tree rings of petrified woods
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从硅化木年轮中解析 20MA 前的火山活动，相对精度为 1 年
DOI：
10.1029/92gl01771
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发表时间：
1992
影响因子：
5.2
通讯作者：
Y. Fukao
中科院分区：
文献类型：
--
作者：
H. Kumagai;Y. Fukao
分析了石化木的树木年轮，以解决20 Ma前的火山活动，相对精度为1年。样品是那些在早中新世形成的火山角砾岩的火山岩和凝灰质湖沉积物在日本中部。野外观察表明，这些石化木是由火山爆发时喷出的火山角砾岩从生长地带走并包埋在其中的树木化石，我们用树木年代学方法测定了石化木最后年轮的相对年代。最后一个年轮的相对年份集中在17年，年轮宽度模式显示出一种异常的行为，类似于在被Mt.圣海伦。我们认为，石化木最后形成的树轮是火山喷发的记录，火山活动持续了17年，其中至少发生了5次喷发。关于活动期的高分辨率显示了树木年轮研究在地质过去调查火山活动的独特性。
Tree rings of petrified woods were analyzed to resolve a volcanic activity of 20 Ma ago with a relative accuracy of 1 yr. Samples are those in the volcanic breccia of the Early Miocene formation of volcaniclastic rocks and tuffaceous lake sediments in central Japan. Field observations indicate that these petrified woods are the fossils of the trees that were carried away from their growth sites with volcanic breccia ejected upon explosive eruption and included in it. Using a dendrochronological procedure we measured the relative years of the last rings of the petrified woods. The relative years of the last rings are concentrated in 17 yrs, where the ring-width patterns show an anomalous behavior similar to one observed in firs growing in the area devastated by Mt. St. Helens. We suggest that the last-formed tree ring of a petrified wood is a record of volcanic eruption and that the activity of volcano continued over a period of 17 yrs, in which eruption occurred at least five times. High resolution regarding the activity period demonstrates uniqueness of tree-ring study to investigate volcanism in the geologic past.