The study of widespread tephras in central Japan with special reference to the volcanic history of Norikura volcanic zone.

通过温度年代学，尤指来自遥远来源的广泛分布的温度层，如Aira和Ash层（缩写）。（AT）、Daisen Krayoshi浮石层（DKP）、Aso 4号火山灰层、Kikai-Tozurahara ash （K-Tz）等，将属于Norikura火山带的孤立火山产物相互对比，以研究Norikura火山带的火山演化。该地区的火山历史与第四纪构造运动有关，因为该地区的火山在N-S方向上排列良好，与日本中部第四纪最活跃的隆起轴之一重叠，并与伊藤川-静冈构造带的北部平行。火山年代学研究可以有效地将御竹火山和立山火山的年轻部分与它们自身众多的火山层联系起来，而火山地层学研究则不能有效地将Norikura火山、Yakedake火山和washibakumonotaira火山与前两个火山的老部分联系起来。Norikura火山带开始于0.7-0.6 Ma之前，根据放射性年龄，火山活动持续了大约0.3 Ma。在漫长的非活跃期之后，大约在0.1 Ma以前，较年轻的活动同时发生，在活动的早期阶段，每个火山喷发出的酸性物质最多。在御武火山和立山火山上，岩浆活动持续了大约3万年前。后来又谈到了Norikura和Yakedake火山。最近的潜水活动重复了火山带。为了完成这项研究，我们需要Norikura， Yakedake和Washiba-Kumonotaira火山产品的辐射年龄数据，因为它们似乎没有广泛的tephra层。

By means of tephrochronology, especially by widespread tephra layers from distant sources as Aira tn Ash layer(Abbr.:AT), Daisen Krayoshi Pumice layer(DKP), Volcanic ash layer of Aso 4, Kikai-Tozurahara Ash(K-Tz) and so on, the isolated volcanic products belonging to Norikura volcanic zone are correlated each other for the purpose of investigating volcanic evolution of the zone. The volcanic history of the zone is supposed to relate to quaternary tectonic movement, because the volcanoes of the zone align well on the N-S trend overllapping to one of the most active uplift-axis of central japan in quaternary time and paralleling to the northern part of the Itoigawa-Shizuoka tectonic zone.The tephrochronological research is effective in correlating the younger halves of Ontake and Tateyama volcanoes with their own numerous tephra layers, and tephra stratigraphy is not effective for Norikura, Yakedake and Washiba-Kumonotaira volcanoes and the older halves of the former two volcanoes.Norikura volcanic zone started about 0.7-0.6 Ma ago and the volcanism contnued for perhaps 0.3 ma based on radiometric age. After the long inactive period, the younger activity simultaneously took place about 0.1 Ma ago and the earlier stage of the activity erupted the most acidic products on each volcano. Magmatic activity lasted about 30,000 years ago on Ontake and Tateyama volcano. And continued more later on Norikura and Yakedake volcanoes. Recently the phreatic activities repeated the volcanic zone.To complete the study, we need the radiometric age data for the products on Norikura, Yakedake and Washiba-Kumonotaira volcanoes because they do not seem to have the extensive tephra layers.