Study of Widespread Tephras Derived from Northeast Japan

日本东北部广泛分布的火山灰的研究

基本信息

批准号：
13680105
负责人：
SUZUKI Takehiko
金额：
$ 1.41万
依托单位：
Tokyo Metropolitan University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

The purpose of this study is to recognize widespread tephras derived from Northeast Japan for providing time-markers to the precise Quaternary chronology. Research was done by collecting many samples in distal and proximal areas and describing characteristic properties of them. Results are shown as follows.(1) Two ignimbrites were newly identified in Hakkoda area. Stratigraphy of these ignimbrites and Hakkoda 1^<st> and 2^<nd> pyroclastic flow deposits previously identified was established and characteristic properties of these were determined. Moreover, paleo-magnetic investigation revealed that Hakkoda 1^<st> pyroclastic flow deposits have normal polarity and Hakkoda 0 and Ose pyroclastic flow deposits have reverse polarity. This result is concordant with the correlation of the distal tephra associated with Hakkoda 1^<st> pyroclastic flow.(2) A widespread tephra named Seiganji-Toga Tephra (0.6-0.7 Ma) previously recognized in Boso peninsula is newly recognized in Northeast Japan, and this tephra derived from Kyushu will be a favorable time-marker in this study. Chemical composition of rare earth element in volcanic glass shards shows reliability of the correlation of this tephra from Kyushu to Boso and Oga peninsulas.(3) To investigate widespread tephras from Northeast Japan, comparisons of chemical compositions among tephras including vitric tephras layers and ignimbrites in Northeast Japan were carried out. No vitric tephra correlative to ignimbrites in Hokkaido was found. It is clarified that several properties of Ose pyroclastic flow deposits in Hakkoda area and Ashino pyroclastic flow deposits in Shirakawa area are similar to those of U8 tephra in Boso peninsula. It is difficult to judge which is the tephra correlative to U8 tephra. This problem is left for a further study.

这项研究的目的是认识到来自日本东北部的广泛的tep虫，以便为精确的第四纪时间顺序提供时间标记。研究是通过收集远端和近端区域的许多样本并描述其特征性特性来完成的。结果如下所示。（1）在Hakkoda区域新鉴定出两个点火膜。这些Ignimbrites和Hakkoda 1^<ST>和2^<nd> pyroclastic流量沉积物的地层学已确定，并确定了这些流量的特性。此外，古磁研究表明，hakoda 1^<st> pyoclastic流量沉积物具有正常的极性，而Hakkoda 0和OSE Pyroclastic Flow沉积物具有反极性。该结果与远端tephra与Hakkoda 1^<ST> Pyroclastic流的相关性一致。（2）一个名为Seiganji-Toga Tephra（0.6-0.7 MA）的广泛的Tephra（先前在Boso Peninsula中在日本东北部的Boso Peninsula中认可的），这是在日本东北部的新认可的，并从此tereable中得到了研究。火山玻璃碎片中稀土元素的化学组成显示了该tephra的相关性的可靠性。在北海道中未发现与Ignimbrites相关的植物。可以澄清说，Shirakawa地区Hakkoda地区的OSE火山碎屑流沉积物和Ashino Pyroclastic流量沉积物的几种特性与Boso Peninsula的U8 Tephra相似。很难判断哪个与U8 Tephra的Tephra相关。此问题将进行进一步研究。