中期更新世テフラ, Ng-1火山灰の広域性の検討

抄録

This paper presents an example of the correlation of Early to Middle Pleistocene tephras in Japan. The Ng-1 Ash, intercalated in the Middle Pleistocene Negoya Formation, and tephras which have similar characteristics from various localities in central Japan have been examined. The Ng-1 Ash consists of glass shards, feldspar, quartz and heavy minerals (biotite, amphibole and orthopyroxene). Some tephras at other localities are correlated with the Ng-1 Ash, based on their chemical compositions and refractive indices, their horizons and other characteristics. The age of the Ng-1 Ash is estimated to be 0.3 Ma, and it appears that the source volcano is located in the northern Japan Alps. Investigations covering a wide area are needed to verify both the age and the location determinations.