||Identification of three Early Pleistocene tephras in and around the west part of the Musashino Upland, Tokyo, Northeast Japan
Suzuki, Takehiko ,
Nakajima, Eri ,
Kawashima, Shinichi ,
Kawai, MasabumiNakayama, Toshio
Geographical Reports of Tokyo Metropolitan University
134 , 2016 , Department of Geography, Tokyo Metropolitan University
In and around the west part of the Musashino Upland, southwest of the Kanto Tectonic Basin, Ob4b-4 (1.62 Ma), Ob4b-1 (1.63 Ma), and Ob3 (1.71-1.78 Ma) tephras in the Kazusa Group, early Quaternary strata, were identified by using characteristic properties such as chemical composition of volcanic glass shards and titanomagnetite, and refractive indices of glass shards, hornblende, cummingtonite, and orthopyroxene. Changes in altitudes of Ob4b-1 identified in four cores and at three outcrops together with those by previous studies indicate geological structure of the Kazusa Group, revealing a gentle northeastward sloping with a gradient of 15/1000 and a prominent discontinuity of the strata along the Tachikawa Fault Zone.