1:45 PM - 3:15 PM
[O03-P59] The formation age and environment of the Tubo River outcrop,Seki in Gifu prefecture, Central Japan.
Keywords:Late Pleistocene, Ontake volcano, Stream deposits
In the research concluded until last year, the outcrop of Tubo River that flows through Shimokurachi in Seki city Gifu prefecture is stream deposit by the pumice Old Kiso River that erupted at Mt.Ontake about 60 to 90 thousand years ago.
This study, the pumice of this outcrop and several pumice collected in the standard outcrop of Mt.Ontake tephra in Ina city, Nagano prefecture are compared from the characteristics of heavy mineral composition and Hypersthene. As a result, this outcrop included pumice called On Pm-Ⅰ,On-In, On-Mt. Also, From the deposition structure of this outcrop, the abandonment of the diversion toward the Seki city of the Old Kiso River is considered to have occurred about 60 to 55 thousand years ago, integrated with other previous research.
This study, the pumice of this outcrop and several pumice collected in the standard outcrop of Mt.Ontake tephra in Ina city, Nagano prefecture are compared from the characteristics of heavy mineral composition and Hypersthene. As a result, this outcrop included pumice called On Pm-Ⅰ,On-In, On-Mt. Also, From the deposition structure of this outcrop, the abandonment of the diversion toward the Seki city of the Old Kiso River is considered to have occurred about 60 to 55 thousand years ago, integrated with other previous research.