Japan Geoscience Union Meeting 2019

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[J] Poster

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS20] Mountain Science

Mon. May 27, 2019 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Keisuke Suzuki(Department of Environmental Sciences, Faculty of Science, Shinshu University), Yoshihiko Kariya(Department of Environmental Geography, Senshu University), Akihiko SASAKI(Department of Geography and Environmental Studies, Kokushikan University), Chiyuki Narama(Niigata University, Department of Science)

[MIS20-P05] Probable glacier detritus found at downstream site of the Yokoo moraines in the northern Japanese Alps: its geological characteristics and implications

*Manami Ishibashi1, Yoshihiko Kariya2, Kuniyasu Mokudai3 (1.Undergraduate Senshu Univ., 2.Senshu Univ., 3.Japan Geo serivice Inc.)

Keywords:glaciations, the Last Glacial age, late Pleistocene, till, Japanese Alps

Around the upper reach of Azusa River in the northern Japanese Alps, the lowest position of a glacier snout during the late Pleistocene was known as the Yokoo-Iwagoya moraines (ca. 1700 m ASL). We revisited this widely-accepted concept of paleoglaciations in the Japanese Alps and newly found poorly-sorted angular to subangular rock clasts from the site lower than Yokoo-Iwagoya moraines (ca. 1400 m longitudinal and 50 m vertical). Rock clasts are composed of Quaternary igneous rocks that are never distributed around Yokoo. We concluded that those rock clasts were transported by a valley glacier from the higher slopes of Mount Yari-Hotaka Massif around 2800–3000 m ASL. Depositional ages of the clasts are still unknown but the Marine Isotope Stage 4 was probable.