JpGU-AGU Joint Meeting 2017

Presentation information

[JJ] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS13] [JJ] Environmental changes in mountainous area

Thu. May 25, 2017 10:45 AM - 12:15 PM 301B (International Conference Hall 3F)

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

11:30 AM - 11:45 AM

[MIS13-16] Development of paleolakes related to landslide activities in the late Pleistocene epoch on the eastern foot of Mount Kushigata, the Koma Mountains in central Japan

*Ryoga Ohta1, Yoshihiko Kariya2 (1.Undergraduate at Senshu University , 2.Department of Environmental Geography, Senshu University )

Keywords:Landslide, Lacustrine sediments, Tephrochronology, Pollen analysis, On-Pm1 tephra, On-In tephra

A north-south strike elongated depression 5 km long and 1-1.5 km wide is present on the eastern piedmont of Mount Kushigata, west of the kofu basin in central Japan. This depression is filled by older landslide deposits formed in the middle Pleistocene epoch. The older landslide deposits are covered with thick lacustrine sediments consisting of peat and silt, bearing On-Pm1 (100 ka) and On-In (90 ka) pumice layers. Stratigraphy, petrography, lithofacies, and the result of pollen analysis of the lacustrine sediments reveal the historical development of paleolakes on the older landslide bodies. The lacustrine sediments are seen at several outcrop localities with different altitudes in the depression, suggesting the presence of several lakes or ponds. The water bodies were formed initially during from Marine Isotope Stage 6 to 5d (185-110 ka) and had persisted for ten thousand or a few tens of thousands years. The paleolakes were buried by the younger landslide deposits after 90 ka. The historical development of the depression and paleolakes would be related to large-scale gravitatiolal slope deformation of Mount Kushigata as well as the displacement of Ichinose fault located between Mount Kushigata and the Kofu basin.