[S-GL44_2PM2] The Lower-Middle Pleistocene boundary of the Kazusa Group

[SGL44-11] Lower - Middle Pleistocene Boundary at Chiba Section and istribution situation of Byakubi Ash, central Japan

*Hideto KIMURA¹, Osamu KAZAOKA², Hisashi NIREI³ (1.Toho Chisui Co., Ltd. Kanto office, 2.Research Institude of Environmental Geology, Chiba, 3.International Union of Geological Science for Environmental Management(IUGS-GEM))

Keywords:Byakubi Ash, Kokumoto Formation middle-upper member, Yoro River, Chiba Section

The Byakubi Ash is distributed over the Ichihara City southern part and is located in the vicinity of a base of the middle-upper member of Kokumoto formation, Kazusa Group. Kokumoto formation is sorted four member by facies, is upper member (sandy alternation), middle-upper member (mussive mud), middle-lower member (sandy alternation) , and lower member (mussive mud). The Matsuyama / Brunhes chron boundary as the Lower - Middle Pleistocene Boundary is attracted by the lower base of the Byakubi Ash, it was confirmed that the Byakubi Ash was distributed from the Yoro River(Tabuchi) , Tabuchi River(Tabuchi), Nishi River(Tsukide), to the Koshikiya River (Koshikiya). The future follow-up survey comes to need a careful survey, but it is thought that it is to the important clue of the chase because the distribution situation of Ku2(Ku2B' and Ku2B) inserted between the high rank of the Buakubi Ash is considerably confirmed.