Elucidation of source volcanoes and depositional ages of the Maebashi and Tsukahara mudflows using Sr isotope ratios and 14C age

Abstract

Strontium isotopic ratios (87Sr/86Sr) of large volcanic blocks in the Maebashi mudflow deposit, which constitutes the basement of the Maebashi-Takasaki area in Gunma Prefecture, and the Tsukahara mudflow deposit, which constitutes the basement of the Saku-Karuizawa area in Nagano Prefecture, indicate that these mudflow deposits were brought by a failure event of Kurofu volcano, an initial stage volcanic edifice of Asama volcano. Furthermore, 14C ages of wood fragments buried in the deposits indicate that the mudflows were generated by the a failure event of Kurofu volcano during the last glacial period ca.27 ka cal BP (Sato et al., 2017, 2019, 2020, 2021, 2022) In this presentation, we present these results.