S1: Earth materials science in igneous processes (Special Session)

[S1P-03] Reexamination of the relationship between Sambe–Ukinuno and Sakate tephras based on refractive indices and chemistry of tephra components

*Seiji Maruyama¹ (1. KFT)

Keywords:Sambe–Ukinuno tephra, Sakate tephra, refractive index, chemical composition, tephra fall area

The Sambe–Ukinuno (SUk) tephra from Sambe volcano is dividied into the lowermost Uk-pfa, Md-fl, and uppermost Uk-fa. The Sakate tephra beds have been associated with the Md-fl. The refractive index of the volcanic glass shards of the Md-fl were lower than that of the Uk-pfa, because of the difference of the FeO contents rather than the SiO₂ contents. The Md-fl/Uk-fa (Sakate) widely distributes in the Chugoku and Kinki districts, whereas the Uk-pfa distributes in the southern Kinki and the eastern end of the Shikoku.