2021 Volume 130 Issue 3 Pages 429-443
A tephra layer from Lake Suigetsu tentatively correlated with the Sambe–Koyahara tephra from Sambe volcano was correlated based on the geochemistry of a Sambe–Koyahara tephra sample obtained near the source volcano and the petrographic properties of samples of the Sambe–Koyahara and Daisen–Kamogaoka tephras. The petrographic and geochemical properties of the Suigetsu tephra suggest that it should be correlated with the Daisen–Kamogaoka tephra. The eruptive volume of the Daisen–Kamogaoka tephra was estimated to be small, and it could hardly reach Lake Suigetsu. However, considering the absence of no other Daisen tephra which could reach Lake Suigetsu in the same eruption activity and the thinness of the correlated Suigetsu tephra layer in the core sample, there is a possibility that the correlated Suigetsu sample corresponds to a very small amount of the Daisen–Kamogaoka tephra which could reach Lake Suigetsu. The elemental patterns of the Sambe–Koyahara sample and the Suigetsu samples correlated with the Sambe tephras indicate that the chemistry of the magma of Sambe volcano changed from non-adakitic to adakitic between stages II (Sambe–Koyahara) and IV (the Sambe–Ukinuno tephra), with the transitional adakitic Sambe–Ikeda tephra being erupted during stage III.
