Description and Correlation of the Nagate Tephra Found in the Terrace Deposits at the Southern Foot of Asan Range in Tokushima Prefecture, Southwestern Japan

摘要

We discovered a tephra in the terrace depos- its at the southern foot of Asan Range in Tokushima Prefecture, southwestern Japan, and named it the Nagate tephra. The Nagate tephra is brown to gray-white in color and is composed of sand-and silt-sized grains that in- clude many phenocrysts. The Nagate tephra is compared with Aso-4 tephra in terms of pe- trography, refractive index of volcanic glass, and chemical composition of pyroxene.