Ash beds in the deep-sea core sampled at the base of the Koshu Seamount in the Shikoku Basin, Philippine Sea

Abstract

Four ash beds have been found in the 485cm core obtained at the base of the Koshu Seamount in the Shikoku Basin. In order to make clear the petrographic features of these ash beds, the heavy mineral contents and the refractive indices of the main constituent minerals have been examined. Based on the petrographic studies, the presence of the Aira ash from the Aira caldera volcano in southern Kyshu is discussed. These petrographic data do not indicate the presence of any Aira ash in this particular core.