広島県世羅西町の段丘堆積層から見いだされたK-Ah火山灰とAT火山灰起源の火山ガラス

概要

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K-Ah volcanic ash and volcanic glasses derived from Aira-Tn volcanic ash were discovered from terrace deposits on the bank of Miharagawa river in Sera-Nishi Town. The terrace deposits are lithologically divided into the A and B formations in ascending order. The A formation consists of sand and gravel beds which is probably composed of both debris flow and flood deposits. Volcanic glasses derived from Aira-Tn volcanic ash are found in the sandy layer in the middle part of the formation. The B formation is mostly composed of peaty mud intercalated with thin lenticular beds of K-Ah volcanic ash. The volcanic ash and the volcanic glasses indicate that the A and B formations are late Pleistocene and Holocene in age, respectively. The fossil molar of Palaeoloxodon naumanni (Makiyama), which has been discovered at Tsuguchi in Sera Town, was probably obtained from the A formation.
広島大学学校教育学部の論文