Discovery of K-Ah Volcanic Ash and Volcanic Glasses Derived from Aira-Tn Volcanic Ash from Terrace Deposits in Sera-Nishi Town, Hiroshima, Southwest Japan
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.