香川県丸亀平野における上部更新統および完新統の層序

概要

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The Marugame Plain, located in the northeastern part of the Shikoku Island, is one of the largest plains around the Seto Inland Sea. The late Quaternary sediments in the plain are divided into Daisokugawa, Dokigawa and Marugame Formations. Dokigawa Formation is subdivided into three members: the lower, the middle and the upper members of Pleistocene. The upper member consists mainly of mud deposit around 95ka to 26ka. The overlying Marugame Formation is also subdivided into five members; Utazu sand and mud, Tadotsu sandy gravel, Marugame Port sandy gravel, Shioyacho sand, and Harada-cho mud members. The volcanic ash named "Marugame Port 2" which can be correlated to Aira-Tn volcanic ash(AT), was found in the upper member of Dokigawa Formation. Another volcanic ash named "Utazu-hama 2" which can be correlated to Kikai-Akahoya volcanic ash(K-Ah), was found in Marugame Formation.