瑞浪層群明世層産貝類におけるストロンチウム同位体年代の追加記録

抄録

Additional strontium isotope ratio (87Sr/86Sr) of molluscs including Crenomytilus grayanus (Dunker), from the Akeyo Formation of the Mizunami Group in Mizunami City, Gifu Prefecture, central Japan are determined. The strontium isotopic ages suggest that the Crenomytilus grayanus-bearing horizon (most-lower part of the Yamanouchi Member, Akeyo Formation) has been deposited at ca. 17.8 Ma. In addition, upper part of the Kubohara Facies (middle part of the Maki Member), Iwamura Group has been deposited at same age of the Yamanouchi Member.