新潟県東頸城丘陵の千年テフラ層から大隅石の発見とその対比

概要

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The Chitose Tephra Bed (Ctp) in the Higashikubiki Hills of southwestern Niigata region was correlated to the Sug-a Tephra Bed in the Nishiyama and Hachikoku Oil Fields. The chemical composition of the glass shards of both tephras are coincident. In addition, the osumilite crystal was newly found from the Ctp tephra, which was so far reported from the Sug-a tephra. Based on this correlation, the age of the Ctp Tephra Bed was inferred to be around 2.4Ma. The Ctp Tephra Bed is intercalated in the upper Higashikawa Formation below the Naradate Formation. Thus, lower shallow marine environment (the Higashikawa Formation) was transformed into the upper shallow marine environment (the Naradate Formation) in around 2.4-2.3Ma through the processes of the progradation in the Niigata sedimentary basin.
新潟大学の論文