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Hachimoriyama Formation (Tamiya et al., 1970) Furukawa et al., 2018

• Type locality: Summit of Mount Hachimori, Yonezawa city, Yamagata prefecture
• Volcanic rocks
• Pliocene (4.9 - 4.3, 3.4 Ma, K-Ar, 2.2 Ma, FT)
• Contemporaneous heterotopic facies: Otoge Formation
• Correlation: Saitsu Pyroclastic Flow Deposit

• Sedimentary facies: Pyroclastic flow deposit
• Lithofacies: Clinopyroxene hornblende biotite dacite, Biotite dacite
• Lithofacies: Pumiceous lapilli tuff

• Thickness: 1,000 m or thicker
• Lower limit: Unconformity (Itaya Formation)

• Distribution: Mount Hachimori - Maekawa river - Motokoya river - Okoya river, Yonezawa city, Yamagata pref.; Kanizawa, Inawashiro city, Yama county, Fukushima pref.
• Tephra: Saitsu Pyroclastic Flow Deposit

• Furukawa et al. (2018) Geology of the Azuma Yama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 74p. (in Japanese with English abstract 3p.)