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Ipponmatsuyama Formation (Chihara et al., 1979) Shiraishi, 1992

• Type locality: Mount Ipponmatsu, Kotaki, Itoigawa city, Niigata prefecture
• Coherent formation
• Late Cretaceous (66.4 Ma, FT)
• Correlation: Oyashirazu Formation

• Sedimentary facies: Terrestrial
• Lithofacies (Upper): Hornblende biotite dacite tuff breccia
• Lithofacies (Lower): Hornblende andesite - Pyroxene andesite tuff breccia, Tuff

• Thickness: ca. 350 m
• Upper limit: Unconformity (Ishizaka Formation)
• Lower limit: Unconformity (Akahageyama Formation, Oeyama Ophiolite)

------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown

• Distribution: Mount Ipponmatsuyama - Mount Anamiyama - Hiyodori pond - Mushikawa river, Itoigawa city, Niigata pref.; Kitaotari, Otari city, Kitaazumi county, Nagano pref.

• Takeuchi et al. (2015) Jour. Geol. Soc. Japan, vol.121, no.7, pp.193-216, DOI
• Nagamori et al. (2010) Geology of the Kotaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 130p. (in Japanese with English abstract 4p.)
• Machi and Ishiwatari (2010) Jour. Geol. Soc. Japan, vol.116, no.6, pp.293-308 DOI
• Takeuchi et al. (2010) Jour. Geol. Soc. Japan, vol.116, Supplement, pp.123-142 DOI