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Oyashirazu Formation (Chihara, 1955) Takeuchi et al., 2015

• Type locality: Oyashirazu seashore, Itoigawa city, Niigata prefecture
• Volcanic rocks
• Late Cretaceous (96.6, 89.7 Ma, K-Ar)
• Correlation: Ipponmatsuyama Formation

• Sedimentary facies: Terrestrial
• Lithofacies: Basaltic andesite tuff breccia, Garnet dacite lapilli tuff
• Lithofacies (Minor): Andesite - Dacite lava, Ryolitic tuff, Rhyolitic breccia

• Thickness: ca. 300 - 1,000 m or thicker
• Upper limit: Unconformity (Eboshiyama Formation)
• Lower limit: Conformity (Uchiyama Formation, Shiritakayama Formation), Unconformity (Kurobishiyama Formation, Tetori Group)

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

• Distribution: Oyashirazu seashore - Tonamigawa river - Kongogawa river, Itoigawa city, Niigata pref.; Sakaigawa river - Mizukamidani valley - Sasagawa river - Ogawa river, Asahi city, Shimoniikawa county, Toyama pref.; Aimoto, Unazuki, Kurobe city, Toyama pref.

• Takeuchi et al. (2017) Geology of the Tomari District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 121p. (in Japanese with English abstract 4p.)
• Takeuchi et al. (2015) Jour. Geol. Soc. Japan, vol.121, no.7, pp.193-216, DOI
• Takeuchi et al. (2015) Jour. Geol. Soc. Japan, vol.121, no.1, pp.1-17 DOI