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

Invalid synonym: Oyashirazu Volcanic Rocks

• Type locality: Oyashirazu seashore, Itoigawa city, Niigata prefecture; Sakai river, Asahi city, Toyama prefecture
• Coherent formation
• Late Cretaceous (96.6, 89.7 Ma, K-Ar)
• Correlation: Ipponmatsuyama Formation

• Sedimentary facies: Terrestrial
• Lithofacies (Main): Andesitic tuff breccia, Andesitic tuff
• Lithofacies (Minor): Andesite lava, Ryolitic tuff, Rhyolitic breccia

• Thickness: 1,000 m or thicker
• Upper limit: Unconformity (Sasakawa Welded Tuff Formation)
• Lower limit: Unconformity (Kurobishiyama Formation), Conformity (Uchiyama Formation, Shiritakayama Formation)

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

• Distribution: Oyashirazu seashore, Itoigawa city, Niigata pref.; Sakai river, Asahi city, Toyama pref.

• 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