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Ako Welded Tuff (Yamada et al., 1971) Collaborative Research Group for the Nohi Rhyolite, 1976

Invalid synonym: Ako Formation

• Type locality: Ako, Shirakawa city, Kamo county, Gifu prefecture
• Volcanic rocks
• Caldera
• Late Cretaceous - Paleogene (76.5, 76.3 Ma, FT)

• Sedimentary facies (Breccia): Caldera-collapse breccia
• Sedimentary facies (Breccia): Talus deposit
• Lithofacies: Rhyolite welded tuff
• Lithofacies (Minor): Tuffaceous clastic rocks, Breccia

• Thickness: 150 - 500 m or thicker
• Upper limit: Unconformity (Akaishi Welded Tuff, Yumoriyama-Kanayama Welded Tuff), Abut unconformity (Higashimata-Funayama Welded Tuff, Atera Formation, Takadaru Welded Tuff)
• Lower limit: Conformity? (Kumuro Welded Tuff), Unconformity (Mino Belt)

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

• Distribution: Ako - Shirayama - Shimosami - Furuta, Shirakawa city, Kamo county, Gifu pref.; Mount Takaderayama - Lake Tosenkyo-Kanayamako, Kanayama town, Gero city, Gifu pref.

• Wakita and Koido (1994) Geology of the Gero District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 79p. (in Japanese with English abstract 5p.)
• Mizutani and Koido (1992) Geology of the Kanayama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 111p. (in Japanese with English abstract 9p.)
• Yamada and Kobayashi (1988) Geology of the Ontakesan District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 136p. (in Japanese with English abstract 9p.)
• Kawada et al. (1988) Geology of the Hagiwara District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 82p. (in Japanese with English abstract 10p.)
• Kawada (1982) Geology of the Mikkamachi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 72p. (in Japanese with English abstract 6p.)