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Osawaguchi Tuff Member

Invalid synonym: Kokaino? Formation

• Type locality: Osawaguchi, Korofuji, Daigo city, Kuji county, Ibaraki prefecture
• Coherent formation
• Higashidaigo basin, Nishidaigo basin
• Miocene (16.7 Ma, FT, 17.3 Ma, K-Ar)

• Sedimentary facies: Terrestrial, Fluvial
• Sedimentary facies: Island arc type tholeiite, Calc-alkaline
• Sedimentary facies: Terrestrial pyroclastic flow deposit
• Sedimentary facies (Minor): Debris flow deposit, Hyperconcentrated flood flow, River deposit
• Lithofacies: I-type, Dacitic
• Lithofacies (Main): Pumice tuff, Tuffaceous sandstone
• Lithofacies (Minor): Volcanic breccia
• Sedimentary structures (Main): Cross-stratification
• Sedimentary structures (Lower): Reversed graded stratification

• Thickness (east Daigo): 130 - 150 m
• Thickness (west Daigo): 40 - 400 m
• Upper limit: Conformity (Asakawa Formation, Shidadaira Formation)

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

• Distribution: Daigo city, Kuji county, Ibaraki pref.; Shiraya pass, Hitachiomiya city, Ibaraki pref.; Yamatsuri city, Higashishirakawa county, Fukushima pref.

• Hosoi et al. (2017) Jour. Geol. Soc. Japan, vol.123, no.8, pp.613-626 DOI
• Amano et al. (2011) Jour. Geol. Soc. Japan, vol.117, Supplement, pp.69-87 DOI
• Tagiri et al. (2008) Jour. Geol. Soc. Japan, vol.114, no.6, pp.300-313 DOI