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Yoka Formation

Invalid synonym: Tsubakiiro Volcanic Rocks

• Volcanic rocks
• Miocene (21 - 18 Ma, K-Ar; 22.1, 19.4 Ma, FT; 21.5, 21.4 Ma, U-Pb)
• Correlation: Yazu Formation, Tottori Group

• Sedimentary facies: Terrestrial
• Lithofacies: Tholeiite (Island arc - Continental-margin arc)
• Lithofacies: Basalt, Andesite
• Lithofacies: Lava, Andesitic tuff breccia
• Lithofacies (Minor): Basaltic clastic rocks, Felsic clastic rocks
• Lithofacies (Bottom): Interbedded tuffaceous sandstone, siltstone and conglomerate
• Sedimentary structures (Bottom): Trough cross-stratification

• Thickness: ca. 500 m
• Upper limit: Disconformity (Toyooka Formation)
• Lower limit: Conformity (Takayanagi Formation), Unconformity (Miyazu Granite)

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

• Distribution: southwest - northeast Tottori pref.
• Distribution: Yoka, Yabu city, Hyogo pref.; Hamasaka, Shinonsen city, Mikata county, Hyogo pref.; Muraoka, Kami city, Mikata county, Hyogo pref.; Kumihama - Amino, Kyotango city, Kyoto pref.

• Haji and Yamaji (2019) Jour. Geol. Soc. Japan, vol.125, no.9, pp.685-698 DOI
• Sakiyama et al. (2012) Jour. Geol. Soc. Japan, vol.118, Supplement, pp.1-20 DOI
• Utada (2008) Jour. Geol. Soc. Japan, vol.114, no.5, pp.231-245 DOI