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Yoshiwa Group Takahashi et al., 1989
- Type locality: Nakatsuyagawa river, Hatsukaichi city, Hiroshima prefecture
- Paleozoic volcanic island arc in the ocean (Yakuno paleo-island arc)
- Coherent formation
- Deposition (Siliceous shale): middle - late Permian (Radiolrians)
- Deposition (Mudstone): middle - late Permian (Radiolrians)
- Correlation: Maizuru Group
- Correlation (Ultramafic rocks): Yakuno Complex
- Intruded by: Hiroshima Granites
- Sedimentary facies: Marine
- Lithofacies (Upper): Mudstone
- Lithofacies (Upper, Minor): Basalt hyaloclastite, Lava, Pillow lava, Siliceous shale, Sandstone
- Lithofacies (Lower): Basalt hyaloclastite, Lava
- Lithofacies (Lower, Minor): Serpentinite, Gabbro, Siliceous shale
- Sedimentary structures: Parallel stratification
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Yoshiwa - Yoshiwagawa river - Nakatsuyagawa river - Shioyagawa river - Omachiya - Mount Megahirayama - Minochigawa river - Ichino - Mount Omineyama - Mominoki-shinrinkoen park, Hatsukaichi city, Hiroshima pref.; Yuki town - Shii - Otada - Shirai - Mamedochi - Mount Mukaiyama - Mount Mamedochi - Kurotani - Awabashira, Hiroshima city, Hiroshima pref.; Shisogawa river, Hikimi town, Masuda city, Shimane pref.
- Fossils: Sponges (Spicules)
- Fossils (Radiolarians): Follicucullus scholasticus, Pseudoalbaillella sp.
- Kimura et al. (2019) Jour. Geol. Soc. Japan, vol.125, no.2, pp.153-165 DOI
- Takahashi (1991) Geology of the Hiroshima District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 41p. (in Japanese with English abstract 3p.)
- Takahashi et al. (1989) Geology of the Tsuda District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 56p. (in Japanese with English abstract 4p.)