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Hosoura Formation (Mabuti, 1932) Onuki, 1956
Invalid synonym: Gongen Formation
- Type locality: Hosoura seashore, Shizukawa, Minamisanriku city, Motoyoshi county, Miyagi prefecture
- Coherent formation
- Early Jurassic, Sinemurian - Middle Jurassic, Aalenian
- Sedimentary facies: Marine
- Sedimentary facies: Slope - bottom of sedimentary basin
- Lithofacies (Upper): Sandy mudstone
- Lithofacies (Upper, Minor): Sandstone
- Lithofacies (Lower): Interbedded sandstone and mudstone
- Sedimentary structures: Less trace fossils than Hashiura Group
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Hosoura - Gongen - Nakazai, Shizukawa, Minamisanriku city, Motoyoshi county, Miyagi pref.; Aikawa creek, Kitakami town, Ishinomaki city, Miyagi pref.; Maezawa creek - Moza creek - Takihama creek, Zaigo, Minamisanriku city, Motoyoshi county, Miyagi pref.
- Fossils: Leptopterygius aff. burgundiae, Bivalves (Pecten? sp., Vaugonia kodaijimensis)
- Fossils (Ammonoids): Arnioceras yokoyamai, Graphoceras sp., Hammatoceras kitakamiense, Hammatoceras tuberculatum, Harpoceras okadai, Hosoureites ikianus, Hosoureites satoi, Leioceras sp., Lytoceras sp., Planammatoceras chibai, Planammatoceras subitle, Schlotheimia aff. amblygonia, Schlotheimia schimizui, Timetoceras recticostatum
- Ehiro and Morikiyo (2013) Jour. Geol. Soc. Japan, vol.119, Supplement, pp.47-67 DOI
- Takeuchi and Kaneko (1996) Geology of the Shizugawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 93p. (in Japanese with English abstract 5p.)
- Kamada (1993) Geology of the Tsuya District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 70p. (in Japanese with English abstract 6p.)
- Takizawa et al. (1990) Geology of the Toyoma District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 126p. (in Japanese with English abstract 8p.)