[ Top ] [ Japanese ]

Osawa Formation Ichikawa, 1947

• Type locality: Osawa seashore, Motoyoshi village, Kesennuma city, Miyagi prefecture
• Coherent formation
• Early Triassic, Olenekian (Ammonoids)
• Contemporaneous heterotopic facies (Partly): Fukkoshi Formation
• Intruded by: Orikabe Plutonic Complex

• Sedimentary facies: Marine
• Sedimentary facies: Turbidite
• Sedimentary facies (Upper): Deeper than storm wave base
• Sedimentary facies (Lower): Outer continental shelf
• Sedimentary facies (Lower, Conglomerate): Channel-fill depsosit
• Lithofacies: Calcareous mudstone
• Lithofacies (Minor): Sandstone, Interbedded sandstone and mudstone
• Lithofacies (Lower): Interbedded calcareous sandstone and mudstone
• Lithofacies (Lower, Minor): Conglomerate
• Sedimentary structures: Parallel lamination, Slump structures, Decollement-type land slide, Wave ripples, Convolute stratification, Trace fossils

• Thickness: 200 - 700 m
• Upper limit: Transitional (Fukkoshi Formation)
• Lower limit: Bottom of slate facies overlying sandstone facies
• Lower limit: Transitional (Hiraiso Formation)

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

• Distribution: Osawa seashore - Magomecho - Mount Tatsugane - Goonozawa - Terayogai - Urushibara - Karyo, Motoyoshi town, Kesennuma city, Miyagi pref.; Tanoura - Cape Tatezaki - Namiita - Nagaha, Minamisanriku city, Motoyoshi county, Miyagi pref.; Mount Omori - Mount Atago, Ichinoseki city, Iwate pref.; Kamihazawa - Shimohazawa - Hineushi, Toyoma town, Tome city, Miyagi pref.; Tajiribatake - Sonae - Iriobunezawa, Minamisanriku city, Motoyoshi county, Miyagi pref.; Oyashiki - Mount Tenjin - Yanaizu, Tsuyama town, Tome city, Miyagi pref.; Mount Inumuri, Toyosato town, Tome city, Miyagi pref.; Mizuhama - Funakoshi - Cape Togezaki - Namiita - Mount Takanashi, Ogachi town, Tome city, Miyagi pref.; Ozashi - Terahama, Kitakami town, Ishinomaki city, Miyagi pref.; Sashigahama - Onmaehama - Goten pass - Ishihama - Washinokami - Harinohama - Anju, Onagawa city, Oshika county, Miyagi pref.; Kofunakoshi - Yatsu - Omori - Motofunaba - Kaneyama, Ishinomaki city, Miyagi pref.; Enoshima island, Onagawa city, Oshika county, Miyagi pref.
• Fossils: Utatsusaurus hataii, Ogatsusaurus microdentata, Sharks (Hybodus sp.), Conulariida (Conulariopsis quadrata)
• Fossils (Ammonoids): ): rnautoceltites sp., Arnautoceltotes sp., Columbites parisianus, Dalmatites sp., Danubites aff. ambika, Eophyllites cf. dieneri, Euflemingites sp., Isculitoides sp., Japonites planiplicatus, Keyserlingites cf. midendorffi, Leiophyllites aff. pitahama, Leiophyllites aff. pradyumna, Meekoceras sp., Metadagnoceras motoyoshiense, Nordophiceras sp., Ophiceras sp., Preflorianites aff. sulioticus, Prenkites cf. timorensis, Procarnites kokeni, Stacheites sp., Subcolumbites perrinismithi, Xenoceltites cf. crenoventrosus, Xenodiscus sp.
• Fossils (Bivalves): Bellerophon sp., Deltopecten? sp., Eumorphotis cf. martini, Eumorphotis cf. murtiformis, Eumorphotis aff. telleri, Leptochondria hataii, Palaeonucula? sp., Pecten amuricus, Posidonia sp.
• Fossils (Brachiopods): Lingula sp., Orbiculoidea sp.
• Fossils (Plants): Equisetites? sp., Neocalamites muratae, Pleuromeia hataii
• Fossils (Gravels): Fishes (Teeth), Trilobites, Gastropods, Crinoids (Zaphrentid corals), Sponges (Spicules), Bryozoans
• Fossils (Gravels, Conodonts): Adetognathus lautus, Hibbardella sp., Hindeodella sp., Idiognathoides noduliferus, Idiognathoides sinuatus, Idiognathoides sulcaatus, Ozarkodina sp.

• Ehiro and Morikiyo (2013) Jour. Geol. Soc. Japan, vol.119, Supplement, pp.47-67 DOI
• Takeuchi and Mikoshiba (2002) Geology of the Senmaya District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 76p. (in Japanese with English abstract 3p.)
• 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.)
• Kamada and Takizawa (1992) Geology of the Osu District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 69p. (in Japanese with English abstract 4p.)
• 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.)
• Takizawa et al. (1987) Geology of the Yoriiso District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 74p. (in Japanese with English abstract 5p.)
• Takizawa et al. (1984) Geology of the Ishinomaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 103p. (in Japanese with English abstract 7p.)
• Kambe and Shimazu (1961) Kesennuma, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 73p. (in Japanese with English abstract 16p.)