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Hosokura Formation Hosokura Mine ex Hattori and Takahashi, 1953

Invalid synonym: Yutorinuma Formation, Matago Formation, Kanizawa Formation, Nakayama Propylite

• Type locality: Hosokura mine, Uguisuzawa, Kurihara city, Miyagi prefecture
• Coherent formation
• middle Miocene

• Sedimentary facies (Upper): Shallow marine
• Sedimentary facies (Upper): Lower continental shelf (Foraminifera)
• Sedimentary facies (Upper, Rhyolite): Lava dome
• Water temperature (Upper): Warm ocean current (Foraminifera)
• Lithofacies (Andesite): Low alkali tholeiite series, Calc-alkaline
• Lithofacies (Upper): Acidic tuff, Tuffaceous sandstone, Mudstone, Rhyolite - Dacite lava, Pyroclastic rocks
• Lithofacies (Lower): Andesite lava, Pyroclastic rocks (Hyaloclastite), Rhyolite lava, Tuff, Tuff breccia, Pumice tuff, Tuffaceous sandstone
• Lithofacies (Lower, Minor): Siltstone

• Thickness: 550 m or thicker
• Upper limit: Unconformity (Kuzumine Formation, Hanayamazawa Formation, Onomatsuzawa Formation, Odogamori Formation, Onoda Formation)
• Lower limit: Unconformity (Granitoids)

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

• Distribution: Hosokura mine - Mount Odogamori, Uguisuzawa, Kurihara city, Miyagi pref.; Toishizawa - Azabu, Hanayama, Kurihara city, Miyagi pref.; Kunimi pass, Sendai city, Miyagi pref.; Kawaguchi - Odomori, Ichihasama, Kurihara city, Miyagi pref.; Kokurosaki - Kawatabi - Kayobara, Narukoonsen, Osaki city, Miyagi pref.
• Fossils: Echinoids (Linthia nipponica), Brachiopods (Terebratulina sp.), Sponges (Aphrocallistes sp.)
• Fossils (Shellfishes): Chlamys cf. kaneharai, Chlamys cf. miyatokoensis, Cyclocardia siogamensis, Gloripallium crassivenium, Kotorapecten kagamianus, Mercenaria yokoyamai, Mizuhopecten sp., Modiolus yasuhiroi, Nanaochlamys notoensis, Neptunea? sp., Palliolum sp., Pitar? sp., Vasticardium sp., Venus treuma
• Fossils (Foraminifera): Amphicoryna scalaris sagamiensis, Cassidulina laevigata carinata, Elphidium sendaiense, Florilus japonicus, Globigerina praebulloides, Globigerina woodi, Globigerinita glutinata, Globigerinoides trilobus, Globocassidulina subglobosa, Globorotalia bella, Guttulina orientalis, Hanzawaia nipponica, Lenticulina lucida, Lenticulina miyagiensis, Lenticulina nikobarensis, Lenticulina orbicularis, Lenticulina pseudorotulata, Melonis pompilioides, Oolina melo, Sigmoidella pcifica, Sigmomorphina notoensis

• Tsuchiya et al. (1997) Geology of the Iwagasaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 96p. (in Japanese with English abstract 4p.)