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Akka Unit (Sugimoto, 1974)

Invalid synonym: Sawayamagawa Formation, Akka Formation, Akka Limestone

• Type locality (Old): Akka, Iwaizumi city, Shimohei county, Iwate prefecture
• Type locality (New): Taki, Yamane town, Kuji city, Iwate prefecture
• Accretionary complex
• Deposition (Limestone): Late Triassic, Carnian - Norian (Conodont)
• Accretion: Jurassic or later

• Sedimentary facies: Marine
• Sedimentary facies (Lower): Oceanic island basalt
• Lithofacies (Upper): Muddy limestone, Limestone (Akka Limestone)
• Lithofacies (Upper, Minor): Calcareous mudstone, Chert
• Lithofacies (Lower): Basalt lava, Pillow lava, Basaltic pyroclastic rocks
• Lithofacies (Lower, Minor): Tuffaceous mudstone, Interbedded basaltic tuff breccia and limestone

• Thickness: 100 - 800 m
• Upper limit: Kawai - Oguni - Kuriyama Fault

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

• Distribution: Akka, Iwaizumi city, Shimohei county, Iwate pref.; Mawatari - Uchimagi - Kiurinai, Yamane town, Kuji city, Iwate pref.; Tobetsu river, Shimohata - Derumachi, Kawai, Yamagata town, Kuji city, Iwate pref.
• Fossils (Limestone, Magidai Formation?): Hexacorals, Calcareous algae (Thecosmilia? sp., Solenopora sp.), Sponges
• Fossils (Conodonts): Epigondolella abneptis

• Takahashi et al. (2016) Jour. Geol. Soc. Japan, vol.122, no.1, pp.1-22, DOI
• Ehiro et al. (2008) Jour. Geol. Soc. Japan, vol.114, Supplement, pp.121-139 DOI
• Yoshida et al. (1987) Geology of the Rikuchu-Ono District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 70p. (in Japanese with English abstract 6p.)