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Torisakagawa Formation (Haga, 2001) Kano et al., 2012

Invalid synonym: lower Aniai Formation, Hitachinai Basalt Member, Aniai Coal-bearing Member

• Type locality: Nekko - Shirasaki creek - Sugisawa creek - Iwanome creek - Torisaka river - Ani river, Koyawatari, Ani, Kitaakita city, Akita prefecture
• Volcanic rocks
• early Miocene (22 Ma, 25 - 19 Ma, K-Ar)

• Sedimentary facies: Terrestrial
• Sedimentary facies (A part): Pyroclastic surge deposit
• Sedimentary facies (Dacite): Pyroclastic flow deposit
• Lithofacies: Basalt - Andesite lava, Scoria volcanic lapilli tuff, Agglutinates, Lapilli stone, Volcanic lapilli tuff, Tuff, Hyaloclastite, Volcanic breccia, Pillow lava, Dacite pyroclastic rocks
• Lithofacies (Minor): Shale, Siltstone, Tuffaceous sandstone, Sandstone, Conglomerate, Acidic tuff, Coal
• Sedimentary structures: Graded bedding

• Thickness: 500 - 1,800 m
• Upper limit: Unconformity (Himegatake Andesite)
• Lower limit: Onlap unconformity (Omata Formation), Unconformity (Haginari-Okuramatasawa Formation, Taiheizan Granodiorite)

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

• Distribution: Nekko - Shirasaki creek - Sugisawa creek - Iwanome creek - Torisaka river - Ani river, Koyawatari, Ani, Kitaakita city, Akita pref.; Horiuchi creek, Koani river, Kamikoani city, Kitaakita county, Akita pref.
• Fossils (Aniai flora): Acer heigunensis, Acer macrosamarum, Acer megasamarum, Acer palaeoplatanoides, Acer protomiyabei, Acer protonegundo, Acer pseudocarpinifolium, Acer pseudoginnala, Acer rotundatum, Aesculus majus, Ailanthus ezoense, Alangium aequalifolium, Alnus arasensis, Alnus miojaponica, Alnus sakaii, Alnus tsudae, Alnus usyuensis, Betula hommae, Betula mioluminifera, Betula nathorsti, Carpinus heigunensis, Carpinus subcordata, Cercidiphyllum crenadum, Cladorastis sp., Diospyros miokaki, Fagus antipofi, Glyptostrobus europaeus, Juglans sp., Hemitrapa borealis, Maackia ugoensis, Magnolia nipponica, Metasequoia occidentalis (= Metasequoia japonica), Nelumbo endoana, Ostrya shiragiana, Picea kaneharai, Picea kanoi, Picea ugoana, Pinus cf. trifolia, Populus balsamoides, Populus latior, Pseudolarix sp., Pterocaya sp., Quercus sinomiocenicum, Ribes sp., Rhus aniensis, Salix varians, Schisandra sp., Sciadopitys shiragiana, Sorbus cf. hokiensis, Sorbus uzenensis, Taiwania sp., Tetracentron sp., Thuja iwasae, Thuja nipponica, Tilia hommashinichii, Tilia sekiensis, Ulmus shiragica, Ulmus takayasui, Wisteria fallax, Zelkova ungeri

• Kano (2018) Jour. Geol. Soc. Japan, vol.124, no.10, pp.781-803 DOI
• Kano et al. (2012) Geology of the Aniai District, 2nd Edition, 1:50,000 Quadrangle Series, Geological Survey of Japan, AIST, 59p. (in Japanese with English abstract 4p.)
• Ozawa and Sumi (1958) Tazawako, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 23p. (in Japanese with English abstract 4p.)
• Ozawa and Sumi (1957) Moriyoshiyama, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 42p. (in Japanese with English abstract 5p.)