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Bessho Formation Honma, 1927

Invalid synonym: Akashina Formation

• Type locality: Yukawa river, Besshoonsen, Ueda city, Nagano prefecture
• Coherent formation
• middle Miocene (Foraminifera)
• Intruded by: Quartz diorite, Quartz porphyry, Hornblende porphyry, Diorite porphyry
• Correlation: Iseyama Formation, lower Asakawa Formation, Takai Shale Member

• Sedimentary facies: Deep marine
• Sedimentary facies: Reductive
• Lithofacies: Shale
• Lithofacies (Basal): Glauconite sandstone, Tuffaceous sandstone
• Lithofacies (Minor): Sandstone, Sandy mudstone, Tuffaceous mudstone, Gravelly sandstone, Interbedded sandstone and shale, Tuff, Andesite tuff, Lava
• Sedimentary structures (Top): Clastic dykes
• Sedimentary structures: Slump structures

• Thickness: 100 - 2,000 m
• Upper limit: Conformity (Aoki Formation, Hitoeyama Member), Unconformity (Older Josho Lake Deposit, Makiuchi Andesite, Kiyotaki Volcanics)
• Lower limit (Mori Member): Top of t3 Dacite Tuff
• Lower limit: Conformity (Uchimura Formation, Kariyahara Sandstone and Mudstone Member, Toyosaka Member, Fujiyama Formation)

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

• Distribution: Yukawa river, Besshoonsen, Ueda city, Nagano pref.; Fujiyama - Koaso - Maeyama - Mount Megamidake, Ueda city, Nagano pref.; Shogunzuka, Mori, Chikuma city, Nagano pref.; Isobe, Chikuma city, Nagano pref.; Toyosaka - Hikagezawa - Inaba - Mitaki, Matsushiro town, Nagano city, Nagano pref.; Mount Garyuzan, Suzaka city, Nagano pref.; Koami, Sakaki city, Hanishina county, Nagano pref.; Tazawa hot spring - Kutsukake hot spring, Aoki city, Chiisagawa county, Nagano pref.; Yokokawa - Yakyu, Shiga, Matsumoto city, Nagano pref.; Nagamine, Akashina, Azumino city, Nagano pref.
• Fossils: Whales, Dolphins, Fish scales (Sardinops sp.), Echinoids (Schizaster sp.), Sponges (Sagarites chitanii), Flowering plants (Salix sp.), Foraminifera
• Fossils (Shellfishes): Adulomya uchimuraensis, Anadara watanabei, Anisocorbula venusta, Barbatia sp., Bittium? sp., Buccinum koyamai, Cadela sp., Calyptraea cf. aokii, Calyptraea kobayashii, Calyptraea tokunagai, Calyptraea tubula, Cardium? sp., Chlamys sp., Chlorostoma shinanoensis, Conchocele nipponica, Crenella sp., Cylichna cf. kozukensis, Dentalium (Fissidentalium) yokoyamai, Diodora cf. yokoyamai koshibensis, Fulgolaria sp., Glycymeris sp., Laevicardium angustum, Lima? sp., Liocyma cf. terrera, Lucinoma acutilineata, Lucinoma otukai, Margarites sp., Modiolus akanudaensis, Monia cf. macrochisma, Mya cf. japonica, Neverita didyma, Neverita fissuratus, Palliolum (Delectopecten) peckhami, Paphia sp., Pateloida sp., Patinopecten sp., Portlandia (Portlandia) yotsukurensis, Pyramidella? sp., Saccella confusa, Saccella confusa kongiensis, Semele sp., Tectonatica janthostomoides, Tellina sp., Turbo? sp., Turcica coreensis, Umbonium sp., Venericardia sp.
• Fossils (Brachiopods): Coptothyris grayi, Terebratalia gouldi
• Fossils (Foraminifera): Cyclammina cancellata, Cyclammina incisa, Cyclammina japonica, Cyclammina orbicularis, Cyclammina pacifica, Cyclammina pucilla, Haplophragmoides renzi
• Deposit: Inkstone (so called Murasameishi)

• Harayama et al. (2009) Geology of the Matsumoto District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 63p. (in Japanese with English abstract 3p.)
• Nagamori et al. (2003) Geology of the Togakushi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 109p. (in Japanese with English abstract 3p.)
• Kato and Akahane (1986) Geology of the Nagano District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 120p. (in Japanese with English abstract 5p.)
• Kato and Sato (1983) Geology of the Shinano-Ikeda District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 93p. (in Japanese with English abstract 7p.)
• Kato (1980) Geology of the Sakaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 57p. (in Japanese with English abstract 5p.)
• Ota and Katada (1955) Suzaka, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 54p. (in Japanese with English abstract 6p.)