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Toyono Formation (Suzuki, 1938) Tomizawa, 1954
Invalid synonym: Samizu Formation, Akashio Formation
- Type locality: Toyono hills, Toyono, Nagano city, Nagano prefecture
- Coherent formation
- The first lacustrine deposit in Nagano basin
- middle Pleistocene
- Sedimentary facies: Lacustrine
- Lithofacies (Upper): Sands, Gravels
- Lithofacies: Sands, Sandy silt
- Lithofacies (Minor): Silt
- Sedimentary structures (Silt): Parallel stratificaiton
- Sedimentary structures (Gravels): Cross stratification
- Sedimentary structures: The partial unconformity between the upper and the lower part is names as Koshibami Unconformity.
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Tago river - Dokyo river - Asakawa-Nishijo - Tanaka - Shiroyama - Ojoji, Nagano city, Nagano pref.; Shirasaka pass - Toyono hills, Toyono, Nagano city, Nagano pref.; Gongen creek - Horiki creek - Kyokadai - Nishigawara, Amori, Nagano city, Nagano pref.
- Fossils (Toyono non-marine fauna): Anodonta (Sinanodonta) lauta, Cipangopaludina chinensis, Cipangopaludina japonica, Corbicula atrata, Corbicula leana, Cristaria cf. plicata, Inversidens japanensis, Semisulcospira (Semisulcospira) reiniana
- Fossils (Diatoms): Amphora veneta, Melosira islandica subsp. helvefica, Navicula placentula forma rostrata, Synedra ulna
- Sugito et al. (2015) Jour. Geol. Soc. Japan, vol.121, no.7, pp.217-232, DOI
- 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.)
- Akahane et al. (1992) Geology of the Nakano District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 106p. (in Japanese with English abstract 4p.)
- 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.)