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Asakawa Formation

• Type locality: along Asa river, Daigo city, Kuji county, Ibaraki prefecture
• Type locality (redefined by Otsuki, 1975): Kawashimo - Takikura - Oenchi, Daigo city, Kuji county, Ibaraki prefecture
• Coherent formation
• Higashidaigo basin, Nishidaigo basin
• middle Miocene

• Sedimentary facies (Upper): Brackish
• Sedimentary facies (Middle): Fluvial
• Sedimentary facies (Lower): Fluvial, Lacustrine
• Sedimentary facies (Upper): Inner bay - Estuary, Tidal flat, Fan delta
• Sedimentary facies (Middle): Braided river, Fan
• Sedimentary facies (Lower, Main): Fan
• Sedimentary facies (Lower, Minor): Lake, Talus
• Climate (Main): Warm temperate
• Climate (Top): Subtropical
• Lithofacies (Upper, Main): Tuffaceous sandstone
• Lithofacies (Upper, Minor): Siltstone, Gravelly sandstone, Conglomerate, Sandstone-dominant interbedded siltstone and sandstone, Lignite
• Lithofacies (MIddle, Main): Tuffaceous sandstone
• Lithofacies (Middle, Minor): Conglomerate, Lignite, Gravelly sandstone
• Lithofacies (Lower, Main): Sandstone-dominant interbedded sandstone and siltstone
• Lithofacies (Lower, Minor): Lignite, Conglomerate
• Sedimentary structures (Upper): Trough cross-stratification, Slump structures, Wave-formed ripples
• Sedimentary structures (Middle): Trough cross-stratification

• Thickness (east Daigo): 1,010 - 1,330 m
• Thickness (west Daigo): 1,760 m or thinner
• Thickness (Upper): 640 - 980 m
• Thickness (Lower): 420 - 1,160 m
• Upper limit: Conformity (Nantaisan Volcanic Breccia)
• Lower limit: 16.7 - 16.4 Ma (Inferred)
• Lower limit: Conformity (Kitatage Formation)

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

• Distribution: Kawashimo - Takikura - Oenchi - Arayashiki - Akutsu - Onodaira - Kitazawa, Daigo city, Kuji county, Ibaraki pref.
• Fossils (Bivalves): Geloina stachi, Anadara kakehataensis, Lucinoma sp., Luisinisca sp., Cyclina japonica, Clementia sp., Felaniella sp., Dosinia sp., Ostrea gravitesta
• Fossils (Gastropods): Vicarya callosa japonica, Battillaria sp.
• Fossils (Daijima type flora): Carpinus miocenica, Castanea ungeri, Quercus mandraliscae, Zelkova ungeri, Liquidambar mioformosana, Rhus protoambigua, Liquidambar miosinica, Alnus usyuensis, Comptonia naumanni, Salix miosinica
• Fossils (Mangrove pollen): Kandelia sp., Sonneratia sp.
• Fossils (Footprints): Elephants

• Hosoi et al. (2017) Jour. Geol. Soc. Japan, vol.123, no.8, pp.613-626 DOI
• Yamanoi et al. (2011) Jour. Geol. Soc. Japan, vol.117, no.9, pp.538-543 DOI
• Amano et al. (2011) Jour. Geol. Soc. Japan, vol.117, Supplement, pp.69-87 DOI
• Tagiri et al. (2008) Jour. Geol. Soc. Japan, vol.114, no.6, pp.300-313 DOI