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Shitoka Formation (Uonuma Hills Collaborative Research Group, 1983)

• Type locality: Shitoka, Minamiuonuma city, Niigata prefecture
• Coherent formation
• late Pliocene (Calcareous nannofossils)

• Sedimentary facies: Marine
• Depth of water: Lower sublittoral zone (Shellfish fossils)
• Lithofacies: Siltstone
• Lithofacies (Minor): Interbedded sandstone and siltstone, Sandy siltstone
• Lithofacies (Lower): Gravelly mudstone

• Thickness (Kamakurazawa river): 106 m
• Thickness (Ichinosawa river): 224 m
• Upper limit: Conformity (Uonuma Formation)
• Lower limit: Unconformity (Nishitajiri Formation)

• Distribution: Kamakurazawa river - Ichinosawa river, Minamiuonuma city, Niigata pref.
• Fossils (Crustaceans): Scylla sp.
• Fossils (Calcareous nannofossils): Reticulofenestra spp., Dictyococcites spp., Coccolithus pelagicus
• Fossils (Shellfishes): Acila (Acila) divaricata, Acila (truncacila) insignis, Ennucula cyrenoides, Nuculana (Nuculana) cf. pernula, Nuculana (Thestyleda) yokoyamai, Saccella aff. sematensis, Yoldia (Cnesterium) notabilis, Portlandia (Portlandia) toyamaensis, Portlandia (Megayoldia) thraciaeformis, Nuculanidae gen. et sp. indet, Arca boucardi, Anadara (Anadara) amicula, Striarca symmetrica, Porterius dalli, Glycymeris (Glycymeris) fulgurata, Limopsis obiliqua, Modiolus difficilis, Megacrenella columbiana, Crassostrea sp., Chlamys (Chlamys) cosibensis, Swiftopecten swiftii, Yabepecten tokunagai, Anomia chinensis, Monia macroschisma, Chama sp., Lucinoma acutilineotum, Lucinidae gen. et sp. indet, Conchocele bisecta, Cycladicama cumingii, Felaniella usta, Cardita leana, Megacardita ferruginosa, Cyclocardia ferruginea, Astarte hakodatensis, Tridonta borealis, Serripes sp., Macoma (Macoma) calcarea, Pseudamiantis sp., Veneridae gen. et sp. indet, Anisocorbula venusta, Pandora wardiana, Lottia sp., Acmaea pallida, Haliotis sp., Puncturella nobilis, Homalopoma amussitatum, Pomaulax? sp., Turbinidae gen. et sp. indet, Chlorostoma sp., Cantharidus sp., Umbonium sp., Trochidae gen. et sp. indet, Cocculina sp., Bilttium sp., Clathrofenella? sp., Turritella (Neohaustator) saishuensis motidukii, Sabia sp., Trichotropis unicarinata, Cypraea sp., Cryptonatica janthostoma, Ranella yasumurai, Cymatiidae gen. et sp. indet, Ocinebrinae gen. et sp. indet, Thais cf. clavigera, Mohnia yanamii, Neptunea eos, Hindsia? sp., Siphonalia modificata, Cantharus cecillei, Lirabuccinum sp., Buccinum? sp., Oliva? sp., Mitra cf. chinensis, Pusia? sp., Neadmete sp., Paradrillia patruelis, Ophiodermella ogurana, Oenopota? sp., Propebela sp., Syrnola sp., Punctacteon kajiyamai, Siphonaria acmaeoides
• Tephra: Ichinosawa Pumiceous Tephra (Itp = Nishiyama Migakisuna Tephra, Nym, 3.35 Ma), Nishi Glassy Tephra (Nig), Shitoka Glassy Tephra (Skc), Shibakura Pumiceous Tephra (Sbp9)

• Amano et al., (2009) Jour. Geol. Soc. Japan, vol.115, no.11, pp.597-609 DOI