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Nishizaki Formation (Naruse et al., 1951) Kawakami and Shishikura, 2006
Invalid synonym: Ageshima Formation, Ishido Group
- Type locality: Nishikawana - Sunosaki, Tateyama city, Chiba prefecture
- Coherent formation
- Trench fill sediments (Shallow accretionary compelx)
- Miocene - Pliocene (9.9 - 4.18 Ma, Radiolarians including 9.8 Ma - 5.2 Ma)
- Contemporaneous heterotopic facies: lower Hedate Formation
- Correlation: Misaki Formation, middle - upper Iwaibukuro Formation, Ishido Formation, Haraoka Formation, Kohama Formation, Koura Formation, Amatsu Formation, Kiyosumi Formation
- Sedimentary facies: Marine
- Sedimentary facies: Fore-arc basin at the ocean side from the volcanic front, or Inner trench slope
- Depth of water: Hemipelagic, Abyssal (Foraminifera)
- Lithofacies: Interbedded sandstone and tuffaceous mudstone
- Lithofacies (Minor): Tuff, Conglomerate
- Sedimentary structures: Parallel stratification, Reversed graded bedding, Slump structures, Bioturbation
- Distribution: Shirako - Fukuzawa - Anbaya, Minamiboso city, Chiba pref.; Kitaasai - Minamiasai, Chikura town, Minamiboso city, Chiba pref.; Nishikawana - Sunosaki - Kenbutsu - Fukuzawa - Konuma seashore, Tateyama city, Chiba pref.
- Fossils: Calcareous nannofossils, Trace fossils
- Fossils (Foraminifera): Globigerina nepenthes, Sphaeroidinella dehiscens
- Fossils (Radiolarians): Cyrtocapsella japonica
- Tephra: HG
- Utagawa et al. (2017) Jour. Geol. Soc. Japan, vol.123, no.11, pp.969-976 DOI
- Yamamoto et al. (2016) Jour. Geol. Soc. Japan, vol.123, no.1, pp.41-55, DOI
- Takahashi et al. (2016) Jour. Geol. Soc. Japan, vol.122, no.8, pp.375-395, DOI
- Michiguchi (2008) Jour. Geol. Soc. Japan, vol.114, no.9, pp.461-473 DOI
- Kawakami and Shishikura (2006) Geology of the Tateyama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 82p. (in Japanese with English abstract 5p.)