[ Top ] [ Japanese ]

Kokumoto Formation (Ueda, 1930) Minashi et al., 1959

Invalid synonym: Awakura Formation

• Type locality: Kokumoto, Ichihara city, Chiba prefecture
• Coherent formation
• Fore-arc basin sediments (Kazusa trough)
• Pleistocene (MIS 21 - 18)
• Correlation: Bushi Formation, Koshiba Formation, Kamo Formation, Higashinagata Formation
• Correlation (Upper): Nakazato Formation

• Sedimentary facies: Marine
• Sedimentary facies: Continental slope, Continental margin
• Sedimentary facies: Submarine canyon at the upper submarine fan
• Sedimentary facies (Sandstone): Sediment gravity flow
• Water temperature: Warm ocean current (Foraminifera)
• Depth of water: Continental shelf (Foraminifera)
• Lithofacies (Upper): Sandstone-dominant interbedded sandstone and mudstone
• Lithofacies (Upper, Minor): Siltstone, Mudstone-dominant interbedded sandstone and mudstone
• Lithofacies (Middle): Sandy mudstone
• Lithofacies (Middle, Minor): Siltstone
• Lithofacies (Lower): Sandstone-dominant interbedded sandstone and mudstone
• Lithofacies (Bottom): Sandy mudstone
• Sedimentary structures: Slump structures, Convolute lamination

• Thickness: 48 -350 m
• Thickness (Upper): ca. 80 - 90 m
• Thickness (Middle): ca. 20 - 95 m
• Thickness (Lower): ca. 115 m
• Thickness (Bottom): ca. 57 m
• Upper limit: Top of the thick sandstone bed
• Upper limit: Conformity (Kakinokidai Formation), Conformity, partly unconformity (Ichijiku Formation), Unconformity (Nagahama Sand and Gravel Member)
• Lower limit: Bottom of Ku6E
• Lower limit: Conformity (Umegase Formation)

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

• Distribution: Kokumoto, Ichihara city, Chiba pref.; Shibahara - Myorakuji, Mutsuzawa city, Chosei county, Chiba pref.; Sarubukuro, Mobara city, Chiba pref.; Nishiawakura - Kujukutani, Kimitsu city, Chiba pref.; Morokuzure, Futtsu city, Chiba pref.; Ichinono, Chonan city, Chosei county, Chiba pref.
• Fossils: Mammuthus sp., Rorqual whales
• Fossils (Shellfishes): Acila divaricata, Admete cancellata, Admete couthouyi, Admete watanabei, Aforia circinata, Aforia diomedea, Ancistrolepis trochoidens, Bathybembix crumpi, Boreoscala densicostata, Boreotrophon alaskanus, Cavolinia sp., Clio sp., Diacria sp., Euspila pallida, Euspila plicispira, Fulgoraria sp., Fusitriton oregonsis, Inquisitor sp., Limopsis tokaiensis, Limopsis uwadokoi, Macoma calcarea, Mitrella? sp., Natuoides spp., Nematoma microvoluta, Nuculana ikebei, Obestoma? sp., Plicifusus bella, Portlandia (Portlandella) lischkei, Propebela caondida, Propebela venusta, Rectiplanes sonctiioannis, Riughudrilla mediocorinata, Suavodrilia engonia, Volutopsis hirasei, Yoldia lischkei
• Fossils (Foraminifera): Bolivinita quadrilatera, Bulimina aculeata, Cassidulina subglobosa, Cassidulinoides bradyi, Cibicides aknerianus, Elphidium clavatum, Elphidium crispum, Globigerinoides ruber cyclostomus, Globigerinoides trilobus, Globoquadrina dutertrei, Globorotaria inflata, Globorotalia tosaensis, Globorotalia truncatulinoides, Gyroidina arbicularis, Lagenonodosaria scalaris, Neoglogoqudrina incompta, Neoglogoqudrina inflata, Neoglogoqudrina pachyderma, Nonion nicobarense, Pseudoeponides japonicus, Pseudononion japonicum, Pulleniatina obliquiloculata
• Fossils (Diatoms): Nitzschia fossilis
• Fossils (Radiolarians): Dictyocoryne spp., Didymocyrtis spp., Lithomelissa setosa, Stylochlamydium venustum, Tetrapyle spp.
• Fossils (Calcareous nannofossils): Gephyrocapsa parallela, Pseudoemiliania lacunosa
• Fossils (Pollen): Fagus sp., Juglans mandshurica, Larix sp., Menyanthes sp., Metasequoia sp., Picea sp., Quercus sp.
• Fossils (Trace fossils): Alcyonidiopsis isp., Chondrites isp., Nereites isp., Palaeophycus isp., Phycosiphon isp., Planolites isp., Scolicia isp., Skolithos isp., Teichichnus isp., Thalassinoides isp., Trichichnus isp., Zoophycos isp.
• Tephra: Ku0.1, Ku0.2, Ku0.3, Ku0.5, Ku0.6, Ku0.7, Ku0.9, Ku1 (Hkd-Ku), Ku1.4A, Ku1.4B, Ku1.5, Ku2A, Ku2B, Ku2.3 (On-Byk), Ku2.5, Ku3, Ku3.5, Ku4, Ku4.5, Ku5A, Ku5B, Ku5C, Ku5D, Ku6A, Ku6B, Ku6C, Ku6D, Ku6D', Ku6E

• Utsunomiya and Ooi (2019) Geology of the Kazusa-Ohara District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 127p. (in Japanese with English abstract 4p.)
• Tamura et al. (2019) Jour. Geol. Soc. Japan, vol.125, no.1, pp.23-39 DOI
• GSSP proposal group (2019) Jour. Geol. Soc. Japan, vol.125, no.1, pp.5-22 DOI
• Nanayama et al. (2016) Geology of the Mobara District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 101p. (in Japanese with English abstract 4p.)
• Suzuki and Murata (2011) Jour. Geol. Soc. Japan, vol.117, no.7, pp.379-397 DOI
• Nakajima and Watanabe (2005) Geology of the Futtsu District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 102p. (in Japanese with English abstract 8p.)
• Tokuhashi and Endo (1984) Geology of the Anesaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 136p. (in Japanese with English abstract 6p.)