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Kurotaki Formation Ueda, 1930

Invalid synonym: Takeoka Formation, Komaba Formation

• Type locality: Kurotaki fall, Obitsugawa river, Kimitsu city, Chiba prefecture
• Coherent formation
• Fore-arc basin sediments (Kazusa trough)
• Basal conglomerate of Kazusa Group
• Pliocene
• Contemporaneous heterotopic facies: Katsuura Formation, Namihana Formation, Ohara Formation, Kiwada Formation, Tomiya Formation
• Correlation: Nojima Formation, Sagashi Formation

• Sedimentary facies: Shallow marine
• Sedimentary facies: Transgressive stage deposit
• Sedimentary facies: Continental shelf, Continental margin, Continental slope
• Sedimentary facies: Channel-fill deposit
• Lithofacies: Tuffaceous sandstone, Tuffaceous conglomerate
• Lithofacies (Minor): Tuffaceous muddy sandstone, Tuffaceous sandy mudstone
• Sedimentary structures: Hummocky cross-stratification, Slump structure, Clastic dikes
• Paleocurrent: South to North, West to East (Cross stratification)

• Thickness: 0.7 - 150 m
• Upper limit: Transitional (Tomiya Formation)
• Lower limit: Kurotaki Unconformity (Anno Formation, Kunawa Sandstone Member)

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

• Distribution: Kurotaki fall, Obitsugawa river, Kimitsu city, Chiba pref.; Mount Mitsuishiyama, Kimitsu city, Chiba pref.; Shikoma river - Tomiya - Takeoka seashore - Hagiu - Seki, Futtsu city, Chiba pref.; Hoge, Katsuura city, Chiba pref.
• Fossils: Echinoids, Brachiopods, Calcareous algae, Foraminifera (Globigerina sp.)
• Fossils (Shellfishes): Acesta sp., Calyptogena sp., Chlamys vesiculosa, Glycymeris sp., Lima sp., Limopsis sp., Mikadotrochus sp., Patinopecten sp., Turbo sp.

• 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
• Yamamoto et al. (2016) Jour. Geol. Soc. Japan, vol.123, no.1, pp.41-55, DOI
• 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.)
• Suzuki et al. (1990) Geology of the Nago District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 48p. (in Japanese with English abstract 3p.)