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Hiketa Formation (Yehara, 1936) Yamasaki, 1986

Invalid synonym: Hiketa Shale, Ikenouchi Shale

• Type locality: Hiketa, Higashikagawa city, Kagawa prefecture
• Coherent formation
• Izumi sedimentary basin
• Forearc basin associated with strike-slip fault related to Median Tectonic Line
• Late Cretaceous, Campanian (Ammonoids, Paleomagnetism)
• Interfingered: Tanono Sandstone Member, Ebisukui Mudstone Member, Unpenji Sandstone Member, Ashiro Mudstone Member
• Correlation: Hiketa Alternation, Nakato Shale, Kaino Formation

• Sedimentary facies: Northern margin of the sedimentary basin
• Sedimentary facies: non-Turbidite
• Sedimentary facies: Submarine channel-fill deposit
• Depth of water: Outer shelf
• Lithofacies: Mudstone, Interbedded sandstone and mudstone
• Lithofacies (Minor): Sandstone, Felsic tuff
• Sedimentary structures: Slump structures

• Thickness: 300 - 2,000 m
• Upper limit: Transitional (Unpenji Sandstone Member), Conformity (Takikubo Formation, Nagoro Sandstone Member), Unconformity (Saita Formation, Koda Formation)
• Lower limit: Conformity or Interfingered (Shiroyama Formation), Unconformity (Kanonji Granite)

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

• Distribution: Dokigawa river - Kiraigawa river - Kunikinogawa river, Manno city, Nakatado county, Kagawa pref.; Hiketa, Higashikagawa city, Kagawa pref.; Maruyama - Mount Bodaiyama, Kanonji city, Kagawa pref.; Kochi - Lake Sakaseike - Yakushitoge pass, Mitoyo city, Kagawa pref.; Saitanaka - Togawa dam, Mitoyo city, Kagawa pref.
• Fossils: Fish (Teeth)
• Fossils (Ammonoids): Baculites sp., Metaplacenticeras subtiliastum
• Fossils (Bivalves): Acila yoshidai,�@Inoceramus balticus, Inoceramus aff. hetonaianus, Leionucula sp., Nanonavis elongatus amakusensis, Nostceras sp., Periplomya sp., Portlandia izumensis, Thyasira sp.
• Fossils (Radiolarians): Alievium gallowayi, Amphipternis stocki, Amphipyndax pseudoconulus, Amphipyndax tylotus, Archaeodictyomitra sp., Archaeospongoprunum hueyi, Dictyomitra koslovae, Dictyomitra multicostata, Lithomelissa heros, Stichomitra asymbatos

• Noda et al. (2021) Geology of the Ikeda District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 150p. (in Japanese with English abstract 5p.)
• Noda et al. (2017) Geology of the Kan-onji District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 96p. (in Japanese with English abstract 4p.)
• Yoshikawa et al. (2011) Jour. Geol. Soc. Japan, vol.117, no.9, pp.523-537 DOI