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Ayukawa Formation Watanabe, 1920

Invalid synonum: Ayukawa Slate Formation

• Type locality: Ayukawa, Hitachi city, Ibaraki prefecture
• Continental shelf sediments
• Deposition: early Permian (Fusulinids)
• Metamorphism: Early - Late Cretaceous (118.0 - 96.0, K-Ar)

• Lithofacies (Protolith): Slate rich in volcaniclastic rocks, Sandstone
• Lithofacies (Protolith, Minor): Limestone

• Upper limit: Unknown
• Lower limit: The position where slate becomes dominant (Daioin Formation)

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

• Distribution: Ayukawa, Hitachi city, Ibaraki pref.
• Fossils (Ishinazaka fauna): Brachiopods
• Fossils: Fusulinids, Bryozoans, Crinoids
• Fossils (Gravel in Kume Formation, Brachiopods): Isogramma heritschi, Kitakamichonetes multicapillatus, Transennatia gratiosa, Spinomarginifera kueichowensis, Bathymyonia ussurica, Bathymyonia neimongolica, Urushtenoidea chaoi, Linoproductus sp., Permianella typica, Dicystoconcha lapparenti, Schuchertella debaisiensis, Uncinunellina timorensis, Cleiothyridina sp., Martinia sp., Spiriferella sp., Spiriterellina fredericksi, Whitspakia sp., Leptodus nobilis

• Tazawa et al. (2018) Jour. Geol. Soc. Japan, vol.124, no.11, pp.913-918 DOI
• Tagiri et al. (2016) Jour. Geol. Soc. Japan, vol.122, no.6, pp.231-247, DOI
• Tagiri et al. (2011) Jour. Geol. Soc. Japan, vol.117, Supplement, pp.1-20 DOI