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Utano Formation (Kobayashi, 1926), Yamada and Ohno, 2005

• Coherent formation
• Early Jurassic, Toarcian - Middle Jurassic, Bajocian (Ammonoids)

• Sedimentary facies: Marine
• Sedimentary facies: Prodelta slope in a inner bay
• Sedimentary facies: Turbidite
• Sedimentary facies (Bottom): Debris flow
• Depth of water: Outer shelf (deeper than storm wave base)
• Lithofacies: Mudstone, Mudstone-dominant interbedded sandstone and mudstone, Siltstone, Sandy mudstone
• Lithofacies (Minor): Sandstone
• Lithofacies (Bottom): Tuffaceous sandstone, Conglomerate
• Sedimentary structures: Parallel stratification, Cross stratification, Convolute lamination

• Thickness: 150 - 1,100 m or thicker
• Upper limit: Unconformity (Kanmon Group, Toyonishi Group)
• Lower limit: Conformity (Nishinakayama Formation)
• Lower limit: bottom of tuffaceous rock or conglomerate

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

• Distribution: Nakao, Ochi, Shimonoseki city, Yamaguchi pref.; Tabe - Ono, Shimonoseki city, Yamaguchi pref.; west of Mount Ongasa, Shimonoseki city, Yamaguchi pref.; Nanami - Yoshika, Kikukawa village, Shimonoseki city, Yamaguchi pref.
• Fossils (Ammonoids): Holcophylloceras sp., Pseudolioceras sp., Phymatoceras sp.
• Fossils (Bivalves): Retroceramus utanoensis, Planammatoceras sp., Hildoceratidae gen. et sp. indet, Inoceramus utanoensis
• Fossils (Trace fossils): Phycosiphon isp.

• Maeda and Oyama (2019) Jour. Geol. Soc. Japan, vol.125, no.8, pp.585-594 DOI
• Kawamura (2010) Jour. Geol. Soc. Japan, vol.116, no.1, pp.27-44 DOI