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

• Coherent formation
• Early Jurassic, Pliensbachian - Toarcian (Ammonoids)

• Sedimentary facies: Marine
• Sedimentary facies: Bottom of sedimentary basin in a inner bay
• Depth of water: Outer shelf (deeper than storm wave base)
• Lithofacies: Siltstone, Silty clay rocks
• Lithofacies (Minor): Sandy mudstone, Sandstone
• Sedimentary structures (Top): Parallel stratification

• Thickness: 550 - 580 m
• Upper limit: Conformity (Utano Formation)
• Upper limit: bottom surface of tuffaceous rock or conglomerate at the bottom of upper Utano Formation.
• Lower limit: Conformity (Higashinagano Formation)

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

• Distribution: Oka, Ochi, Shimonoseki city, Yamaguchi pref.; Ipponmatsu - Okuyama - Tabe - Tabe pass, Kikukawa village, Shimonoseki city, Yamaguchi pref.
• Fossils: Turtles, Crocodiles, Fishes, order Blattodea, Bivalves (Pseudomytiloides), Plants
• Fossils (Ammonoids): Dactylioceras sp., Cleviceras sp., Harpoceras sp.
• 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