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Hiraki Formation (Goto and Nakada, 1956) Goto, 1986

• Type locality: Hiraki, Issai town, Tatsuno city, Hyogo prefecture
• Paleozoic volcanic island arc in the ocean (Yakuno paleo-island arc)
• Coherent formation
• Limestone: Middle Triassic, early Anisian (Foraminifera)
• Correlation: Waruishi Formation

• Sedimentary facies (Limestone): Continental shelf
• Depth of water (Limestone): Shallow marine
• Lithofacies: Mudstone, Sandstone
• Lithofacies (Upper, Minor): Conglomerate
• Lithofacies (Minor): Limestone (Ooid grainstone, Packstone)

• Thickness: 700 m or thicker
• Upper limit: Thrust fault (Yakuno Ophiolite)
• Lower limit: Thrust fault (Tatsuno Formation)

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

• Distribution: Hiraki, Issai town, Tatsuno city, Hyogo pref.; Tatsuno city - northern Aioi city, Hyogo pref.
• Fossils (Limestone): Crinoids, Bivalves, Gastropods, Brachiopods?, Calcareous algae (Garwoodia?, sp.), Bryozoans (Tabuliporella? sp., Batostomella? sp.)
• Fossils (Limestone, Foraminifera): Meandrospira dinarica, Meandrospira pusilla, Diplotremina sp., Duostomina sp., Duotaxis sp., Endoteba sp., Gandinella cf. falsofriedli, Protonodosaria? sp.

• Kobayashi (2008) Jour. Geol. Soc. Japan, vol.114, no.2, pp.80-87 DOI