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Hiraki Welded Tuff Yoshida and Kawata, 1987

Invalid synonym: Saikojiyama Formation

• Type locality (Upper): Kiyomizuji temple, Hiraki, Kato city, Hyogo prefecture
• Type locality (Lower): Kuroishi dam, Konda town, Nishiwaki city, Hyogo prefecture
• Volcanic rocks
• Late Cretaceous (72.7, 70.7 Ma, K-Ar)
• Correlation (Lower): Moshi Welded Tuff, Sakaino Formation, Tanjosan Tuff Breccia
• Intruded by: Shitodani Granite, Granite porphyry dike, Diorite porphyry dike, Diorite dike

• Sedimentary facies (Upper): Pyroclastic flow deposit
• Sedimentary facies (Middle): Lacustrine
• Lithofacies (Upper): Biotite rhyolite welded tuff (3 flow units)
• Lithofacies (Middle): Tuffaceous sandstone, Mudstone
• Lithofacies (Lower): Biotite rhyolite welded tuff
• Lithofacies (Lower, Minor): Tuff breccia
• Sedimentary structures (Upper): Cooling joint

• Thickness (Upper): 700 m or thicker
• Thickness (Lower): ca. 600 m
• Distribution (Length): ca. 21 km
• Distribution (Width): ca. 9 km
• Upper limit: Unconformity (Toishigawa Mudstone and Sandstone Member)
• Lower limit: Unconformity (Kamogawa Formation, Akusa Formation)

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

• Distribution: Hiraki - Akitsu, Kato city, Hyogo pref.; Konda town - Nakahata - Hiraki mine, Nishiwaki city, Hyogo pref.; Ishido, Kaibara town, Tamba city, Hyogo pref.; Kitaota - Kanaya, Sannaan town, Tamba city, Hyogo pref.; Ajima - Furuichi, Tannan tonw, Tambasasayama city, Hyogo pref.; Shitodani, Konda town, Tambasasayama city, Hyogo pref.; Okawase, Sanda city, Hyogo pref.

• Kurimoto et al. (1993) Geology of the Sasayama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 93p. (in Japanese with English abstract 5p.)
• Ozaki and Matsuura (1988) Geology of the Sanda District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 93p. (in Japanese with English abstract 5p.)