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Tsuzurao Formation Yamauchi et al., 2009

Invalid synonym: Tsuzurao Caldera, Tsuzurao Cauldron

• Type locality: Fusenakatani, Okinoshima city, Oki county, Shimane prefecture
• Volcanic rocks
• Collapse caldera
• Miocene - Pliocene (5.45 Ma, K-Ar)
• Intruded by: Feeder rhyolitic dike, Minamidani Basalt, Trachyte dike (Tokage-iwa), Basalt dikes
• Intruded in (Volcanic vent): Tokihariyama Formation

• Sedimentary facies: Volcanic edifice
• Sedimentary facies (Minor): Volcanic vent rhyolitic dike
• Lithofacies (Upper): Rhyolitic tuff breccia, Lapilli tuff
• Lithofacies (Upper, Minor): Welded tuff, Volcanic vent breccia
• Lithofacies (Lower): Rhyolite lava
• Lithofacies (Basal, Minor): Breccia
• Lithofacies (volcanic vent): Breccia

• Thickness: 940 m
• Thickness (Upper): ca. 30 - 300 m
• Thickness (Lower): ca. 130 m
• Thickness (Basal): 25 - 30 m
• Distribution: 6 x 4.5 km²
• Distribution (Volcanic vent, Width): 400 m
• Distribution (Volcanic vent, Length): ca. 1,500 m
• Upper limit: Unconformity (Mukogaoka Formation)
• Lower limit: Abut unconformity (Tokihariyama Formation, Oki Metamorphic Rocks, Dogo-Minamidani Granite)

• Distribution: Mount Tsuzuraoyama, Okinoshima city, Oki county, Shimane pref.

• Yamauchi et al. (2009) Geology of the Saigo District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 118p. (in Japanese with English abstract 3p.)