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Mikazukiyama Formation (Umino, 1985) Umino and Nakano, 2007

• Type locality: Mount Mikazukiyama - Cape Onezaki, Chichijima, Ogasawara city, Tokyo
• Volcanic rocks
• Eocene (48.5 - 39.5 Ma, Radiolarians; 45.9 - 43.6 Ma, Foraminifera; ca. 45 Ma, Ar-Ar)

• Sedimentary facies (Upper): Debris avalanche deposit
• Lithofacies: Calc-alkaline series
• Lithofacies (Upper): Hypersthene augite andesite, Dacite tuff breccia, Volcanic breccia, Bronzite-andesite pillow lava
• Lithofacies (Upper, Minor): Interbedded sandstone and mudstone
• Lithofacies (Middle): Conglomerate
• Lithofacies (Lower): Interbedded sandstone and mudstone
• Sedimentary structures (Upper): Cross stratification, Parallel stratification

• Thickness: 300 m or thicker
• Lower limit: Abut unconformity (Maruberiwan Formation, Asahiyama Formation)

• Distribution: Mount Mikazuki - Cape Onezaki, Chichijima, Ogasawara city, Tokyo; Cape Futamata, Anijima, Ogasawara city, Tokyo; Ototojima, Ogasawara city, Tokyo

• Umino and Nakano (2007) Geology of the Chichijima Retto District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 71p. (in Japanese with English abstract 3p.)