[ Top ] [ Japanese ]

Maruberiwan Formation Umino, 1985

• Type locality: Chihiroiwa, Maruberi bay, Chichijima, Ogasawara city, Tokyo
• Volcanic rocks
• Eocene (44.5 - 42.8 Ma, Radiolarians; 48.1 Ma, K-Ar; 48 - 46 Ma, Ar-Ar)
• Intruded by: Boninite, Andesite, Dacite, Quartz-bearing dacite, Rhyolite dikes

• Lithofacies (Upper): Hypersthene augite dacite pillow lava
• Lithofacies (Middle): Boninite, Bronzite andesite hyaloclastite, Tuff breccia, Scoria tuff
• Lithofacies (Lower): Boninite pillow lava
• Lithofacies (Minor): Bronzite andesite pillow lava, Dacite lava dome, Conglomerate, Interbedded mudstone and sandstone

• Thickness: 710 m or thicker
• Upper limit: Unconformity (Minamizaki Formation, Asahiyama Formation), Abut unconformity (Mikazukiyama Formation)
• Lower limit: Unconformity (John Beach Volcanics)

• Distribution: Chichijima island - Anijima island - Higashijima island - Nishijima island - Hyotanjima island - Hitomarujima island, 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.)