Sedimentary fills of Izu-Bonin fore-arc and back-arc rift basins south of Japan, ODP Leg 126
- Univ. of Illinois, Chicago (USA)
- Universita della Calabria, Scalo (Italy)
- Memorial Univ., St. John's, Newfoundland (Canada)
- Texas A and M Univ., College Station, TX (USA)
- Univ. of Texas, El Paso (USA)
- Geological Survey of Japan, Ibaraki (Japan)
- Shimane Univ., Matsue (Japan)
- Univ. of California at Santa Cruz, CA (USA)
- Tohoku Univ., Aoba (Japan)
- Univ. of Tokyo (Japan)
- Hawaii Institute of Geophysics, Honolulu (USA)
From April to June 1989, Leg 126 of the Ocean Drilling Program successfully drilled the Izu-Bonin intraoceanic arc: Sites 787, 792, and 793 in the eastern, western, and central portions of a 40-70-km-wide fore-arc basin; Sites 790 and 791 on the 2-km-deep floor of the Sumizu back-arc rift; and Site 788 on the eastern rift footwall. Basaltic andesite and andesite basement of the fore-arc basin, initially 4-5 km deep, was produced by rifting or spreading that started 31-34 Ma (middle Oligocene) and has since been uplifted 1-2 km. Volcanism and erosion of surrounding highs provided debris flows and turbidites that began to fill the basin 250-300 m/m.y. Sharply declining volcanism and epiclastic supply are recorded in slowly accumulated Oligocene-Miocene (24-13 Ma) hemipelagic sediments. Regional explosive volcanism, renewed after 13 Ma, has left more than 200 thin ash layers in the uppermost (late Pliocene-Holocene) sediments. Total basin fill is 1.5-4 km thick. The Sumisu began to form 3.56-1.1 Ma. Prerift and present-day volcanism has been dominated by rhyolitic pumice eruptions. The eastern rift footwall, now 1.1 km below sea level, has been uplifted 0.2-1.7 km. Basaltic and arc-pyroclastic rift basement was 2 km deep prior to 1.1 Ma. From 1.1 to 0.235 Ma, 100-400 m of predominantly hemipelagic sediment were deposited, although intrarift basaltic eruptions and rhyolitic eruptions were fairly common. Explosive arc volcanism increased dramatically 250 Ka, leaving 165-428 m of fine to coarse pumiceous sediments in layers that are each 30-50 m thick at Site 790.
- OSTI ID:
- 6638164
- Report Number(s):
- CONF-900605-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 74:5; Conference: Annual convention and exposition of the American Association of Petroleum Geologists, San Francisco, CA (USA), 3-6 Jun 1990; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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