日本列島周辺の海底地質 その2. 琉球弧と沖縄舟状海盆(トラフ)
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概要
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The main part of the Ryukyu Arc consists of the Nansei Syoto (Ryukyu) Trench, the Nansei Syoto Ridge and the Okinawa Trough from east to west. The Nansei Syoto Ridge forms a geanticline of the Ryukyu Arc, and the basement of the Nansei Syoto Ridge consists of Paleozoic rocks and the Shimanto Super-group distributed widely in Southwest Japan. Volcanic activities of green tuff developed in the Eocene and Miocene, and they destroyed the framework of the pre-Tertiary structure. After the middle to late Miocene regression in the Nansei Syoto area, widely spread transgression in the late Miocene to early Pleistocene caused deposits of the Shimajiri Group, consisting mainly of sand, mud and pyroclastics. The sedimentary basin of the Shimajiri Group spread over the Nansei Syoto area, including the Okinawa Trough region. Judging from the sedimentary pattern, the construction of the present Ryukyu Arc started during the sedimentation of the Shimajiri Group in the Pliocene. Uplift of the Nansei Syoto Ridge and subsidence of the Okinawa Trough continued in response to the development of the Nansei Syoto Trench. The volcanic activities on the Nansei Syoto Ridge took place in the Pliocene to early Pleistocene and the middle Pleistocene to Holocene. The Okinawa Trough in the Quaternary is active in tectonics. Step faults form the graben structure in the axis of the southwest Okinawa Trough. Some grabens have mid-knolls of basaltic to rhyolitic rocks. Recent hydrothermally active spots with sulfide chimneys and ores can be observed in the central part of the trough northwest of Iheya Sima.
- 日本海洋学会の論文
- 1994-10-30
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- 海の自然史, ティアート・H・ファン・アンデル 著, 水野篤行・川幡穂高 訳, 築地書房, 263p., 1994年, 3605円(税込み)
- 日本列島周辺の海底地質 その2. 琉球弧と沖縄舟状海盆(トラフ)
- 日本列島周辺の海底地質 その1 日本海溝及びその付近