書誌事項
- タイトル別名
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- Reconstruction of oceanic plate stratigraphies and unit division of Jurassic-Early Cretaceous accretionary complexes in the Okinawa Islands, central Ryukyu Island Arc.
- チュウ リュウキュウ コ オキナワ ショトウ ノ ジュラキ ハクアキ コセイ フカ コンプレックス ニ オケル カイヨウ プレート ソウジョ ノ フクゲン ト ユニット クブン
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The Jurassic-Early Cretaceous accretionary complexes in the Okinawa Islands, central Ryukyu Island Arc, are the southwestern extension of the Southern Chichibu Belt in the Outer Zone, Southwest Japan. They are chaotic sedimentary complexes which consist mainly of greenstone, chert, limestone, sandstone, and mudstone. Microfossil (radiolarian) biostratigraphic study was carried out for the Jurassic accretionary complex, newly called the Iheya unit, in Iheya and Izena Islands, which are in the innermost part of the Southern Chichibu Belt of the Okinawa Islands. A primary sedimentary sequence, that is, an oceanic plate stratigraphy, which consists of the Early to Middle Permian limestone, Late Carboniferous to Middle Triassic pelagic chert, Early Jurassic hemipelagic siliceous mudstone, and Early to Middle Jurassic terrigenous mudstone in ascending order, was reconstructed for the unit. Judging from the youngest age of the stratigraphy, an accretion age of the unit is interpreted to be in the Middle Jurassic.Present study has also resulted in the proposed of a new three-fold division of the Jurassic-Early Cretaceous accretionary complexes in the Southern Chichibu Belt of the Okinawa Islands. This was based on reconstructed oceanic plate stratigraphies compiled from lithologic features and fossil ages of the previous and present works. The three distinct geologic units are as follows : Iheya, Ie, and Motobu units from northwest to southeast or from upper structural horizon to lower one. An accretion age of the Ie unit is inferred to be in the earliest Cretaceous, and that of the Motobu unit to be in the Early Cretaceous, indicating a younging polarity in order of the Iheya unit, Ie unit, and Motobu unit, towards the lower structural units. This subdivision of the accretionary complexes almost coincides with that in the Southern Chichibu Belt of Southwest Japan.
収録刊行物
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- 地質学雑誌
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地質学雑誌 105 (12), 866-880, 1999
一般社団法人 日本地質学会
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詳細情報 詳細情報について
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- CRID
- 1390001206233603072
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- NII論文ID
- 110003013008
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- NII書誌ID
- AN00141768
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- ISSN
- 13499963
- 00167630
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- NDL書誌ID
- 4939283
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- 本文言語コード
- ja
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- データソース種別
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- JaLC
- NDL
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