| Project/Area Number |
09839041
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
自然史科学
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| Research Institution | NATIONAL SCIENCE MUSEUM |
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Principal Investigator |
SAITO Yasuji Department of Geology, National Science Museum, Director, 地学研究部, 部長 (00000133)
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| Co-Investigator(Kenkyū-buntansha) |
TANIMURA Yoshihiro Department of Geology, National Science Museum, Chief, 地学研究部, 室長 (80141985)
MATSUBARA Satoshi Department of Geology, National Science Museum, Chief, 地学研究部, 室長 (40000137)
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| Project Period (FY) |
1997 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1999: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1998: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1997: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | bedded chert / siliceous shale / biogenic silica / radiolaria / diatom / ocean circulation / 珪質堆積岩 / チャート / 硬質頁岩 / ポーセラナイト / 珪藻土 / シリカ収支 |
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| Research Abstract |
Sedimentary rocks characterized by high silica content were geologically investigated in relation to paleoceanographical reconstruction. They occur in the circum-Pacific orogenic belts. In Japanese Islands, late Paleozoic and Mesozoic bedded chert, Tertiary siliceous shale (so-called hard shale), and diatomite are the representatives of the siliceous sedimentary rocks. They consist mostly of such siliceous microfossils as radiolarian remains, siliceous sponge spicules and diatom frustules and contain no detrital coarse-grained clastics. These facts show that the siliceous rocks are of biogenic origin and were formed in pelagic to hemi-pelagic environment. And the contents of biota are most important for estimation of nature of ocean water-mass and for reconstruction of global ocean circulation in geohistory. Triassic and early Jurassic cherts embedded as exotic blocks in the Jurassic accretion complex, Chichibu, Ashio, and Mino-Tanba belts, are regarded as a sign of high productivity of marine siliceous plankton possibly in tropical to subtropical zone of the Panthalassa. Cretaceous chert in the Cretaceous to Tertiary accretion complex, Shimato Belt, is related to the formation of equatorial current as a result of the breakup of supercontinent Pangaea. Tertiary, mainly middle Miocene, siliceous shale and diatomite distributed in Sea of Japan side were accumulated under the influence of cold saline deep water. The cold deep water was related to the formation of Antarctic circumpolar current due to the opening of Drake passage and the isolation of the Antarctic Continet. Uneven distribution of siliceous sedimentary rocks in geohistory is considered to reflects plate reorganization and change in global ocean circulation and in productivity of marine siliceous microbiota.
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