| Project/Area Number |
11691113
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 海外学術 |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
OKADA Hisatake Hokkaido Univ., Grad. School of Sci., Prof., 大学院・理学研究科, 教授 (80111334)
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| Co-Investigator(Kenkyū-buntansha) |
NISHI Hiroshi Kyusyu Univ., Grad. School of Social Cult. Stud., Asso. Prof., 大学院・比較社会文科研究科, 助教授 (20192685)
KAWAHATA Hotaka Tohoku Univ., Grad. School of Sci., Prof., 大学院・理学研究科, 教授
SAKAMOTO Tatsuhiko Hokkaido Univ., Grad. School of Sci., Inst., 大学院・理学研究科, 助手 (90271709)
HASEGAWA Takashi Kanazawa Univ., Fac. of Sci., Inst., 自然科学研究科, 助手 (50272943)
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| Project Period (FY) |
1999 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥11,700,000 (Direct Cost: ¥11,700,000)
Fiscal Year 2001: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2000: ¥4,900,000 (Direct Cost: ¥4,900,000)
Fiscal Year 1999: ¥5,700,000 (Direct Cost: ¥5,700,000)
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| Keywords | Cretaceous / OAE / Balck Shale / Paleoceanography |
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| Research Abstract |
We have studied the geology and sampled Ocean Anoxic Event sequences in SE France from the Goguel (OAE1a) and Killian to Paquir (OAE1b) intervals. In addition, we recovered three 8m long cores from the upper-most level of OAE1b sediment. The genetic analysis of endolithic bacterial relics for this core has revealed a high concentration of rDNA clones of oceanic sulfate-reducing bacteria (SRB) within δ-Proteobacteria predominated. The phosphate rich bed in this core is likely to be deposited at the sea floor where cold seepage developed. At the Killian and Paquir levels, the abundance of calcareous nannofossils decreased significantly and Nannoconus suddenly dominated the species assemblage. Nannoconus is postulated as a lower-photic zone dweller. Because the dissolution of coccolith is not a significant factor in the studied sequence, these observations clearly indicate a major change in the primary producing community during the deposition of OAE1b black shales. From the nannofossil biostratigraphy, the time needed to deposit the Paquir level was estimated as ca. 50 Kyrs. A X-ray analysis of the shaly beds revealed an alternation of fine lamina consisting foraminifera-rich layers and clay-rich layers. The latter is also characterized by a higher concentration of organic matter. A high-resolution (1 cm interval) analysis of calcareous nannofossil assemblage in the Paquir level shows a general dominance of Nannoconus and repeated occurrence of very short intervals where the taxa decreased its abundance dramatically. These evidences indicate, 1) vertical mixing of water column was generally reduced during the deposition of OAE1b black shales, 2) but the environment had returned to normal mode during several short intervals within the time of Paquir deposaition.
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