| Project/Area Number |
11304032
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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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., Div. Earth and Planetary Sciences, Professor, 大学院・理学研究科, 教授 (80111334)
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| Co-Investigator(Kenkyū-buntansha) |
JORDAN Richard Yamagata Univ., Dept. Earth Environement Associate Professor, 理学部, 助教授 (90260455)
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| Project Period (FY) |
1999 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥32,940,000 (Direct Cost: ¥31,200,000、Indirect Cost: ¥1,740,000)
Fiscal Year 2002: ¥2,860,000 (Direct Cost: ¥2,200,000、Indirect Cost: ¥660,000)
Fiscal Year 2001: ¥4,680,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥1,080,000)
Fiscal Year 2000: ¥4,700,000 (Direct Cost: ¥4,700,000)
Fiscal Year 1999: ¥20,700,000 (Direct Cost: ¥20,700,000)
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| Keywords | western Pacific Warm Pool / Calcareous nannoplankton / Coccolith / Carbonate Flux / Watermass / ENSO / フラックス |
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| Research Abstract |
We have studied the three dimensional distribution of calcareous nannoplankton in the Western equatorial Pacific and have identified, 1) the flora differs across the thermocline in the high-temperature water, warm eutrophic water and warm oligotrophic water regimes, but 2) no floral difference can be seen in the temperate mixed-water regime. By analyzing 485 tropical and subtropical Pacific surface-water samples including 351 samples collected by the Lamont-Doherty Earth Observatory, we have identified seven different floras correlating to different surface trophic levels. The distribution pattern of these floras clearly correspond to the longitudinal gradient in the surface nutrient level, and was the first observation of the longitudinal distribution in nannoplankton flora in a pelagic environment. We have also reported unusual concentration of very small placoliths in a tropical upwelling waters and have indicated paleoceanographic usefulness of these very small taxa.
For the multi-year study of seasonal variations of calcareous nannoplankton in the tropical Pacific using the sediment-trap samples, we have obtained continuously the transition from La Nina to El Nino phases. Although the last batch of samples were just recovered and the analysis is continuing, we are now sure that the Molfino and Mclntyre (1991) Model that is widely used for paleoceanographic reconstructions does not work in the tropical Pacific where the nutricline is quite deep. A new methodology was proposed for a quantitative study of nannofossils in sediment samples, and by using this new technique we have analyzed several Quatemary cores for hgih-resolution paleoceanography.
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