| Project/Area Number |
15540448
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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 |
Stratigraphy/Paleontology
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| Research Institution | Chiba University |
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Principal Investigator |
KAMEO Koji Chiba University, Marine Biosystems Research Center, Assistant professor, 海洋バイオシステム研究センター, 助手 (00312968)
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| Co-Investigator(Kenkyū-buntansha) |
KOTAKE Nobuhiro Chiba University, Faculty of Sciences, Associate professor, 理学部, 助教授 (00205402)
MOTOYAMA Isao Tsukuba University, Department of Earth Sciences, lecturer, 地球科学系, 講師 (80295295)
IWAI Masao Kochi University, Faculty of Sciences, Associate professor, 理学部, 助教授 (90274357)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2004: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2003: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Keywords | calcareous nannofossils / diatoms / radiolarians / trace fossils / calcareous concretion / 放散虫化石 / ノジュール |
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| Research Abstract |
The qualitative analyses of microfossils and trace fossils from the Neogene and the Quaternary sections distributed in the Pacific side of Japan and related deep sea core sediments were performed to determine changes in surface circulation systems in the North Pacific and changes of deep sea environments, and implications for climatic changes. Stratigraphic occurrences of two characteristic taxa of nannofossils and diatoms in the Choshi area allow us to monitor the movement of the oceanographic front around the NW Pacific. Floral changes can be strongly related to the circulation changes around the North Pacific Ocean. For example, at approximately 0.85 Ma, the Oyashio Current, a cool and nutrient-rich surface current in the NW Pacific, suddenly invaded into the Pacific side around the Japanese islands. The timing of this strong invasion of the Oyashio Current coincides with the initial event of the mid-Pleistocene Transition (MPT;0.90〜0.60Ma), corresponding to the transition time to high frequnecy ice volume fluctuation during the late Pleistocene (e.g.Raymo,1990). This means that the oceanographic frontal system along the NW Pacific has been controlled by global climate change occurred in the high latitude during the middle Pleistocene. At the same time, activities of benthic organisms and developments of calcareous concretion layers had become stronger and thus, these results suggest that the subtropical gyre circulation in the North Pacific region had changed and deep sea circulations also altered. During the Miocene, same phenomena were also found and thus, flux changes of primary producers affected ocean climatic changes.
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