2007 Fiscal Year Final Research Report Summary
Reconstruction of Paleoenvironmental Changes using Radionuclides:Uranium and Thorium Isotopes in the Lake Sediments
| Project/Area Number |
18510008
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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 |
Environmental dynamic analysis
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| Research Institution | Kanazawa University |
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Principal Investigator |
YAMAMOTO Masayoshi Kanazawa University, K-INET, Professor (10121295)
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| Co-Investigator(Kenkyū-buntansha) |
KASHIWAYA Kenji Kanazawa University, K-INET, Professor (30161029)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Lake Hovsgol / Lake Baikal / Paleoclimatic change / Paleoenvironmental change / Lake sediments / Uranium / Thorium / Geochemical behavior |
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| Research Abstract |
Investigation on polar ice-sheet and lake sediments of mide-latitude area have made studies on past climatic and environmental conditions in continental areas very important to obtain a more information cu mechanisms of Quaternary environmental changes. In Lake Baikal in southeastern Siberia, the dear signal of changing paleoclimate in the sediments has been found in depth distributions of the diatom frustule numbers, water content and organic carbon content in sediments. Furthermore, microelements, especially, uranium have been also noticed as one of the most important chemical index. Thus, the U (and Th) isotopes in lacustrine sediments serve as good proxies for not only chronology but also indicator of climatic changes. Jake Hovsgol, the largest fresh water lake in Mongolia, promiePa the sensitive response to environmental changes in surrounding catchments. In this study, an attempt was made to get a detail feature of U and Th isotopes distribution in the sediment core of Lake Hovsgol. The obtained data were discussed laying stress on dating using 238U-234U-230Th-232Th system, and compared with those obtained previously in sediments core fit Lake Baikal The final purpose of this study was to elucidate the changes in the depth distribution of U and Th isotopes and their ratios in the sediments ad to obtain insight into their implication for paleoclimatic variation.
1. Depth profiles of U and Th isotopes in a 81 m length sediment core (HDP-04) of Lake Hovsgol were measured in details, and U-series isochron techniques were successfully applied to the dating for some layers.
2. The depth distribution of authigenic U well correlated with that of bio-marker of primary products, suggesting that the fluctuation of authigenic U well correlates with glacial-interglacial cycle at least about IMa.
3. A similar pattern of u depth profiles in sediments was observed in the dated depth from 24 m to surface in Lake Hovsgol and lake Baikal with quite different water qualities.
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Research Products
(19 results)
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[Presentation] Uranium and thorium isotopes in lake sediments-lake Biwa system in Japan : To obtain insight into their paleoenvironmental implications2006
Author(s)
Sakaguchi, A., Yamamoto, M., Tomita, J., Kofuji, H., Aota, Y., Yokota, K., Kumagai, M
Organizer
3rd Korea-Japan Joint International Workshop on Present Earth Surface Processes and Historical Environmental Changes in East Asia
Place of Presentation
Seoul
Year and Date
20060926-30
Description
「研究成果報告書概要(欧文)」より
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