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Fundamental studies on variations of uranium and thorium isotopes in Lake bottom sediment core and their application to the paleoenvironmetal changes

Research Project

Project/Area Number 16510005
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Environmental dynamic analysis
Research InstitutionKanazawa University

Principal Investigator

YAMAMOTO Masayoshi  Kanazawa University, Institute of Nature and Environmental Technology, Professor, 自然計測応用研究センター, 教授 (10121295)

Co-Investigator(Kenkyū-buntansha) KASHIWAYA Kenji  Kanazawa University, Institute of Nature and Environmental Technology, Professor, 自然計測応用研究センター, 教授 (30161029)
Project Period (FY) 2004 – 2005
Project Status Completed (Fiscal Year 2005)
Budget Amount *help
¥3,900,000 (Direct Cost: ¥3,900,000)
Fiscal Year 2005: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2004: ¥2,800,000 (Direct Cost: ¥2,800,000)
KeywordsClimate change / Environmental change / Lake sediments / Uranium and thorium isotopes / Lake Baikal / Sedimentary behavior / Sedimentation rae / Paleoclimate / 古環境解析 / 環境変動 / 堆積速度 / 年代測定 / 流域変動
Research Abstract

The core VER98st.6 taken from the northern part of the Academician Ridge of the Lake Baikal, Siberia, was measured for U and Th isotopes (U-238, U-234, Th-232 and Th-230). Physical and chemical parameters such median grain size and Bio-Si content were also measured. By using the orbital tuning method based on the median grain size fluctuation, the sediment core covers the last two to four interglacial stages, ca.20 ky and is characterized by low sedimentation rate, ca.4.7 cm/ky. The concentration of U-238 fluctuates by a factor of 4,ranging from 50 to 200 Bq/kg. The U-238 concentration displays the higher values during the warm intervals, accompanied by high accumulation of Bio-Si, and the lower values during the cold intervals. The variation of U-234/U-238 ratios is similar to the variation of U-238 concentrations throughout the core. The Th-232 concentration varies in a narrow range, only by a factor of 2. The low Th-232 contents characterize the diatom-rich intervals during the warm intervals. The profile of Th-232 flux correlates well with that of mineral flux, indicating that Th is a proxy for terrestrial materials. The discrimination of the U-238 into the authigenic and terrigenous U-238 fractions reveals that the authigenic U-238 fraction is very low during the periods of glacial intervals, especially being almost zero during MIS 6. The authigenic U in sediments is candidate for the climate-sensitive processes. Based on the U-234-U-238 and Th-230-U-238 dating methods using the estimated authigenic U-238, U-234 and Th-230 contents in sediments during the warm intervals, mean sedimentation rates are independently estimated as 3.84±0.43 and 4.71±0.21 cm/ky respectively. These rates are close to a mean rate of 4.7 cm/ky calculated by the orbital tuning method.

Report

(3 results)
  • 2005 Annual Research Report   Final Research Report Summary
  • 2004 Annual Research Report
  • Research Products

    (9 results)

All 2006 2004 Other

All Journal Article (9 results)

  • [Journal Article] Uranium and thorium isotope distribution in an offshore bottom sediment core of the Selenga Delta, Lake Baikal, Siberia2006

    • Author(s)
      A.Sakaguchi, M.Yamamoto, et al.
    • Journal Title

      J.Paleolimnology 35・4(accepted, issued in May,2006)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2005 Final Research Report Summary
  • [Journal Article] Uranium and thorium isotope distribution in an offshore bottom sediment core of the Selenga Delta, Lake Baikal, Siberia2006

    • Author(s)
      A.Sakaguchi, M.Yamamoto, et al.
    • Journal Title

      J.Paleolimnology 35・4 (accepted, soon issued) (発表予定)

    • Related Report
      2005 Annual Research Report
  • [Journal Article] Information from uranium and thorium isotopes recorded in lake bottom sediment : Attempt to evaluate environmental changes2004

    • Author(s)
      A.Sakaguichi, M.Yamamoto, et al.
    • Journal Title

      Radioecological and Environmental Dosimetry (Eds.J.Inaba, H.Tsukada, A.Takeda)(Inst.Environmental Sciences, Japan)

      Pages: 348-353

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2005 Final Research Report Summary
  • [Journal Article] Geochemical record of U and Th isotopes in bottom sediments of Lake Kawaguchi at the foot of Mt. Fuji, Japan2004

    • Author(s)
      A.Sakaguchi, M.Yamamoto, et al.
    • Journal Title

      J.Radioanal.Nucl.Chem. 262

      Pages: 617-628

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2005 Final Research Report Summary
  • [Journal Article] Information from uranium and thorium isotopes recorded in lake bottom sediment : Attempt to evaluate environmental changes.2004

    • Author(s)
      A.Sakaguchi, M.Yamamoto, et al.
    • Journal Title

      Proceedings of Radioecological and Environmental Dosimetry (Eds. J.Inaba, H.Tsukada, et al.) (Inst.Environmental Sciences, Japan.)

      Pages: 348-353

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2005 Final Research Report Summary
  • [Journal Article] Geochemical record of U and Th isotopes in bottom sediments of Lake Kawaguchi at the foot of Mt.Fuji, Japan2004

    • Author(s)
      A.Sakaguchi, M.Yamamoto, et al.
    • Journal Title

      J.Radioanal.Nucl.Chem. 262

      Pages: 617-628

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2005 Final Research Report Summary
  • [Journal Article] Information from uranium and thorium isotopes recorded in lake bottom sediment : Attempt to evaluate environmental changes2004

    • Author(s)
      A.Sakaguchi, M.Yamamoto, K.Ishikawa, K.Kashiwaya, Y.Otsuka, K.Yokota
    • Journal Title

      Proceedings of the International Symposium on Radioecology and Environmental Dosimetry(J.Inaba, H.Tsukada, A.Takeda, Eds.), Rokkasho, Aomori, Japan, October 22-24,2003,Institute for Environmental Sciences, Japan

      Pages: 348-353

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Geochemical record of U and Th isotopes in bottom sediments of Lake Kawaguchi at the foot of Mt.Fuji, Japan2004

    • Author(s)
      A.Sakaguchi, M.Yamamoto, T.Shimizu, S.Koshimizu
    • Journal Title

      J.Radional.Nucl.Chem. 262

      Pages: 617-628

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Uranium and thorium isotope distribution in an offshore bottom sediment core of the Selenga Delta, Lake Baikal, Siberia

    • Author(s)
      A.Sakaguchi, M.Yamamoto, et al.
    • Journal Title

      J.Paleolimnology (soon issued)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2005 Final Research Report Summary

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Published: 2004-04-01   Modified: 2016-04-21  

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