1995 Fiscal Year Final Research Report Summary
Reconstruction of the aridity in Central Asia during Quaternary and its relation to the variation in atmospheric circulation
| Project/Area Number |
05405002
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
広領域
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| Research Institution | The University of Tokyo |
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Principal Investigator |
TADA Yruji The University of Tokyo, Graduate School of Science, Associate Professor, 大学院・理学系研究科, 助教授 (30143366)
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| Co-Investigator(Kenkyū-buntansha) |
TAJIKA Eiichi The University of Tokyo, Graduate School of science, Research Associate, 大学院・理学系研究科, 助手 (70251410)
NAKASHIMA Satoru The University of Tokyo, Graduate School of Science, Associate Professor, 大学院・理学系研究科, 助教授 (80237255)
KOIZUMI Itaru Hokkaido University, Graduate School of Science, Professor, 大学院・理学研究科, 教授 (20029721)
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| Project Period (FY) |
1993 – 1995
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| Keywords | Central Asia / aridity / Kosa / Japan Sea / Quaternary / Dansgaard-Oeschger Cycle / Flux |
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| Research Abstract |
In this research project, we used drilling core samples of the Japan Sea sediments and 1) analyzed carbonate carbon, organic carbon and biogenic opal contents to quantify detrital content within each samples, and 2) analyzed major element composition of the samples to which we performed Q-mode factor analysis to derive 4 major detrital sub-components, estimate their chemical composition and contents of each sub-components within each samples. We also analyzed mineral composition of the samples and performed multiple regression analysis of them to the 4 derived detrital sub-components to estimate mineral composition of the each sub-components. 3) We, then, compared the estimated chemical and mineral compositions of the sub-components with the compositions of Kosa, Loess and terrigenous material derived from the Japan Arc to identify the origin of the sub-components, and 4) construct detailed age model based on diatom abundance and tephra chronological data to calculate mass accumulation
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rates of each sub-components. Based on these data, 5) we reconstructed variation of the Kosa flux to the Japan Sea during the last 800 ka with the time resolution of 5 ka, and for the last 200 ka is with the time resolution of 0.7 ka. The result suggests a) Kosa flux to the central Japan Sea varies within the range of 1 to 2 g/cm2/ky and there is a tendency of higher Kosa flux during glacial periods and lower flux during interglacial periods in general, b) however, such tendency is obvious only to long lasting glacial and interglacial periods, c) Kosa fraction variation pattern during the last 200 ka correlatable to millennial-scale abrupt climatic changes known as Dansgaard-Oeschger cycle, d) the intervals of lower contribution of Kosa agree well with the periods of East China Sea coastal water intusion to the Japan Sea deduced from diatom assemblage. The increasing influence of the East China Sea coastal water suggests increasing contribution of discharge from the Huanguhe and Changchiang Rivers due to the increasing precipitation within the central Asia, which is in agreement of lower Kosa fraction durin these periods. The Dansgaard-Oeschger cycles manifested as the variation in Kosa fraction could imply millennial scale wet and dry cycles in the central Asia. Less
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