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CGC-08 Reconstruction of past climates based on combinations of microfossil records
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Asian monsoon variability recorded by terrestrial mollusk assemblages in the Chinese loess plateau since the last 500 ka
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Naiqin Wu, Institute of Geology and Geophysics, Chinese Academy of Sciences (China)
Xiaoyun Chen, Institute of Geology and Geophysics, Chinese Academy of Sciences (China)
Fengjiang Li, Institute of Geology and Geophysics, Chinese Academy of Sciences (China)
Denis-Didier Rousseau, Ecole Normale Superieme de Paris (France)
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Two loess sections in the Loess Plateau of China have been studied to characterize the variations of the East Asian monsoon climate since the last 500 ka of the Quaternary period. A general climate change trend, indicated by the variations in abundance of land mollusc species, is a gradual cooling and drying during the past 500 ka. Systematic fluctuations in thermal-humidiphilous mollusk type indicate that the strength of the SE Asian summer monsoon is sensitive to orbital forcing at the obliquity and precession periods (41 and 23 ka, respectively).
While the cold-aridiphilous mollusk variability displays a different pattern. The strongest powers are centered at about 100 ka, which drive the major period of winter monsoon variations in the Chinese loess. Both mollusk records from the Xifeng and Luochuan loess sections reveal three particular strengthened summer monsoon events occurred during L5, L4 and L2 glacials. The strongest summer monsoon occurred in L5, indicating by the most abundance of G. armigerella, and secondary L4 and L2. The mechanisms caused these events may be attributed to particular astronomical configurations leading to increased summer insolation gradient between the tropics and the high latitudes.
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