Acta Geographica Sinica ›› 2008, Vol. 63 ›› Issue (9): 931-944.doi: 10.11821/xb200809004

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Ostracodes Assemblages and Their Environmental Significance from Lake Core of Nam Co, Tibetan Plateau

XIE Manping1,2, ZHU Liping1, PENG Ping1,2, ZHEN Xiaolin2,3,WANG Yong1,2,JU Jianting2,3,A. CHWALB4   

  1. 1. Institute of Tibetan Plateau Research, CAS, Beijing 100085, China;
    2. Graduate University of Chinese Academy of Sciences, Beijing 100039, China;
    3. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China;
    4. Institut für Umweltgeologic, Technische Universität, Braunschweig, Germany
  • Received:2008-04-12 Revised:2008-06-25 Online:2008-09-25 Published:2008-09-25
  • Supported by:

    National Basic Research Program of China, No. 2005CB422002; National Natural Science Foundation of China, No.40571172; 6th EU Framework Program BRAHMATWINN, No.KZCX3-SW-339

Abstract:

A 332-cm long lacustrine core was drilled in the middle south of Tibentan Plateau. From the core, 15 species of ostracodes belonging to 6 genera have been identified. According to the changes of the ostracodes assemblage and the ostracodes ecological characters, which are sensitive to the changed of environment, three stages can be distinguished as follows: The early stage was from 8400 to 6800 aBP, during which the temperature descended in fluctuation which matched with the unstable cooling event of earlier Holocene, the climate was cold-humid, and the lake depth changed from shallow to deep. The middle stage was from 6400 to 2500 aBP, during which the climate changed from warm-humid to cold-humid and then became cold-dry, and the lake depth was becoming deep step by step. Weather pattern shifting during this period, from wet-cold to dry-cold, had been modifying and finally built up modern environments in Nam Co. The late stage (2500 aBP- present) showed a trait of lake depth increasing. At the earlier time of this stage, the climate was still cold-dry, which had the same trend of the end of the middle stage, however, the salinity of the lake increased; at the later time of this stage, the climate showed a general tendency toward cold-dry, as well as the hydrological condition of surface flowing water became faint. The concurrence of black shells percentage and the biggest ostracodes content, as well as the increasing of sedimentary hydrodynamic condition, indicated a post-mortem reworking. The abundance of Candona juvenile shells reflected juvenile mortality as a result of the rapid onset of unfavorable conditions such as catastrophic hydrological condition change.

Key words: Tibetan Plateau, Nam Co, ostracodes, environmental change, lacustrine core