新疆罗布泊地区32.0～9.1 kaB.P.期间的孢粉记录及其古气候古环境演化

A POLLEN RECORD AND THE PALEOCLIMATIC AND ENVIRONMENTAL EVOLUTION IN LOP-NUR,XINJIANG IN 32. 0 ～ 9. 1kaB. P.

新疆罗布泊地区罗北洼地CK-2钻孔的孢粉记录揭示出:32.0～9.1kaB.P.植被演替明显,气候干湿波动显著;晚冰期向全新世过渡期间,气候波动频繁且具突变性。31.98～19.26kaB.P.罗布泊地区处于末次冰期的盛冰期阶段,气候寒冷湿润,冷暖波动频繁,但幅度不大,研究区植被以草原-荒漠草原为主;19.26～13.67kaB.P.气候明显变为温暖干燥,植被以荒漠为主;13.67～12.73 kaB.P.气候冷湿偏干,植被以草原-荒漠草原为主;12.73～9.14kaB.P.气候冷湿与暖干交替频繁,波动幅度较大,植被逐渐由荒漠向草原-荒漠草原过渡。其中,16.45～15.39kaB.P.,14.27～13.67kaB.P.和11.74～11.23kaB.P.之间的冷颤动分别相应于老仙女木、叶仙女木和新仙女木事件;15.39～14.27kaB.P.和12.73～11.74kaB.P.之间的暖期则分别对应于欧洲博令和阿勒罗得暖期;新仙女木事件后的气候具有突变性的特点,10.49kaB.P.前后的暖事件和9.14kaB.P.前后的冷事件,成为全新世早期气候变化的显著特征。孢粉浓度和花粉组合所反映的罗布泊地区晚冰期以来的气候演化同全球性的气候事件具有显著的可比性。

Eastern Xinjiang as an aridest region of China is located at the boundary between the East Asian summer monsoon and the Northern Hemisphere＇s westerly winds. This region is sensitive to the environmental change in the large-scale westerly and monsoonal circulation systems. Some studies have indicated that Late Pleistocene climatic changes in this region were mostly influenced by expansion and contraction of the summer monsoonal circulation. However,this region might have experienced complex pattern of climate change neither a direct response to the westerlies nor to summer monsoon due to the interplay between the subtropical monsoon system and the mid-latitude westerlies. We present lithology and fossil pollen data from a sedimentary core CK-2 drilled from the Luobei Depression （40 °47′N, 91 °03′E ）, Lop-Nur in the Eastern Tarim Basin, Xinjiang, China. The paleoenvironmental and paleoclimatic evolution during the time of ca. 32.0 - 9. lkaB. P. has been analyzed in this paper on basis of the pollen data from core CK-2. Our resuhs reveal that during 31.98 - 19. 26kaB. P. corresponding to Late Glacial Maximum（LGM）, the climate was characterized by cold and humid environment, and varied from cold-humid to warm-arid and fluctuated frequently with little amplitude. The vegetation was dominated by steppe-desert steppe in this area. Later, steppe-desert steppe landscape under cold-humid condition was replaced by desert vegetation under a generally warm-arid climate from ca. 19.26kaB. P. to 13.67kaB. P. During the period from ca. 13.67kaB. P. to 12. 73kaB. P.,climate was comparatively cold and semi-humid and steppe-desert steppe prevailed over the area. And through the period from ca. 12. 73kaB. P. to 9. lgkaB. P., climate was varied from cold-humid to warm-arid and fluctuated frequently with large amplitude. The vegetation was changed gradually from desert to steppe-desert steppe in this area. Three cold events in the periods of 16.45 - 15.39kaB. P., 14.27 - 13.67kaB. P. ,and 11.74 - 11.23kaB. P. corresponded to the Oldest Dryas, Older Dryas and Younger Dryas events respectively, whereas the two warm periods between 15.39 - 14.27kaB. P. and 12. 73 - 11.74kaB. P. corresponded to Boiling and Allerod events respectively. After the Younger Dryas event the temperature changed abruptly,and the climate changed from warm at ca. 10. 49kaB. P. to cold at and ca. 9. 14kaB. P., which were the notable characteristics during the early Holocene. Palaeoclimatic evolution and shift events in the Lop Nur region revealed by pollen assemblages and concentrations would be well parallel with the global changes.