南极冰盖与中国风尘堆积

ON THE RELATIONSHIP BETWEEN THE ANTARCTIC ICE SHEET AND THE EOLIAN DEPOSITS IN CHINA

通过南极冰盖消长和风尘堆积物的气候事件对比,说明在4.3—2.5 Ma B.P,间南极冰盖增长和北极冰盖发展,中国第三纪风尘红壤土沉积可能是中国东部季风气候雏形形成的反映。2.6Ma以来,随着北极冰盖的迅速扩展,中国内陆进一步干旱化并促成黄土堆积。南极极锋带北移与黄土区极寒等事件的发生具有同步性,据此建立极寒事件的序列,可能反映大气环流强度变化情况。南极东方站冰岩芯气候曲线说明,黄土高原晚更新世以来的干冷期可能形成于0.115Ma B.P.。我国东部地区转暖大致发生在13000aB.P.,此后不久可能出现欧洲新仙女木寒冷事件。此外,大约在40000aB.P.可能有一寒冷事件。

Being a great cold source on the world, the Antarctic Ice Sheet deeply affected the global climatic variation in Quarternary and Pliocene. And, it might have played an important role in the evolution of eolian sedimentation on the Loess Plateau of China. Basing on the comparison of China's eolian sodimentary sequences with the Antarctic Ice Sheet events, including reconstruction of the Antarctic Ice Sheet, northward shifting of the Polar Front Zone, ice rafted debris with a maximum accumulation rate, and sedimentary hiatus in the surroundings since 4.3 Ma B. P., there are some new ideas concluded by the authors. 1. By 3.4 (or 4.3) Ma B. P. the eolian accumulation in China began to deposit down marking the beginning of a primary embryo type of the Monsoon climate. During 4.3—2.5Ma B. P. the developing Antarctic Ice Sheet went on gradually, while the Antarctic Polar Front Zone successively shifted northward, and the climate on the Loess Plateau of China became relative cold and dry, then the eolian red silty dust consequently deposited. It is called the epoch for red silty dust accumulation. 2. When 2.5 Ma B. P. the Arctic Ice Sheet had a fully development. Since then, the shifting frequency of the Antarctic Polar Front Zone increased. The arctic cold source seriously influenced the Loess Plateau of China for eolian accumulation, even subjected to the climatic variations in a global scale. Just this process caused the inland climate of China becoming drier and drier. It may be considered as an epoch for loess accumulation. 3. Since the Late Pliestocene some climatic characteristics of the Loess Plateau and eastern China may be summarized as follows: (1) By the 115 000 a B. P. a dry and cold epoch on the Loess Plateau, corresponding to the end of the antarctic G stage, began to develop. (2) The climatic condition for generation of the first paleosol (S_1) in the last interglacial seemed warmer and more humid than that of Holocene paleosol (S_0). It is similar to that of the Antarctica, though different from those of Europe and some other deep sea-water sediments. (3) During the stage C in Antarctica or the stage 3 in the deep sea., at 42 000 a B, P., there might have been a short cold span in the climate development. The climate in 60 000—50 000 a B. P. seemed rather warmer and more humid than that of 40 000—30 000 a B. P. (4) In the extensive Monsoon regions from China there might have been an abrupt cold event equivalent to that of the Younger Dryas in Europe.