关于东亚季风演变的问题讨论

A DISCUSSION ON THE EVOLUTION OF EAST ASIAN MONSOON

评述了有关亚洲季风形成时代的主要观点，根据晚新生代青藏高原阶段性隆起和亚洲自然环境的演变，将亚洲季风的形成过程划分为无季风、准季风、海洋型季风和大陆型季风４个阶段。大陆型季风即现代季风，它是第四纪中期青藏高原隆起达到３０００ｍ以上的产物，因为亚洲中部温带沙漠出现、典型风成黄土普遍堆积、网纹红土发育、动植物群转型等均发生在１．２ＭａＢ．Ｐ．左右。指出青藏高原隆起过程中的非线性气候效应，是古海洋型季风向现代大陆型季风转变的主要动因。

According to the evolution of natural environment and the uplift of Qinghai Xizang(Tibet)Plateau in the Late Cenozoic,the author points out that the formation processes of East Asian monsoon can be divided into four stages:(1)Monsoon free:before the uplift of the plateau in Eogene,there was no monsoon circulation,therefore the climate at that time should have been controlled by planetary winds.(2)Quasi monsoon stage:in Neogene when the plateau reached about 1000m asl,the position and area of the Eurasia were as same as those at present,and the quasi monsoon in this area could begin to form at that time.(3)Marine monsoon stage:in Early Quaternary the average height of Qinghai Xizang Plateau was about 2000m asl,which made the summer monsoon of the East Asia stronger,and the climate in the area at that time was warmer and moister than today.(4)Continental monsoon stage:at 1 2MaB.P. Qinghai Xizang Plateau reached about 3 000m asl,and mountains in the plateau reached about 4 000 ? ? 000m asl,which made the winter monsoon stronger than the summer monsoon in the East Asia.The environmental evolution in the area tended to be drier and colder,and the present circulation pattern of the continental monsoon in the area has formed since the Mid Quaternary.The monsoon desert in NW China came into being during 1 2MaB.P. as a result of a“twin relationship” between desert and loess.Since then the typical eolian loess in Loess Plateau,called“Lishi loess”and“Malan loess”,began to deposit under the conditions of the winter monsoon and the westlies.At the same time,the vermiculated red soil and the rainstorm mud rock flow also began to form.They prove that the continental monsoon in East Asia began to occur from Mid Quaternary.