亚洲形变与全球变冷──—探索气候与构造的关系

DEFORMATION OF ASIA AND GLOBAL COOLING:SEARCHING LINKS BETWEEN CLIMATE AND TECTONICS

亚洲是当代地球上唯一夹在两个汇聚大陆边缘的陆地，在亚洲与西太平洋之间由于地形和气压的巨大反差，形成最为强烈的能流和物流。这种反差，是亚洲在新生代晚期经受全球最大构造形变的产物。印度与亚洲碰撞，太平洋板块转向，边缘海张裂，中国地形倒转，大江东流，陆架和沿海平原形成，这一系列变化造成了区域性甚至全球性的严重气候后果。探索亚洲形变与新生代全球变冷的可能关系，从而揭示气候与构造的关系，是我国地学界责无旁贷的任务。

In the modem Earth System , the energy flow and material flow are most active in Asia and Western Pacific. Nearly 20km contrast in toPOgraphy occurs within adistance of only 4000km, betWeen the highest Peak in the World (Qomolangma Fengor Everest 8 848m a.s.l.) and one of the deepest benches in ocean (PhiliPPine Trench,w.d. 10 497m). The world-Wise heating centres at the sea surface level (the WesternPaCific Warm Pool) and at 5 000m a.s.l. (the Tibetan Plateau), as well as the coldestSiberian nigh Cell , all are around thes region. In result the eastern and southern painof Asia with itS islands contribute nearly 70% of the total terrigenous suspended loadtO the global ocean, and the region is also distinguished by the most active wintermonsoon as well as strong tropical cyclones.Asia is the only continent which is sandwiched betWeen two convergentcontinental margins and has experienced the most significant toctonic deformation inthe Cenozoic . It is believed that the India-Asia collision and the NWW tUrn of thePaCific Plate has given rise to the uplift of the Tibetan Plateau on one hand, and tothe formation of the Western Pacific marginal seas on the other. The series of seas,separating the largest conhnent from the largest ocean in the world, have mwhfied themalarial and energy nux betWeen land and ocean, and the evolution of their islandares has led to serious climate consequences. An example is the indonesian Islands,their formation may haVe given rise to the beginning or strengthening of the WesternPacific Wan Pool and the Kuroshio warm crrent Meanwhile, the tectonic changesin the early Miocene led to a reversal of the topographic trend in China fromwest-tilting to east-tilting , with the west-east gradient continuously increasing since then.This explains why the geological records of such large rivers as Changjiang (Yangtze)and Huanghe (Yellow River ) can be theed back only to the Pleistocene .The radical changes in topography of Asia must have profound climate impact,As shown by numerical modeling, the accelerating uplift of the Tibetan Plateau mayhave changed the global atmospheric circulation and hence, have been responsible forthe late Cenozoic global cooling. Moreover, long-term increased chemical erosion inrapidly uplifting areas could reduce atmospheric CO2 and lead to the 'Ice House'regime. On the other hand, the climate pattern in China underwent a reorganization around the beginning of Miocene: the planetary system of atmospheric circulation hasbeen replaced by monsoonal circulation system, and the general pattern has maintainedup to now. The Mid-Cenozoic realignment of the climate pattern in China can beascribed to the India / Asia collision and the increase in size of the Asian continent while the intensified uplift of the Tibetan Plateau should have led to the strengthenedmonsoon system. The hypothetical relationships betWeen the deformation of Asia thelate Cenozoic global cooling, and the evolution of Asian monsoons is to be verifiedby careful studies on continuous stratigraphic sequences both of marine and continental origin .