西藏吉隆—沃马盆地龙骨沟剖面古地磁年代学及喜马拉雅山抬升记录

PALEOMAGNETIC CHRONOLOGY AND RECORDS OF HIMALAYAN UPLIFT ON THE LONGGUGOU SECTION OF GYIRONG-OMA BASIN IN XIZANG(TIBET)

研究了西藏吉隆—沃马盆地龙骨沟剖面新近纪沉积环境 ,作了古地磁年代学研究 ,认为喜马拉雅山北坡新生代断陷盆地发育始于 7.2MaB .P .,3.2MaB .P .湖盆萎缩消亡 ,标志着喜马拉雅山地区在 7.2MaB .P .和3.2MaB .P .发生过强烈的隆升事件 .沃马盆地龙骨沟剖面所含三趾马动物群化石层年龄大约为 7.0～ 6 .7MaB .P .,隐示着此时青藏地区三趾马生活区与当时的华北平原三趾马生活区有着大体相当的地理、气候环境 .之后由于喜马拉雅山持续抬升 ,断陷盆地下沉 ,并在 5 .9～ 3.6MaB .P .期间湖盆面积最为广阔 .青藏高原抬升而华北平原沉降 ,中国西部地区地形高于东部 ,东西部气候环境发生重大差异 .3.6MaB .P .由于青藏地区持续强烈隆升 ,西部地区河流切穿古老湖盆 ,3.2 0MaB .P .吉隆—沃马湖盆萎缩 ,于 1.7MaB .P .逐渐消失 。

We study the Neogene sedimentary environment of the Longgugou section in the Gyirong-Oma Basin, Xizang (Tibet) by means of paleomagnetic chronology. Analogy shows that Cenozoic fault-bounded basin on the north slope of Himalayas formed by 7.2MaB.P. And it shrank and died 3.2 MaB.P. It marked that the region around the Himalayas had experienced intensified uplift covering the interval from 7.2 to 3.2MaB.P. The age of Hipparion fossils localitied in the Longgugou section is about 7.0～6.7MaB.P. In comparison with Hipparion fauna in North China, they should have similar geographic and climatic environment. Since the continual rise of the Himalayas, the fault-bounded basin subsided and the lake-basins attainted the biggest area during the period of 5.9～3.6 MaB.P. With the uplift of the Qinghai-Xizang Plateau and the subsidence of plain of North China, the topography of the west became higher than that of the east, and there had occurred great change in climatic environment between these two regions. For the reason of continually intensified uplift of Qinghai-Xizang 3.6MaB.P., the rivers in the west region cut through the ancient lake-basins and the lake basin of Gyirong-Oma contracted 3.2 MaB.P., died out 1.7 MaB.P., and then stepped into the stage of erosion and dissection.