阿尔金山及其毗邻地区构造地貌的形成和演化

在新构造运动中复活的阿尔金走滑断裂带制约着本区构造地貌的分布格局和发育过程.阿尔金山即是该断裂带所控制的断块发生强烈上升而成的差异性断决山地,以阿尔金山为轴成反对称分布的区域地貌格局也是阿尔金走滑断裂带发生大规模左旋平移和逆冲推覆的产物.本区构造地貌演化则经历了三个阶段,其间断块上升活动西强东弱并自西向东发展,因而形成阿尔金山西高东低的起伏形态.

FORMATION AND EVOLUTON OF THE TECTONIC LANDFORMS IN THE ALTUN MOUNTAIN AND ITS NEIGHBOURING REGION

The Altun Mountain on the northwest of the Qinghai-Xizang Plateau is a fault-block mountain, and the gemorphic pattern of the tectonic landforms in this region looks much like a flat alphabet"S".We found that the Altun fault zone which reactived during the period of Neotectonic movemnt was playing an important role in the development of tectonic landforms in this region, That is, the AItun Mountain was formed by the strong uplifting fault-blicks,which took place under the control of the fault zone in the Quaternary, Similarly,the geomorphic pattern of this region was also formed under the stress field at that time. As a result,the arc fauly-block mountains and fault basins are distributed antisymmetrically to the Altun strik-slip fault zone.Based on the synthetical analysis of the Quaternary strata, tectosequent and absolute age data, the evolution process of tectonic landrorms in this region can be divided into three stages. The first stage is from the end of the Pliocene to the early pleistocene(2.80-1.60Ma.B.P.),the second is from the end of the early pleistocene to the mid-pleistocene(1.60-0.25Ma.B.P.), and the third is from the end of the mid-pleistocene to the Holocene(0.25Ma.B.P. to the present).Considering the time sequence,the evolution process of tectonic landforms in this region was in conformity woth that of the Qinghai-Xizang Plateau. It was since the late Pleistocene,i.e., since 0.25Ma,B.P., when the Tarim Basin was really separated from the Caidam Basin by the Altun Mountain, As the uplifting activities and the development of the Altun fault-blocks showed strong in the west and weak in the East these processes produced the present undulating shope of the Altun Mountain.