阿尔金山及其毗邻地区构造地貌的形成和演化

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

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。

Tectonic landforms;fauly zone; Neotectonic stress field;Development mechanism; Evolution process Abstract The Altun Mountain on the northwest of the Qinghai-Xizang Plateau is a fault-blockmountain, and the gemorphic pattern of the tectonic landforms in this region looks much likea flat alphabet“S”.We found that the Altun fault zone which reactived during the period ofNeotectonic movemnt was playing an important role in the development of tectonic landformsin 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 geomor-phic pattern of this region was also formed under the stress field at that time. As a result,thearc fauly-block mountains and fault basins are distributed antisymmetrically to the AItunstrik-slip fault zone.Based on the synthetical analysis of the Quaternary strata, tectosequent and absolute agedata, the evolution process of tectonic landrorms in this region can be divided into threestages. 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 theHolocene(0.25Ma.B.P. to the present).Considering the time sequence,the evolution processof tectonic landforms in this region was in conformity woth that of the Qinghai-XizangPlateau. It was since the late Pleistocene,i.e., since 0.25Ma,B.P., when the Tarim Basinwas really separated from the Caidam Basin by the Altun Mountain, As the uplifting activi-ties and the development of the AItun fault-blocks showed strong in the west and weak inthe East these processes produced the present undulating shope of the AItun Mountain.