关键词: 构造地貌, 走滑断裂带, 新构造应力场, 发育机制, 演化过程

Abstract: 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.

Key words: Tectonic landforms, fauly zone, Neotectonic stress field, Development mechanism, Evolution process