Cenozoic evolution of the Altyn Tagh fault: Evidence from sedimentary records of basins along the fault

Abstract

阿尔金断裂带是青藏高原自印度与欧亚大陆碰撞后向北扩展的前缘断裂，其新生代活动性对于研究青藏高原隆升与扩展过程和机制具有重要意义。近些年，运用热年代学、断裂几何学和运动学、沉积学、磁性地层学和地震学等方法对阿尔金断裂带的性质、组成结构、断裂活动时代、走滑断裂运动特征、走滑位移量和走滑速率等进行了细致的研究，而对阿尔金断裂带沿线受其控制的新生代沉积盆地的地层年代、沉积演化特征虽然也有一定研究，但往往仅限于单个盆地，缺乏对沿线盆地整体的对比认识，造成对阿尔金断裂带走滑起始时间及阿尔金山的隆升历史存在不同的认识。本文对近二十年来阿尔金断裂带沿线新生代沉积盆地的磁性地层年代与沉积相演化的研究进展进行综述，建立阿尔金断裂带沿线盆地新生代沉积序列和年代框架；辅助热年代学等资料，提出阿尔金断裂带的三阶段演化模型:始新世-中中新世，阿尔金断裂带以大幅度的走滑运动为主，同时伴随着阿尔金山小范围的隆升；中中新世开始，阿尔金山开始大规模的隆升，伴随着较少量的走滑运动；晚中新世以来，阿尔金断裂带构造活动加强。;The Altyn Tagh fault is the frontal fault in the expansion of the Tibet Plateau followed by the India-Eurasia collision. The Cenozoic tectonic activity of the Altyn Tagh fault is crucial to the process and mechanism of the uplift and expansion of the Tibet Plateau. In recent years, detailed studies have been made on the Altyn Tagh fault zone to acquire the characteristics of the strike-slip movement, strike-slip displacement, and strike-slip rate of this fault by means of thermochronology, fault geometry and kinematics, sedimentology, magnetostratigraphy, and seismology. There is also some research on the stratigraphic age and sedimentary evolution of Cenozoic sedimentary basins along the Altyn Tagh fault zone but most of these studies are limited to a single basin and there is a lack of comparative understanding of the overall basins along the Altyn fault zone, which probably lead to various understandings of the initiation age of strike-slip of the Altyn fault and the uplifting history of the Altyn Mountain. In this study, we summarize the research of magnetostratigraphy and sedimentology on the Cenozoic sedimentary basins along the Altyn Tagh fault zone in the past two decades and establish and chronological framework of the Cenozoic sedimentary sequence in these basins along the Altyn Tagh fault zone combined with thermochronology and other data. A three-stage evolution model of the Altyn Tagh fault zone is proposed in this article:the Altyn Tagh fault zone was dominated by a large-scale strike-slip movement, accompanied by the smaller-scale uplift of the Altyn Mountain during Eocene to the Middle Miocene; the Altyn Mountain began to uplift on a large scale, accompanied by a smaller-scale strike-slip movement since the Middle Miocene; the tectonic activity of the Altyn Tagh fault zone has been significantly strengthened since the Late Miocene.