至今仍在活动的阿尔金左旋走滑断裂构成了青藏高原地质意义上的北界,是世界上规模最大、也是最重要的巨型断裂之一,其新生代的快速走滑是吸收印藏碰撞变形的重要途径.对其新生代大规模走滑的起始时间目前尚无一个统一认识,主要受其本身复杂性的限制,也很难找到一个确切的直接证据来限定其走滑时间.本文从阿尔金断裂走滑作用相关的一系列地质现象入手,从多个角度综合阐述这一科学问题,包括柴达木盆地西缘的物源变化、塔里木盆地东南缘走滑挤压挠曲盆地的形成、青藏高原北缘上地壳强烈的NE-SW向缩短变形、走滑相关盆地的形成以及与走滑断裂相伴生的线性隆起形成等等.结果表明与阿尔金断裂左旋走滑相关的地质现象大量出现在中中新世以后,约束得出阿尔金断裂新生代大规模的走滑始于约15±2Ma.此外还分析了本文结果所得出的阿尔金断裂新生代长期滑移速率与实测第四纪滑移速率相互矛盾的原因,并讨论了阿尔金断裂左旋走滑与阿尔金山的隆升以及青藏高原东北缘在中中新世的构造应力转换之间的关系.%The active left-lateral Altyn Tagh Fault (ATF) defines the tectonic northern edge of the Tibetan Plateau,and is one of the largest and most important faults worldwide.The fast slip along the fault is regarded as one of the major ways to absorb the IndiaTibet convergence.However,when did Cenozoic left-slip on the ATF initiate remains a subject of hot debate possibly due to the complexity of the fault itself.In this paper,we focus on the various geological responses to the left-slip on the fault,and figure out their formation time which is helpful in understanding the timing of left-slip along the ATF.They are:(1) provenance change in western Qaidam Basin; (2) Late Cenozoic flexural SE Tarim Basin; (3) NE-SW directed upper-crustal shortening in NE Tibetan Plateau; (4)strike-slip related basins and (5) the linear mountain along the ATF.The result shows that these slip-related phenomena all formed after Mid-Miocene (ca.15 ±2Ma),which we accordingly interpret as the initial time of left-slip along the ATF.We also analyze the possible reason for the discrepancy between Cenozoic long-term slip rates and reported Quaternary slip rates along the ATF,and discuss the ways how the activities of the ATF formed the Ahyn Mountain and controlled the Mid-Miocene tectonic reorganization in NE Tibetan Plateau.
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