Tectonic processes of the Cenozoic Altyn Tagh Fault and its coupling with the Qaidam Basin,NW China

The active Altyn Tagh Fault in northern Tibetan Plateau is one of the largest and most significant linear structures in the world,and its Cenozoic activity is the important constraint on the growth mechanism of the Tibetan Plateau. In this paper,we illustrate that the Altyn Tagh Fault was dominated by basal shear during Late Eocene-Middle Miocene but by large-scale left-slip movement since then based on comprehensive analysis on uplifts of different trending in the Altyn Mountain and reported materials. We study systematically on the distribution,geometry and timing of the EW-and NW-trending fault systems inside the Qaidam Basin,and find that they are completely different fault systems forming in different time,different areas and controlled by different factors,showing a perfect coupling with the two-stage movement of the Cenozoic Altyn Tagh Fault. We also discover that height and width of the Altyn Mountain culminated in Mid-Miocene and then decreased according to the sedimentary and structural characteristics in NW Qaidam Basin,which can be well explained by the transition from basal shear to left-slip of the Altyn Tagh Fault.