Late Cenozoic Pamir-Tianshan convergence and its tectonic-climatic implications revealed by low-temperature thermochronology

The Cenozoic India-Eurasia collision drove widespread intracontinental deformation across Central Asia, culminating in northward indentation of the Pamir and its eventual contact with the South Tianshan. However, the timing and kinematic development of the Pamir-Tianshan convergence, as well as its influence on shaping regional topography and climate, remain debated. Here we report more than 200 new apatite (U-Th-Sm)/He (AHe), apatite fission-track (AFT), and zircon (U-Th-Sm)/He (ZHe) dates from 49 samples collected from the North Pamir-South Tianshan convergence zone in the westernmost Tarim Basin, NW China. These data, integrated with inverse thermal history modeling and probabilistic estimates of cooling onset, reveal a protracted, stepwise convergence history since the late Eocene. Initial convergence occurred from the late Eocene to the middle Miocene (~35-15 Ma), marking the onset of cooling and deformation in the hinterlands. During the middle Miocene (~15-10 Ma), deformation propagated basinward into the foreland, accompanied by the activation of frontal thrust systems in both orogens. Continued convergence during the late Miocene (~10-5 Ma) led to initial interaction between the North Pamir and South Tianshan thrust systems, followed by propagation of deformation along frontal thrusts during the Pliocene to Quaternary (~5-0 Ma), producing the present-day superimposed and imbricated thrust architecture in the convergence zone. This progressive convergence and surface uplift gradually narrowed and closed topographic corridors between the Pamir and Tianshan, restricting westerly moisture transport into the Tarim Basin and promoting the development of the Taklimakan Desert. Together with existing paleoclimate records, our results demonstrate that regional tectonic processes, acting in concert with global climatic forcing, played a dominant role in the long-term aridification of Central Asia.