Mesozoic–Cenozoic source provenance and thermal evolution of the southwestern Tien Shan, SE Uzbekistan

Abstract The evolution of intracontinental mountain ranges poses significant challenges in understanding Earth’s geological history. Among these mountain ranges, the Tien Shan in the Central Asia stands as one of the most important examples. Its crustal structure was shaped during the Paleozoic closure of the Paleo-Asian Ocean and has since undergone multiple reactivations driven by distant tectonic processes along the Eurasian plate margin, culminating in its modern morphology. While geochronological and thermochronological studies in the Tien Shan have largely focused on the range’s core, revealing a complex Mesozoic tectonic history with a dominant Cenozoic overprint from the India-Eurasia collision, the westernmost regions remain comparatively understudied. The aim of this study was to further provide constraints on Meso-Cenozoic source-to-sink dynamics and associated basin-mountain interactions, and Cenozoic reactivation and intracontinental deformation of the westernmost Tien Shan. Here we present new detrital zircon U-Pb data for the Early Jurassic to Neogene, and apatite fission track and (U-Th)/He data for the Early Jurassic and Cretaceous sedimentary rocks in the southern Gissar range (western Tajik basin), westernmost Tien Shan. Detrital zircons from the Jurassic to Neogene sandstone samples display various Precambrian single-grain ages and distinct Paleozoic age peaks (425–270 Ma), indicative of origins from the North and Middle Tien Shan. In contrast to the central-eastern Tajik basin, source-to-sink analyses reveal that the Pamir plateau has not been a main source area for the western Tajik basin. Apatite fission track and (U-Th)/He data, and associated thermal history modeling results, suggest that the Cenozoic inversion of the Tajik basin’s margin in response to the India-Asia convergence occurred as early as the early Oligocene, followed by another distinct exhumation phase since the mid-Miocene.