Search

The Keping fold-and-thrust belt (FTB) is located along the southern foreland of the Chinese Tian Shan, consisting of 3–6 rows of E - to NE-trending thrusts. Determining the time of thrusting and folding within the Keping FTB is crucial to understand the process and characteristic of tectonic deformation along the southern Tian Shan foreland. Here, we present new deformation ages of four thrusts within the Keping FTB by using the apatite (U Th)/He thermochronometer. Based on analyses of 59 single-grain apatite (U Th)/He ages of 13 sandstone samples collected from the hanging-walls of the four thrusts, the deformation ages of two thrusts located at the northern part of the western Keping FTB were constrained to be ~12 Ma and ~ 11 Ma, respectively; while those of two thrusts located at the southern part of the eastern Keping FTB were interpreted to be ~14 Ma and ~ 13 Ma, respectively. The above deformation ages, together with previous studies, suggest that the Cenozoic deformation across the southern Tian Shan foreland initiated at ~16–12 Ma, and the propagation process of the Keping thrust system is laterally non-synchronous. Additionally, the million-year-scale crustal shortening rates of the Keping FTB were recalculated to be ~2.2–3.9 mm/yr in its western segment and ~ 1.3–3.6 mm/yr in its eastern segment, based on the new age constraints of initial tectonic deformation and published shortening estimates. • The Cenozoic deformation within the Keping thrust belt initiated at ~16–12 Ma. • Propagation processes of the Keping thrust system are laterally diachronous. • Tectonic scale shortening rate of the Keping thrust belt is ~1.3–3.9 mm/yr. [ABSTRACT FROM AUTHOR]

The Tajik Basin, located at the west of the Pamir, is characterized by a series of thin-skinned folds and thrusts within its interior. Constraining the onset of deformation of these structures is important both for illustrating basin inversion process and for understanding growth history of the adjacent Pamir. To date, the timing of thrusting and folding within the Tajik Basin has not been well studied. In this study, we determined the timing of fault motion of the Aruntau thrust in the central Tajik Basin by using apatite (U Th)/He thermochronometry. Apatite (U Th)/He age data of sandstone samples collected from the hanging wall of the Aruntau thrust fault, combined with thermal history simulation, constrains the onset of rapid cooling of rock samples at ca. 10–6 Ma. Given the compressional tectonic regime, we propose that the observed rapid cooling was caused by thrust-induced exhumation, and thus, the cooling age of ~10–6 Ma approximately represents the timing of thrusting initiation. Integrated with previous studies, we found that the late Miocene tectonic deformation was not only circumscribed within the Tajik Basin, but also occurred in the areas north and east of the Pamir and within the Pamir. We suggest that the synchronously widespread tectonic deformation in the Pamir-Tian Shan convergence zone reflects the enhanced northward indentation and lateral growth of the Pamir since the late Miocene. • Thin-skinned shortening of the central Tajik Basin initiated at ~10–6 Ma • The late Miocene tectonic deformation is widespread around and within the Pamir. • The late Miocene deformation is related to the northward motion and growth of Pamir. [ABSTRACT FROM AUTHOR]