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Palaeo-uplifts often exist in fold-and-thrust belts. However, their effects on the deformational process have not yet been well understood. To evaluate such effects, six analogue models were systematically run based on geological features of the Wupoer fold-and-thrust belt (FTB), NE Pamir, where the Wulagen palaeo-uplift with overlying gypsum bed has been clearly identified. Our analogue results demonstrated that the palaeo-uplift (its location and inhomogenous distribution), accompanied with overlying gypsum bed that serves as ductile décollement, plays a critical role in localizing the front thrust fault and shaping it into arc form. The results indicate that the front thrust fault slides along the ductile décollement (gypsum bed), and breaks through onto the surface at the region where the palaeo-uplift develops, forming a piggy-back basin in the hanging wall. It suggests that the palaeo-uplift with consequent topographic variation of the overlying ductile décollement localizes the breakthrough point of the front thrust fault. In addition, the results indicate that the front thrust fault (Pamir Front Thrust, PFT) initially broke through in the location where it develops the Wulagen palaeo-uplift and propagated aside. This resulted in the distance between the PFT and the basement-involved fault (Main Pamir Thrust, MPT) to decrease from the region with palaeo-uplift to the areas aside without palaeo-uplift, thereby forming the arc-shaped PFT in map view. The results of this study also provide a revised geological model, which emphasizes the effect of décollement layer on absorbing the slip along the PFT. Our results provide a new mechanical interpretation of the deformation of Wupoer FTB, NE Pamir. [ABSTRACT FROM AUTHOR]

The tectonic evolution of the Pamir bears essential information for understanding intracontinental tectonic processes within the context of India-Asia convergence. However, it is unclear whether the arcuate shape of the Pamir is entirely the result of the India-Asia collision, or may have been in part an inherited, pre-Cenozoic feature. In this study, we address the evolution of the NE Chinese Pamir during the Paleogene by reviewing the stratigraphy of twelve sections in the western Tarim Basin and the establishment of sedimentary facies. The results indicate three episodes of deposition of alluvial coarse sediments in the foreland regions of NE Chinese Pamir during the (1) early Paleocene, (2) late Paleocene to early Eocene and (3) middle Eocene to Oligocene, respectively. These are correspondingly attributed to (1) retroarc deformation in an Andean-type margin of the southern Asia during subduction of the Neo-Tethys Ocean, (2) the immediate response in the Pamir to the India-Asia collision, and (3) continued India-Asia convergence. The alluvial conglomerates with grain-size up to 5–10 cm, imply a transport distance <60 km from the fan apex. This result, together with the 20–50 km northward thrust displacements, suggests that the orogen/basin boundary between the Pamir and the Tarim-Alai Basin was located less than ca. 80–110 km to the south from the present location of the Main Pamir Thrust during the Paleogene, indicating the arcuate shape of the Pamir was already largely established by the Paleogene, rather than entirely a result of the India-Asia continental collision. [ABSTRACT FROM AUTHOR]