The effect of paleo-uplift on deformation mechanism in the Wupoer fold-and-thrust belt, NE Pamir: constraints from analogue modeling

Abstract:

Six analogue models were systematically run on real geological conditions to evaluate whether the Wulagen paleo-uplift controlled the deformation in the Wupoer fold-and-thrust belt, NE Pamir. Our analogue results demonstrate that in a fold-and-thrust belt where paleo-uplift is covered by a ductile décollement such as a gypsum layer, the paleo-topography of paleo-uplift plays an important role in the deformation mechanism. The results indicate that the front thrust fault slides along the ductile décollement and thrusts upwards preferentially to the surface in the foreland area where the paleo-uplift exits, forming a piggyback basin in the hanging wall. The results also suggest that the distribution range of the paleo-uplift is an influential factor in the formation of an arc-shaped fold-and-thrust belt. The laterally inhomogenous distribution of the paleo-uplift in the foreland area indicates that, the front thrust fault would be initially thrust to the surface on the same side as paleo-uplift occurrence and then gradually propagate towards the side without paleo-uplift occurrence, resulting in an arc-shaped distribution of a fold-and-thrust belt. This kinematic process is the cause of the vertical displacement of the front thrust fault in the area with paleo-uplift occurrence was much greater compared with the area where paleo-uplift was absent. Based on the analysis of experimental results, we suspect that the deformation of the Wupoer fold-and-thrust belt is largely controlled by the Wulagen paleo-uplift located in the NW of the thrust belt. Our finding suggest that the front thrust fault of the belt, the Pamir Front Thrust (PFT), developed preferentially in the western area with the Wulagen paleo-uplift and then propagated towards the east, forming an arc-shaped fold-and-thrust belt. The vertical displacement of the western part of the PFT was larger than that of the eastern part, resulting in the western part being thrust to the surface, while the eastern part became concealed underground.