Influence of the Paleo-Uplift Amplitude on Structural Deformation in the Salt-Bearing Fold-and-Thrust Belt: Insights from Analogue Modeling

Paleo-uplift is one of the main controlling factors for the structural deformation of the salt-bearing fold-and-thrust belt (FTB). It is common that the amplitude of paleo-uplift is variable in spatial distribution, which may lead to more complex deformation in the salt-bearing FTB. In this context, we designed four groups of experimental models with two décollement layers to investigate the influence of the paleo-uplift amplitude on the deformation mechanism in the salt-bearing FTB. Results indicate that the paleo-uplift amplitude has a significant influence on the deformation kinematics and the development of salt structure. With respect to the deformation kinematics, our study reveals that the presence of paleo-uplift has no significant influence on propagation along the basal décollement, but dominates the development of shallow deformation fronts. Compared with lower amplitude paleo-uplift, the higher amplitude paleo-uplift provides a pinch-out boundary for the upper décollement, leading to the faster propagation of the deformation along the shallow décollement. Regarding the development of salt structure, the experimental results indicate that the influence of paleo-uplift on salt rock flow increases as a function of the paleo-uplift amplitude, which leads to the low wedge taper and the thickening of the overlying strata on the top of paleo-uplift. With the increase of paleo-uplift amplitude, the salt structure of salt weld migrates from the hinterland to the back edge of paleo-uplift. Our analogue modeling results shed lights on the formation mechanism of Kuqa FTB. The paleo-uplift in the Kuqa FTB dominates the development position of salt-related anticlines, and a high amplitude paleo-uplift is more advantageous for the development of complex structural deformation during forward propagation.