Constraints of basement geometry and supra-salt cohesion on deformation of salt-bearing fold-and-thrust belts: a discrete-element study
Résumé
Salt-bearing fold-and-thrust belts (FTBs) in foreland basins exhibit complex structural architectures, primarily governed by the interplay among basement geometry, supra-salt mechanical strength, and the detachment behavior of intervening salt layers. However, the respective roles of basement surface geometry and supra-salt cohesion in controlling deformation localization, thrust segmentation, and fold development remain poorly constrained, particularly in regions with limited subsalt seismic imaging. To address this gap, we conducted two-dimensional discrete element method (DEM) simulations to systematically assess how variations in basement surface geometry and supra-salt cohesion influence the structural evolution of salt-bearing FTBs. The results show that lateral variations in basement morphology produce significant heterogeneity in salt layer thickness, thereby strongly influencing salt particle rearrangement and deformation localization. Redistribution of salt particles from thick to thin zones leads to compression and uplift in the overburden, while reverse movement induces extension and subsidence. A relatively low supra-salt cohesion promotes more rapid deformation front propagation, increased fold density, and more frequent salt piercement, whereas a relatively high cohesion delays deformation front propagation and favors fewer but higher-amplitude folds and enhanced thrust faulting. Comparisons with representative natural examples demonstrate that the models broadly capture the main structural features of salt-related FTBs at a regional scale, including large-scale thrust systems and salt-cored folds. Overall, our findings highlight that basement relief and supra-salt cohesion are first-order controls on structural evolution in compressional salt-bearing systems, thereby enhancing the understanding of deformation localization, thrust segmentation, and fold development.
