Salt Tectonics During Lithospheric-Scale Rift and Basin Inversion Stages: Insights from High-Resolution Numerical Modeling

The influence of evaporites on the tectonic style of rift basins, as well as subsequent basin inversion and fold-and-thrust belt evolution, has gained increasing attention from both the scientific community and industry. Salt deposits play a crucial role in hydrogen and CO₂ storage and are associated with geohazards such as landslides. Despite this, the impact of pre-rift décollement layers on the subsidence, thermal evolution, fault spacing, rift linkage, and erosion-deposition patterns throughout the Wilson cycle remains insufficiently explored.

This study employs high-resolution (300–400 m), lithospheric-scale 3D thermo-mechanical models using I3ELVIS to simulate the successive stages of rifting and subsequent contraction. The models incorporate simplified erosion and sedimentation processes through diffusion, with a specific focus on the role of pre-rift evaporitic décollement layers. An low-viscosity evaporitic layer is defined at the base of the pre-rift sedimentary sequence, and the effects of varying evaporite thickness, density, and erosion-sedimentation rates are systematically analyzed. Plate divergence, simulating a 2 cm/yr lithospheric extension rate, transitions to a 1 cm/yr convergence rate to model basin inversion. Extension-to-contraction transitions are implemented after varying degrees of extension, either during continental rifting or following crustal break-up.

The rift basins in the models exhibit diverse salt tectonic structures, including salt diapirs, minibasins, and rollover structures. Additionally, localized contractional structures form along the tilted flanks of half-graben depocenters. Basin inversion reactivates salt structures along inherited basin margins, promoting the development of diapirs above the rising orogenic core. Thin-skinned thrust sequences are efficiently decoupled from basement-involved structures by the inherited evaporitic décollement layer. Although the models are not site-specific, the results align with observations from rifted (passive) margins and regions such as the Atlas and Carpathians Mountains.