Numerical modelling of the Wilson Cycle: effects of orogenic inheritance on the formation of rifted continental margins

The Wilson Cycle describes the repeated opening and closure of oceanic basins from continental rifting to continent-continent collision. The correlation between ancient orogenic belts and young rift systems highlights the significance of orogenic inheritance in shaping the complexities of rifted margins. Orogenic belts can be classified as either pure shear double-vergent or simple shear single-vergent orogens based on their rheological properties and lithospheric deformation mechanisms during lithospheric shortening. Therefore, their resulting pre-rift conditions differ significantly by providing varying inherited structure. The actual inversion from orogen to rift remains poorly understood. For instance, how does inheritance from orogenic processes affect the evolution and final architecture of rifted margins?To investigate this, a numerical forward model was applied that integrates geodynamic thermo-mechanical and landscape evolution software. The simulations include continental collision, post-orogenic collapse and continental rifting, and breakup, through velocity boundary conditions that vary from compression to extension over time. The two end-member orogens are generated by the adjustment of crustal rheology and erosion efficiency. For comparative analysis, we also simulate the extension of laterally homogeneous lithosphere without orogenic inheritance.Results show that collision in cold and strong continental crust generally produces single-vergent orogens. The double-vergent orogen is formed in weak and hot continental crust with low erosional efficiency. However, a transition in the orogenic dynamics occurs under high erosional efficiency, leading to the development of single-vergent orogens for weak and hot crust. The double-vergent orogen features a wide zone of shortening (~350 km) with a large number of conjugate thrust faults. These faults all tend to reactivate as normal-faults during the subsequent phase of rifting and breakup generally occurs around an inherited, overthickened crustal root. These orogens produce largely symmetric rifts. In contrast, the single-vergent orogen is asymmetric with most shortening accommodated along one dominant interface during the orogenic stage. During rifting, this subduction interface is fully reactivated, accommodating most of the extension and determining the crustal breakup location. These orogens produce an asymmetric rift. In conclusion, orogenic inheritance controls the localization of deformation along pre-existing structural weaknesses and reactivation mechanisms, resulting in complex rifted margins.