Structural Inversion of Rotational and Oblique Rifts: Inferences from 3D Coupled Thermo-Mechanical and Surface Processes Models

Continental extension is often oblique, resulting in rotational rifts with characteristic V-shaped basins, oblique transtensional structures and along-strike variations in the overall lithospheric structures. Inherited crustal or mantle fabrics exert a first-order control on the structural style of extension and subsequent basin inversion, and lead to different uplift-subsidence rates in the modeled basins and orogens.

In this study, we conducted a series of 3D numerical experiments to simulate the successive stages of rotational and oblique rifting and subsequent basin inversion in order to understand the resulting strain partitioning and lateral variations, while simultaneously tackling the coupling between tectonics, mantle melting and the surface processes. To obtain this, we applied the coupled I3ELVIS-FDSPM numerical code (Gerya 2015, Munch et al. 2022), which is based on staggered finite differences and marker-in-cell techniques, and solves the mass, momentum and energy conservation equations for incompressible media. The model also takes into account simplified melting processes and erosion-sedimentation by diffusion.

The modeling results are compared to observation data from several Mediterranean back-arc basins. In the Tyrrhenian, Pannonian and Alboran Basins, temporal variations of different plate convergence rates, slab retreat velocities and rotational plate movements lead to rotational/oblique extensional basin formation, which recently changed to structural inversion. In fossil rifts, such as the Pyrenees and Great Caucasus, the inversion has already reached the mature orogeny phase, where high strain-rate convergence has ultimately overprinted the former basin structure.

The study was supported by the 134873 OTKA research fund.