Analogue modelling of basin inversion: the role of oblique kinematics and implications for the Araripe Basin (Brazil)

Basin inversion is a process that takes place when a sedimentary basin is subjected to compressional stresses and may result in the reactivation of pre-existing faults and/or the localization of deformation along new reverse faults. The Araripe Basin (NE Brazil) is an example of a Cretaceous intracontinental aborted rift with its sedimentary infill found at ca. 1000 m altitude in the present day. Post-rift basin inversion is proposed as the cause of this topographic high, however how inversion mechanisms affected this basin is a matter of debate with two end member scenarios: reactivation of pre-existing normal faults leading to local uplift, or regional tectonic uplift. In this study, we conducted analogue models of basin inversion to test these scenarios. We present two series of crustal-scale brittle-viscous experiments: i) extension followed by compression without sedimentation, with a variation of rifting and inversion directions (orthogonal or 45° oblique) and ii) extension and compression with syn-rift sedimentation, with the same variation in rifting and inversion directions. We used a seed representing a structural weakness that was applied at the base of the brittle layer to localize deformation along the model axis. We found that orthogonal rifting without sedimentation forms through-going border faults, whereas oblique rifting creates initial en-echelon faults that eventually link up creating large border faults. Rift basins with syn-rift sedimentation evolved in a similar fashion, however sedimentary loading increased subsidence. During inversion, most deformation is accommodated along new low angle reverse faults. Within that framework, significant intra-graben fault reactivation occurred in models without sedimentation. By contrast, syn-rift sedimentation caused only minor reactivation of rift faults in oblique inversion since the sediments acted as a buffer during compression; no rift fault reactivation occurred in orthogonal compression situations. Comparing the existing scenarios for inversion in the Araripe Basin with our model results and field data show that these scenarios do not fully explain the natural example. Therefore, we propose an alternative scenario based on our models, involving oblique compression and the development of low angle reverse faults, which better explains inversion in the Araripe Basin.