Recent Spatial and Temporal Changes in the Stress Regime along the Southern Tunisian Atlas Front and Gulf of Gabes: New Insights from Fault Kinematics Inversion
Mohamed Gharbi, Olivier Bellier, Amara Masrouhi, and Nicolas Espurt
The Southern Atlassic Front of Tunisia results from the convergence between Nubia and Eurasia. We present evidences for spatial and temporal changes in the stress state by inversion of geologically determined fault slip vectors. The inversions of fault kinematics data reveal distinct temporal changes in states of stress during the Miocene-Pliocene and Quaternary deposits. The paleostress (older) state is characterized by a regional compressional tectonic regime with a mean N131±09°E trending horizontal maximum stress axis (σ1). The modern (younger) state of stress also corresponds to compressional tectonic regime with a regionally mean N04±07°E trending horizontal σ1. Locally the modern stress states corresponds to a compressional tectonic regimes with NE trending σ1, due to stress deviations related to lithological/rheological inhomogeneities or to fault kinematics. The modern stress states, deduced from the youngest fault kinematics data, reveal the recent tectonic activity along the foreland of Atlassic structures and probably generate the newly thrusting structures. Eastward, Gulf of Gabes is maybe characterized by extensional structures at a crustal scale related to the N to NNW trending right-lateral transtensionnal margin. We propose that the spatial and temporal changes in the stress during the Miocene-Pliocene and Quaternary may result from two structural effects:  The migration of the convergent boundary between Nubia and Eurasia toward the south in the internal zone (i.e., Atlassic domain) attested by the tectonic inversion of the inherited structure and  the Mesozoic Ionian oceanic lithosphere in the Sicilian basin (Eastward of SAFT) which generated transtensional basin.
AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013