Geodynamic evolution of the Tunisian margin during the Albian–Cenomanian: structural evidence of the Austrian orogenic phase and the early tectonic inversion of the Tunisian Atlas

The Zebbag and Fahdene formations outcrop onshore Tunisia and provide an excellent opportunity to test models of the tectonosedimentary evolution of this region during the Albian–Cenomanian. A NW–SE compressive stress regime resulted in shortening of the Tunisian margin and this compressional tectonism defines the Austrian phase described in the surrounding margins. This event is not widely documented, but regionally extensive tectonism is suggested by NE–SW thrusting and folding, which produced an angular unconformity, active halokinetic diapirs and transpressional NW–SE pull-apart basins. The observed compressional deformation can be considered as a precursor to the Alpine Orogeny and led to the inversion of palaeoblocks inherited from Tethyan Jurassic and Lower Cretaceous rifting. A late Albian–Cenomanian onset of compressional deformation along the Tunisian margin may be intimately related to the drift of Africa with respect to Europe and to opening of the Atlantic Ocean.

GPS Constraints on the Active Deformation in Tunisia: Implications on the Geodynamics of the Western Mediterranean

<p>The plate boundary in the western Mediterranean includes the Tunisian Atlas Mountains. We study the active deformation of this area using GPS data collected from 2014 to 2018. WNW to NNW trending velocities express the crustal motion and geodetic strain field from the Sahara platform to the Tell Atlas, consistent with the African plate convergence. To the south, the velocities indicate a nearly WNW-ESE trending right-lateral motion of the Sahara fault-related fold belt with respect to the Sahara Platform. Further north and northeast, the significant decrease in velocities between the Eastern Platform and Central – Tell Atlas marks the NNW trending shortening deformation associated with local ENE – WSW extension visible in the Quaternary grabens. The velocity field and strain distribution associated with the active E-W trending right-lateral faulting and NE-SW fault-related folds sustain the existence of three main tectonic blocks and related transpression tectonics. The velocity field and pattern of active deformation in Tunisia document the oblique plate convergence of Africa towards Eurasia. </p>