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Active shortening structures in Northern Tunisia have developed by tectonic inversion since the Pliocene, after Late Miocene extensional collapse of the whole region. Restored Plio-Quaternary deformation observed on reflection seismic lines indicates deformation rates around 0.6–0.8 mm/yr in the studied segments and larger amounts of shortening to the West of Northern Tunisia (16%) than to the East (7%), which suggests tectonic inversion started earlier to the West and later propagated eastwards, reaching Northeastern Tunisia in the Late Pliocene. This shortening is registered on striated pebbles in Quaternary alluvial terraces and fault-slip data giving two populations of strain ellipsoids with N–S and WNW-ESE maximum shortening. Morphometric analysis in combination with field fault segmentation mapping show that topographic uplift and drainage rejuvenation occurs in relation to 20–30 km long ENE-WSW reverse fault segments and related antiforms that are offset and linked by E-W to WNW-ESE dextral and NE-SW-oriented sinistral faults. The largest fully linked fault system is the Alia-Thibar fault. This 130 km long fault zone shows an helicoidal geometry with five different fault segments, including reverse, dextral, sinistral and oblique faults. Due to the young age of tectonic inversion, after late Miocene extensional collapse of the region, the present relief of Northern Tunisia is characteristic of a young thrust and fold belt, with dominating axial valleys along synforms and an incipient transverse drainage development propagating from West to East.

The Cap des Trois Fourches (Eastern Rif, northern Morocco) metamorphic basement exposes two major tectonic units, namely the Taïdant unit underthrusting the overlying Tarjât tectonic unit. The Tarjât tectonic unit is composed of metamorphic rock originating from detrital material. This upper Tarjât tectonic unit exhibits: (1) orthogneiss bodies being Paleozoic in age and (2) evidences showing a retromorphose during the Alpine orogenesis. U-Pb SHRIMP zircon geochronology from the orthogneiss bodies has yielded Sakmarian (early Permian) ages for the intrusion of their protoliths. The lower Taïdant unit is formed of green and brown shales associated with quartzite beds. A Mesozoic age is commonly accepted for this unit. The internal structure of the Tarjât tectonic unit consists in km-scale folds trending ENE-WSW with an up-dip direction towards the SE. This compressional deformational stage was superimposed on internal thrust sheets controlled by ductile shear zones with a SW-vergent transport sense. The lower Taïdant unit shows conspicuous bedding associated with a penetrative foliation outlining a monocline structure dipping gently towards the NW. The major ductile-brittle detachment fault bounding the upper Tarjât tectonic unit from the lower Taïdant unit –i.e. the local basement– exhibits evidences for a top-to-the-west sense of motion. We assume that this specific fault is the prolongation into the Cap des Trois Fourches area of the extensional detachment previously described in the Temsamane area. Therefore, this low angle detachment fault is a major tectonic element extending hundreds of km through the Eastern Rif. We postulate that this major detachment roots deep in the Eastern Rif basement. This detachment is cut at the surface by the Nekor normal-sinistral strike-slip fault that separates thin 24–32 km thick metamorphic Eastern Rif crust from the 50–55 km thick crust of the Western Rif. This transtensive fault system exhumes the Rif middle crust, represente