International audience; The breakup of Eastern Gondwana started during the Early Jurassic with the separation of Antarctica and Madagascar from Africa. While margins architecture has been described along the Western Somalia Basin and the central Mozambique, the spatial extent of rifting further south – i.e. the Natal Valley – remains poorly documented. Seismic reflection profiles interpretation, 40Ar/39Ar ages and isotopic data show the existence of a plume related magma-rich margin – the Natal segment – characterized by a large volume of seaward dipping reflectors inferred to be basalts. In particular, the contrast in lithosphere rheology, probably caused by a Meso-Neoproterozoic belt between the Kaapval and Grunehogna Archean cratons, favored extension and upwelling from a deep mantle thermomechanical anomaly, the so-called Karoo superplume that started at around 180 Ma. Further, the presence of stretched continental crust at around 30°S implies a more southerly position of Antarctica which will need to be considered in future kinematic models.