Is the Mejerda Wedge-Top Basin of Northern Tunisia a Consequence of Basal Friction Change? a Theoretical and Experimental Approach

Abstract

In Northern Tunisia, the extensional Mejerda basin is developed over a major compressional boundary between the Tell fold-thrust belt to the north and the Atlas intra-continental system to the south. The abundance of Triassic salt structures in northern Atlas and under the Mejerda basin suggests a lateral change of the friction along the basal detachment. Such abrupt transition plays a significant role in the structural styles of the studied region and especially in the Mejerda basin. Therefore, we have developed prototypes with a basal frictional transition to study, through numerical and physical simulations, wedge deformation style. Accordingly, the one step results of all run numerical tests depict normal faults localized at this basal transition. In addition, the physical models in sandbox allow us to verify the mechanical results and to observe more deformation steps, in 2D and in 3D views. As a result, we observed via the sandbox experiments extensional features such as grabens. Finally, we highlight that compression can lead to build an extensional basin at the top of a thrust wedge as expression of basal friction change and we interpret the Mejerda basin accordingly.