Gravity contribution to the Mejerda foreland basin, Northwestern region of Tunisia

Abstract

The Mejerda basin in northwestern Tunisia is located between the Tell and Atlas Mountains and contains structures related to the complicated tectonic history of the study region. The Mejerda contains compressional structures related to the Cenozoic collision between Europe and Africa, and strike-slip faults related to extensional tectonics. As a result of the varied tectonic history, there has been numerous models of the basin formation ranging from simple grabens, pull-apart basins and foreland basins. In order to constrain the subsurface structure of the basin, a gravity analysis consisting of the construction of residual gravity anomaly maps, estimated depths from upward continuation and Euler deconvolution, and detailed two-dimensional forward models. The gravity analysis was constrained by a seismic reflection profile and a deep well. The map analysis indicated two separate basins, one called the Quaternary basin and another called the Pliocene basin. Based on the gravity depth analyses and the gravity forward modeling, and the residual gravity anomaly map, these basins were between 2.5 and 3 km thick, and separated by gravity maxima probably due to uplift of Triassic and Cretaceous sediments related to compressional tectonics and evaporitic movement. The Euler deconvolution analysis imaged a number of lineaments, interpreted to be faults, that trend in the NE and NW directions and these faults basically delineate the basins. Results confirm that the Mejerda basin is a wedge-top basin located in the foreland side of the Tellian thrust belt and consists of two separate basins whose origin was mostly determined by thin-skin compressional tectonics.