Late Miocene-Quaternary thrusting in the Utique-Kechabta foreland basin of the Tell, Northern Tunisia

Abstract

Northern Tunisia is characterized by a complex orogenic system, the Tell fold-and-thrust belt (FATB), part of the Maghrebides, associated, to the South, to the Atlas FATB intra-continental chain. The South Tellian Front (STF) separating the two FATBs is bounded by Upper Miocene to Quaternary of the Mejerda wedge-top basin to the South-West and Utique-Kechabta basin to the North-East. The first one corresponds to an extensional basin developed during the Late Miocene to Quaternary compressions. On the other hand, field mapping and seismic profiles interpretations indicate that the Utique-Kechabta is characterized by tectonic accretion, thrusting of the Tell onto its foreland basin. In Bizerte Area (to the North of Utique-Kechabta basin), the subsurface structures underneath the Tell are characterized by pop-up/pop-down structures and important horizontal displacement. These Tellian structures are transported toward the SE over the major decollement level which corresponds to the Triassic salt and bounded southeastwards by the South Tellian Front. The latter, separating the Tell, propagates through Utique-Kechabta basin within the Upper Miocene series and cutting through apical parts of Triassic diapiric structures with transported salt plugs. The drastic change of the structural style from the Mejerda to the Utique-Kechabta basins can be partly controlled by the evaporites differential repartition, from Tell to Atlas. A tentative facies distribution map of the Late Triassic is presented, and it shows an evaporitic dominant facies in onshore Tunisia and along its coast, except in and Gulf of Tunis characterized by carbonate facies. These carbonates are analog of the dolostones of Southern Sicily known as good source rock and then offer an interesting potential to the Petroleum exploration in North Tunisia.