Abstract
This chapter provides an overview of data-compilation, recently published, as well as newly collected data on the structure and evolution of Southern Atlas front in Tunisia. The Northern Chotts Range, one of most geologic features in southern Atlas, separates a dominantly deformed area of Gafsa to the north, from a relatively undeformed area of Chotts basin and Saharan platform to the south. The Cenozoic contractional period shapes a chain with mixed thick- and thin-skinned tectonic style, controlled by deep-seated basement faults with shallower decollement within the sedimentary cover. The present-day general "en echelon" fold distribution of the overall Northern Chotts Range, the age and the geometry of units, are likely the surface expression of the "en echelon" WNW- to- NW-trending faulting, which controls the fold's emplacement and style. These systems usually exhibit a fault kinematics, with striation showing a multiphase history. During Mesozoic times, the extensional activity of WNW- to- NW-trending normal faults is associated with significant thickness and/or facies variations comprising abundant syntectonic sequences. The growth of major synsedimentary typical normal fault systems, which produce a general framework delivering tilted blocks basin geometry, displays well-developed half-graben fill and large rollover structures along the southern Atlas. The Northern Chotts Range is, therefore, considered as the results of the Mesozoic inherited faults reverse-reactivation. The Chotts basin was previously considered as a large anticline related to the Cenozoic compressional events to explain the gentle deep observed "antiform structure". It was, therefore, marked as the far-foreland of the southern Tunisian Atlas. Like many other inverted margin, extensional inherited structures are still preserved in the southern Tunisian Atlas. The Chotts preserves Mesozoic extensional structures, of which the so-called Chotts anticline is defined in this study as large inherited rollover structure. The subsequent tertiary compressional front will be, therefore, repositioned in the Northern Chotts Range Front.