Syn-Collision Folding and Multi-Layers Detachment in the Molassic Basin, Northeastern Tunisia

Abstract

Tunisia had been the place of various tectonic episodes which have drawn the actual structural map of the country. The Neogene period was the most active period in which the collision contributed to the mountain ranges formation such as the Atlassic chain. The contrast of mechanical behavior between the different sedimentary units of the cover and the substratum is a determining factor that has controlled the deformation style of many folding structures. Detachment folding has been studied on the basis of field and seismic data examples from the Northeastern Tunisia. We discuss different aspects of detachment to constrain the chronology of structural events and understand the cover‒substratum relationship during the major folding phases. In the present paper, we found that the deformation style admitted previously do not reflect adequately the tectonic structure of Kechabta Neogene basin (North of Tunisia). The cover-substratum relationship study at this area revealed two major shortening phases; the first had been happened during the Upper Tortonian and the second in the Lower Quaternary. The resulting folding style is characterized by disharmonic and multi-layers detachment phenomena produced by incompetent evaporitic sequences. The two described folding phases are superimposed and testify at a large scale the continental collision which controls the North African margin during the Late Miocene to the Quaternary.

Control of Hercynian Orogeny on basin evolution on the southern margin of the Tethyan region: A review and new insights

“…The Zagros collisional orogen records the initiation of the collision at 34 Ma with the final closure of the Neotethys at 20 Ma (Mouthereau et al, 2012). Several phases of basin inversion occurred in Tunisia (western North Africa) and the eastern Mediterranean (eastern North Africa) from the Late Cretaceous (Abd‐Allah et al, 2020; Bosworth & Durocher, 2017; Khomsi et al, 2009; Ramzi et al, 2020); however, in these regions, the Neotethys and Alpine Tethys Oceans did not thoroughly close and the basin inversions were relatively weak. Basin inversion seldom occurred during this period in the central region of North Africa from the Pelagian to Sirte seas; most of this region experienced extensional subsidence (Abadi et al, 2008; Abdunaser & McCaffrey, 2014; Hallett & Clark‐Lowes, 2017), and continues even today in some areas (Capitanio et al, 2011; Tugend et al, 2019), very different from the adjacent regions.…”