Structural analysis of the central Tunisian Atlas: Implications for salt-related structures and conjugate strike-slip faults

Abstract

This scientific study aims to investigate the geological characteristics and tectonic processes of the central Tunisian Atlas region, focusing on the influence of tectonic events related to the Jurassic-Early Cretaceous Tethyan rifting and the subsequent Cenozoic tectonic inversion and uplift. In particular, this research emphasizes the strong control of tectono-sedimentary events on the geology of the central Tunisian Atlas, with specific attention given to the understudied isolated salt-related structures. To gain insights into the relationship between deep-seated faults, salt tectonism, and the conjugate strikes-slip faults, this study is based on subsurface data, including 2D seismic reflection and gravity data. The analysis investigates, the location of salt extrusions in relation to fault intersections. Results derived from subsurface data indicate that diapiric intrusions primarily occur at the junctions of major fault systems likely inherited from the Triassic-Jurassic Tethyan period. Notably, salt migration was remarkably active during the early Cretaceous, as evidenced by halotectonic sequences and salt-related mini-basins. Furthermore, fault blocks display sedimentary infill above tilted blocks, where salt structures appear to occur at their peripheries. During the subsequent tertiary compressions, the structural configurations of the basin (i.e., Z-shape basin) promote the strike-slip movement along pre-existing faults. This new structural interpretation suggests a closely relationship between fault zones inherited from the Jurassic-Early Cretaceous Tethyan Opening and isolated salt-related structures. The subsequent Cenozoic shortening events, including the Atlassic and Alpine events, have led to uplift of the deep-seated faults, facilitating the ascension and deformation of Triassic evaporitic sediments within subcircular isolated structures. Field observations and seismic sections indicate the presence of sedimentary gaps resulting from these processes. The findings of this study contribute to a comprehensive understanding of the deep tectonic framework and shallow salt-related structures in the central Tunisian Atlas.