Role of synsedimentary strike-slip faults in the formation of Moroccan Triassic basins

A structural transect through the High and Middle Atlas of Morocco

“…Pre-Mesozoic basement rocks affected by the Hercynian orogeny crop out in antiformal culminations within the High and Middle Atlas, and more extensively in the Moroccan Meseta, west of the Middle Atlas, and in the Anti-Atlas, south of the High Atlas. Mesozoic sedimentation in the Atlas domain was initiated within Triassic rift basins whose NE-SW structural trend was inherited from Hercynian structures (Laville and Petit, 1984;Froitzheim et al, 1988;Laville et al, 1995), and that were filled with detritic red beds and tholeiitic basalts. Lower Lias platform limestones and dolomites sealed the Triassic rifts (Laville et al, 1995).…”

Characterization of the Cretaceous aquifer structure of the Meskala region of the Essaouira Basin, Morocco

“…Details are found in Medina and Chrowicz (1983), Souid (1983), Laville and Petit (1984), Medina (1984Medina ( , 1985Medina ( , 1989, Broughton and Trepanier (1993), Laville (1993, 1995), Le Roy et al (1997) and Piqué et al (1998). In the Essaouira Basin, the major NW-SE early extension in the Triassic formed a series of grabens resulting from reactivation of Hercynian age faults trending NNE, NE and E. Early Mesozoic sedimentary sequences demonstrate thickening and facies changes in the direction of fault planes (Tajeddine, 1991), and to a lesser extent in the late Mesozoic (Ettachefini, 1992).…”

“…In brief, the stratigraphy and structure of the Essaouira Basin are primarily due to two major tectonic periods and penecontemporaneous and intervening sedimentation cycles. The first was the extension of the central Atlantic during the Triassic to lower Cretaceous period which created the sedimentary basin, and the second was the syn to post-Cretaceous compression linked to the collision between Africa and Eurasia which is responsible for the formation of the Atlas Mountain chain (Medina and Chrowicz, 1983;Souid, 1983;Laville and Petit, 1984;Medina, 1984Medina, , 1985Medina, , 1989Broughton and Trepanier, 1993;Laville, 1993, 1995;Le Roy et al, 1997;Piqué et al, 1998). These two contrasting tectonic episodes lead to the definition of four sedimentary deposit cycles; Permian-Triassic, Jurassic, Cretaceous, and Tertiary (Table 1) (Duffaud, 1960;Choubert and Faure-Muret, 1962;Ambroggi, 1963;Duffaud et al, 1966;Adams, 1979;Wiedman et al, 1982).…”

Sedimentary dynamics and palaeotectonic structuring during the Toarcian–Aalenian in the southwestern Middle Atlas (Morocco)

“…While the role of transverse NW-SE palaeo-faults is well established both in the eastern Middle Atlas (Ichou-Anou accident; Benshili (1989)) and in the High Atlas (Demnat accident; Marrec and Jenny (1980)), the dominant transverse structure in the southwestern Middle Atlas is NNE-SSW. This orientation corresponds to reactivated late Hercynian accidents, which are well defined in the Moroccan Atlas (Mattauer et al, 1977;Laville and Petit, 1984), in the western Middle Atlas and in the Palaeozoic basement inliers of the Central Plateau (Allary et al, 1972), where the "dextral shear zone" of the western meseta oriented SSW-NNE (Laville and Piqué, 1991) separates the coastal meseta from the Central Plateau. In the study area, the southwestern termination of the Middle Atlasic trough, which is controlled by a complex structural framework inherited from Hercynian events, raises the question of the distinction between Tethyan and Atlantic paleogeography and structural influences.…”