Chapter 26 - Salt Tectonics in the Atlas Mountains of Morocco

Abstract

The principal objective of this paper is to summarize the large data set gathered in the last few years on the Early-Middle Jurassic diapiric evolution in the well-exposed Central High Atlas in Morocco. Field data on both structural geology and sedimentology of halokinetic sequences, significant remote sensing mapping using good quality satellite images, thermal modeling and subsidence analysis, balanced and restored cross sections, and analog modeling allowed us to construct an integrated tectono-sedimentary interpretation of a salt-related rift basin. Three characteristic regions are summarized here to show the tectonic and diapiric evolution of the study region: Tazoult, Azourki, and Imilchil. Salt ridges (Tazoult, Jbel Azourki, and Tassent salt walls) above blind basement faults developed a polygonal array bounding thick synclines (minibasins) with different orientations. The Imilchil minibasins show diachronous age of their infill, which is a typical characteristic of diapiric regions. The Tazoult and Jbel Azourki salt walls developed an allochthonous salt body starting during the Late Pliensbachian-Aalenian time. Although only Lower and Middle Jurassic halokinetic sedimentary sequences are preserved in most of the Central High Atlas, younger synclines (minibasins) along the northern boundary of the Atlas (Demnate region) show development of Late Jurassic and Early Cretaceous minibasins. At the larger scale, the diachronous evolution of the extension and diapirism along the Atlas Basin suggests that diapirism and salt withdrawal play an important role during the development of the High Atlas in Morocco, Saharan Atlas in Algeria, and Tunisian Atlas in a similar way as it is fabulously imaged across the onshore and offshore Atlantic Moroccan basins.