The eastern Amessoui Syncline – a hotspot for Silurian to Carboniferous cephalopod research

Abstract

Introduction : The Moroccan eastern Anti-Atlas comprises two large regions with vast outcrops of Palaeozoic rocks, the Maïder and Tafilalt (HOLLARD 1967, 1970, 1974), which have become world-reknown for Palaeozoic cephalopods, trilobites, and other groups (e.g. TERMIER & TERMIER 1950; MASSA 1965). Palaeogeographically, these regions correspond to the Maïder and Tafilalt Basins, which are divided by the south-north running Tafilalt Platform (WENDT et al. 1984; WENDT 1985, 1988; BAIDDER et al. 2016). This platform was submerged throughout the Silurian to Early Carboniferous and is characterized by often condensed, highly fossiliferous sedimentary sequences. Especially the Devonian succession (Fig. 1) crops out in a series of east-west oriented synclines. The largest of which was dubbed Amessoui Syncline after the mountain Jebel Amessoui (Fig. 2). At the western end of this syncline, the Devonian succession is much thicker than in the east because it was situated on the slope toward the Maïder Basin. In the eastern half of the syncline, the Middle to Late Devonian succession is much reduced in thickness because of the position on the Tafilalt Platform. The localities El Atrous, Filon 12, Jebel Ouaoufilal, Takkat Ou El Heyene, and El Khraouia are all situated on the former platform and accordingly are rich in pelagic fossil communities, especially cephalopods. In many layers, cephalopods occur in nearly rock-forming numbers, which can be considered as Konzentratlagerstätte sensu SEILACHER (1970, 1990). Here, we provide an overview of the cephalopod occurrences in the eastern Amessoui Syncline in their stratigraphic context.