Ediacaran biota from Ougnat Massif (Eastern Anti-Atlas, Morocco): Paleoenvironmental and stratigraphic constraints

The Ediacaran period records the appearance of the first multicellular and complex organisms in Earth's history. Within the West African Craton, just a few simple discoidal structures have been previously reported within the supposed Ediacaran successions. Here, we describe for the first time a slightly diversified Ediacaran assemblage of micro- and macro-fossils from Ediacaran volcano-sedimentary rocks of Northwest Africa. Fossils occur in shallow water carbonate-bearing siliciclastic sediments of the Izelf Formation (567–550 Ma), in the Moroccan Anti-Atlas. Macrofossils are represented by Aspidella, ivesheadiomorphs and other problematic structures with putative biotic origin. The macrofossil assemblage is dominated by taphomorphs that indicate different degrees of preservation due to progressive decaying processes, possibly extending the effacement preservation mode outside of Avalonia assemblages. Microbially induced sedimentary structures (MISS), stromatolites and spheroidal microfossils are also reported. In particular, spheroidal microfossils may occur as isolated individuals or as concatenated spheres with potentially cell-division processes and were preserved through carbonate and silica permineralization. Morphologically, spheroidal microfossils are compared to sphaeromorph acritarchs and sulfur-oxidizing bacteria such as genus Thiomargarita. The depositional environment and age interval provide new information concerning paleogeographic and paleoenvironmental conditions of Ediacaran biota living on the West African Craton; thus, fills a gap in the Precambrian fossil record from the WAC.