A Late Pennsylvanian macrofloral assemblage from wetland deposits in Morocco (Senhaja, Basin): a taxonomic contribution with biostratigraphy and paleogeography implication

Abstract The sedimentary basin that overlies the deformed Variscan basement of the Moroccan Meseta has longtime been attributed to Pennsylvanian–Permian periods, largely based on lithological comparisons. We present a combined sedimentological and palaeontological study introducing a new palaeofloral assemblage from the Senhaja Basin in the Western Jebilet massif of Morocco. As a result, we refine the biostratigraphic age as most likely middle to upper Stephanian. Sedimentological data indicate that the floristic assemblage was fossilized in fine-grained sediments deposited in a lacustrine palaeoenvironment. The macroflora of the Senhaja Basin provides woods, branches, pith casts, leaves and seeds preserved as compressions and impressions in siltstone and claystone. The fossil assemblage consists mainly of tree ferns dominated by the fossil-genus Pecopteris, various Sphenopsids represented by arborescent forms such as Calamites axes, Asterophyllites and Annularia leaves and the herbaceous form Sphenophyllum. Cordaitaleans are represented by their Cordaites-type leaves and Cardiocarpus-type reproductive organs. Conifer leafy twigs were identified as Walchia. The taphonomic and sedimentological analyses allows recognition of two different taphofacies. Among them (1) lake deposits characterized by autochthonous and allochthonous elements in varied preservational condition, and (2) transverse bar deposits, which consist only of allochthonous elements showing higher mechanical degradation. The statistical distribution of the Senhaja Basin macroflora shows preominating pecopterids, accompanied by cordaitaleans and sphenopsids representing mostly hygrophilous communities, which grew in humid lowland areas. Conifer remains are rare but indicate surrounding xerophilous stands. In total, The Senhaja Basin exhibits a macroflora typical for coeval assemblages of the Late Pennsylvanian in Europe and North America.