Palynology, palynofacies and palaeoenvironment of the Serpukhovian Tazlourt Formation (Tinghir region, southern margin of the Variscan Zone, SE Morocco)

Abstract

The microfloristic study of limestones from the Tazlourt Formation in the Tinghir region, led to the first discovery of miospores of herbaceous and sub-arborescent lycopsids small fern and sphenopsids belonging to both non-forest mire and forest mire. The palynological assemblage also includes rare marine phytoplankton (i.e. Lophosphaeridium spp.). Among the continental palynomorphs, significant marker taxa, such as Grandispora spinosa, Dictyotriletes bireticulatus, Cirratriradites cf. C. rarus, Schulzospora cf. S. campyloptera and Punctatisporites gretensis enable a confident attribution to the upper Serpukhovian stage (the subtriquetra–ornatus or SO miospore Zone of the Western Europe). This proves the presence of uppermost Mississippian deposits at the southern front of the Moroccan Variscan chain. The kerogen released by the analyzed samples is predominantly of continental origin, mainly composed of opaque phytoclasts with different sizes and shapes, while translucent phytoclasts and miospores are less represented. The analysis of microfacies, as well as the qualitative and quantitative parameters of the various components of the palynofacies, indicates a shallow to moderately deep neritic environment and supports the existence of a connection to the “Variscan Sea” between the Anti-Atlas domain, located on the northwestern margin of the stable Gondwana craton, and the Moroccan Hercynides, situated at the southwestern margin of the Variscides. The miospores are characterized by significant alteration in texture and color, with Spore Color Index (SCI) values ranging from 7 to 9 and advanced silicification. This is likely related to the combination of tectonic events that affected the study area during the Meso- and Post-Variscan phases.