A geological review of the Upper Carboniferous–Permian basins of Morocco: implications for paleoclimate and paleogeography

Abstract

The development of Upper Carboniferous to Permian basins in Morocco marks a key transitional phase between the waning Variscan orogeny and the onset of Alpine tectonics, offering critical insights into the configuration of Pangea. This study synthesizes sedimentological, tectonic, magmatic, and biostratigraphic data to refine the tectono-sedimentary and paleoclimatic evolution of these basins across the Western Meseta and the Paleozoic massif of the High Atlas. Traditionally considered products of a single tectono-sedimentary event, three diachronous depositional cycles are now recognized.

Cycle 1 (Upper Carboniferous) corresponds to the final stages of Variscan or pre-alpine phases deformation and is preserved in basins such as Sidi Kassem, Senhaja, and Oued Zat. It is characterized by grayish alluvial-fluvial deposits with thin coal seams rich in hydrophilic plants and the dominance of synapsid tracks, indicating humid conditions and strong faunal ties to Euramerica. Cycle 2 (Early Permian) developed during a pre-alpine transtensional phase with calc-alkaline magmatism. It features reddish fluvial-volcanic successions in basins like Khénifra and Mechra Ben Abbou. The spread of mesoxerophilous vegetation, dominance of anamniotes, and increasing reptile tracks alongside declining synapsid traces reflect seasonally dry to arid climates, yet continued Euramerican affinities. Cycle 3 (Middle–Upper Permian) reflects broader crustal extension and growing aridity, marked by alluvial and lacustrine carbonates in basins such as Koudiat El Hamra and Argana. The dominance of Reptile tracks confirm intensified aridity and biogeographic continuity.

Co-eval European basins underwent similar tectonic shifts from transtensional to extensional regimes. These changes aligned with a climatic trend toward increasing aridity and ecological adaptation. Fossil evidence confirms sustained biogeographic connections with Euramerica.