Detrital signatures of the Ghomaride Culm cycle (Rif Cordillera, N Morocco): New constraints for the northern Gondwana plate tectonics

Abstract

The Carboniferous detrital suites of the Ghomaride Subdomain (Rif Cordillera, N Morocco) has been undertaken in order to obtain paleogeographic and paleotectonic constraints. Microconglomerate and sandstone samples from eight sections belonging to four sectors were petrographically studied. This northern Gondwana domain was part of the Paleo-Mesomediterranean Plate, located between the Iberian-French Plates and the African Paleo-Atlas-Saharian Domain, which outlines a gap of knowledge since these domains are now part of the Alpine peri-Mediterranean chains. Part of this data-lacking is related to the sandstone detrital modes that have never studied in this area, allowing to obtain information about provenance derived from growing orogens, as well as orogenic processes, and tectonic, climatic and/or erosional events. The study has revealed that the sandstones are litharenites to feldsphatic litharenites, evolving upward to lithic arkoses, and has evidenced a quartzolithic petrofacies with a transitional recycled orogen provenance. The metamorphiclastic detritus displays a low to middle-upper metamorphic rank upwardly referred to a subducted terrane. Serpentinite-like detritus indicates a metamorphosed oceanic crust being dismantled. A supply from the Rheic Ocean seems improbable since it was very far and beyond the Iberian Plate. Therefore, closer oceanic sutures should be proposed, probably separating the Paleo-Mesomediterranean Plate from the Iberian-French Plate and from the Paleo-Atlas-Saharian Domain. The sin-sedimentary volcanic activity (felsic to mafic) reinforces the idea of subductions. A correlation with other Culm successions of the western Paleotethys has allowed the performing of a paleogeographic-paleotectonic model during the Paleotethysian tectonic phase, in which the studied sandstones were deposited in a foredeep connected northward with limestone platforms and with a crystalline emerged domain (hinterland-orogenic front: Iberia-French Plate and part of the Paleo-Mesomediterranean Plate) and transitioning southward to an oceanic branch of the western Paleotethys, and finally with the Paleo-Atlas-Saharian band acting as passive margin in the foreland.