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An interval of episodic carbonate productivity, lithostratigraphically recognized as the ‘Calcaires inférieurs’ (upper member of the Adoudou Formation), took place across the Neoproterozoic–Cambrian transition onlapping the western Saghro inlier, Morocco. Sedimentation of the ‘Calcaires inférieurs’ was highly variable: in relatively stable substrates, a peritidal-dominated mixed platform is recorded where deposition was primarily controlled by autocyclic processes and accommodation space availability, whereas, in unstable substrates, the tectonic activity associated with the inherited block-faulting basement led to deposition of complex slide sheets composed of penecontemporaneous isoclinal folds and disrupted strata. The uppermost part of the ‘Calcaires inférieurs’ displays a negative δ13C shift reaching values of −6.5‰. This shift may represent the δ13C excursion to −6‰ that marks the Neoproterozoic–Cambrian boundary in the western Anti-Atlas. Two volcanic episodes bracketed the carbonate productivity. They consist of lower basaltic flows and an upper rhyolitic ignimbrite, with a SiO2 gap between 52 and 74 wt%. The basic rocks resemble those of tholeiitic magmas in continental rifts. The felsic rocks show high light to heavy rare earth element abundances and negative Nb, Ta, P and Ti anomalies, and were probably generated as a result of either fractional crystallization coupled with relative crustal contamination, or from a different magmatic source. The lower basic flows of tholeiitic affinity predated and geochemically differ from the alkaline magmatism of the Alougoum volcanic complex (Boho jbel) that surrounds the neighbouring Bou-Azzer inlier.

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The Late Neoproterozoic Ouarzazate Group crops out on the north margin of the West African craton (WAC). In this group an important post-collisional magmatism is characterized by a great diversity in plutonic and volcanic rock types of the high-K calc-alkaline series. This series evolved mainly by crystal fractionation and by an important crustal contamination from an anomalous mantle source. The Early Cambrian magmatism began at the same time on both sides of the Anti-Atlas Major Fault, the southwestern side (Kerdous region) and northeastern side (Ouarzazate-Agdz region), interbedded in the Early Cambrian Basal Series and spread later to the Western High Atlas of the Morocco northern WAC outboard areas. This magmatism changes from a continental tholeiitic series (HPT and LPT) at the beginning to an alkaline series at the top (Adoudou and ‘Lie de vin’ formations). Fractional crystallization and pelagic or crustal contamination were the most important processes in the magma differentiation. The geochemical inversion from calc-alkaline to tholeiitic magmatism between the Late Neoproterozoic and the Early Cambrian is documented, as is the major extension of the tholeiitic activity on both sides of the South Atlas Fault. This geochemical variation indicates a transition of the tectonic regime from compressive to extensional. The late local Jbel Boho alkaline magmatism indicates the sink of the source and the mitigation or closure of the extensional cycle at this time.