Tectono-stratigraphic framework of the Proterzoic Tizi n'Taghatine Group (Anti-Atlas, Morocco): Evidence for a multiphase rifting on the northern margin of West African Craton

The Precambrian Anti-Atlas basin is a wide depositional structure lying along the northern margin of the West African Craton. The corresponding basin-fill strata formally named Tizi n’Taghatine Group is a volcano-sedimentary... [ view full abstract ]

The Precambrian Anti-Atlas basin is a wide depositional structure lying along the northern margin of the West African Craton. The corresponding basin-fill strata formally named Tizi n’Taghatine Group is a volcano-sedimentary succession which crops out in inliers of the central and western Anti Atlas. The complete succession of this group overlying the Eburnean basement is preserved in the central Anti-Atlas where it is bounded by a Panafrican suture. Recent field data combined with detailed mapping led to update the tectono-stratigraphic framework and the geodynamic setting of this Group and related pericratonic basin. The depositional and geodynamic history of the Anti-Atlas basin encompass two superposed basin-fill cycles linked respectively to the breakup of Columbia and Rodinia supercontinents. The two cycles are bounded by and unconformity with time gap of unknown duration.
The first basin-fill cycle deposited in a rift-related basin records two syn-rift phases. The initial rift phase consists of the Taghdout narrow graben, filled with clastic and carbonate shallow marine deposits of the Tasserda and Taghdout Formations, and crosscut by dolerites of Statherian age. The rift-climax phase consists of a wide rift basin extending over the whole central and western Anti Atlas. This phase corresponds to a thick siliciclastic continental and marine succession of the Oumoula Formation.
The second basin-fill cycle is preserved mainly in the central Anti-Atlas and partly in the western Anti-Atlas belt. This cycle with typical tripartite subdivision encompasses seven formations and records three stages. The first stage consists of a pre-rift succession made up of shallow carbonate and siliciclastic platformal deposits ranging from inner to middle ramp setting. The second stage correspond to the volcanic Tachdamt Formation which consists of thick mafic lava flows, with interbeds of hyaloclastites and pyroclastic lenses. This volcanic event records an early syn-rift phase which could be coeval with Tonian mafic dykes crosscutting the Eburnean basement. The overlying siliciclastic Bleida Formation consists of tempestites and turbidites, deposited in an outer to deep-shelf setting and contains minor interbeds of lavas flows and fine-grained pyroclastic layers. The Bleida sediments were deposited during the second syn-rift phase in an extensive network of grabens and in which hydrothermal fluids produced cooper deposits.
The tectono-sedimentary subdivision of the Tizi n’Taghatine Group indicate that the post Eburnean and prepanafrican Anti-Atlas basin preserves a succession with time span of Upper Paleoproterzoic to Middle Neoproterzoic and which records a multiphase rifting along the northern margin of West African Craton.