Revised stratigraphic framework for the lower Anti-Atlas Supergroup based on U–Pb geochronology of magmatic and detrital zircons (Zenaga and Bou Azzer-El Graara inliers, Anti-Atlas Belt, Morocco)

Abdelhak Ait Lahna (1) , Nasrrddine Youbi (1, 2) , Colombo Celso Gaeta Tassinari (3) , Miguel Angelo Stipp Basei (3) , Richard Ernst (4) , Latifa Chaib (1) , Abdelhafed Barzouk (1) , João Mata (2) , Andreas Gärtner (5) , Hassan Admou (1) , Moulay Ahmed Boumehdi (1, 2) , Ulf Söderlund (6) , Mohamed Khalil Bensalah (1, 2) , Jean-Louis Bodinier (7) , Lhou Maacha , Andrey Bekker (8, 9)

1 UCA - Université Cadi Ayyad [Marrakech]
2 Instituto Dom Luiz
3 USP - Universidade de São Paulo = University of São Paulo
4 Carleton University
5 Senckenberg Naturhistorische Sammlungen Dresden
6 Skane University Hospital [Lund]
7 Géosciences Montpellier
8 UC Riverside - University of California [Riverside]
9 UJ - University of Johannesburg [South Africa]

U–Pb geochronology of magmatic and detrital zircons (Zenaga and Bou Azzer-El Graara inliers, Anti-Atlas Belt, Morocco) and a reassessment of the published constraints suggest a revised stratigraphic framework for the lower Anti-Atlas Supergroup. Five major unconformity-bounded lithostratigraphic packages are here distinguished: the two lower units of Paleoproterozoic age are named the Tasserda-Taghatine Group (2030–1706 Ma) and the Oumoula (Mimount) Formation (ca. 1745–1650 Ma); the third unit of Paleoproterozoic to Neoproterozoic age (ca. 1650 to >883 Ma) is the Tizi n’Taghatine Group; the fourth and fifth units of Neoproterozoic age are the ca. 883 Ma Tachdamt and the ca. 700 Ma Bleida formations. Implications of this revised stratigraphic framework include: 1) the Tasserda-Taghatine Group might be linked to the post-orogenic collapse after the Eburnean Orogeny; 2) the Tizi n’Taghatine Group might be ca. 1.1 Ga in age based on proposed correlation with the Taoudeni Basin succession in Mauritania; 3) the Bleida Formation likely reflects deposition in the foreland basin at the early stage of the Pan-African Orogeny; 4) the Oumoula (Mimount) Formation, Tizi n’Taghatine Group, and Tachdamt Formation potentially record extensional events within the Nuna/Columbia and Rodinia supercontinents; 5) the provenance of the lower Anti-Atlas Supergroup (based on our new detrital zircon dating) is mainly from the West African craton along with possible contributions from other cratons such as Amazonia and the Sahara Metacraton; 6) the flood basalt sequence of the Tachdamt Formation likely belongs to the ca. 885-883 Ma intraplate Iguerda-Taïfast Large Igneous Province (LIP) event defined by previously dated dykes in the Iguerda and Taïfast inliers; and 7) the 1650 Ma Zenaga LIP can be potentially linked with LIP magmatism in Baltica and Laurentia.

Mots clés: Morocco; Anti-Atlas Belt; Proterozoic; Lower Anti-Atlas Supergroup; U–Pb geochronology

Domaines: Stratigraphie

Abdelhak Ait Lahna, Nasrrddine Youbi, Colombo Celso Gaeta Tassinari, Miguel Angelo Stipp Basei, Richard Ernst, et al.. Revised stratigraphic framework for the lower Anti-Atlas Supergroup based on U–Pb geochronology of magmatic and detrital zircons (Zenaga and Bou Azzer-El Graara inliers, Anti-Atlas Belt, Morocco). Journal of African Earth Sciences, 2020, 171, pp.103946. ⟨10.1016/j.jafrearsci.2020.103946⟩. ⟨hal-03096023⟩