A missing link in the peri-Gondwanan terrane collage: the Precambrian basement of the Moroccan Meseta and its lower Paleozoic cover

Abstract

This article provides stratigraphic and geochronological data from a central part of Gondwana’s northern margin — the Moroccan Meseta Domain. This region, located to the north of the Anti-Atlas area with extensive outcrops of Precambrian and lower Paleozoic rocks, has hitherto not received much attention with regard to its Precambrian geology. Detrital and volcanic zircon ages have been used to constrain sedimentary depositional ages and crustal affinities of sedimentary source rocks in stratigraphic key sections. Based on this, a four-step paleotectonic evolution of the Meseta Domain from the Ediacaran until the Early Ordovician is proposed. This evolution documents the transition from a terrestrial volcanic setting during the Ediacaran to a short-lived carbonate platform setting during the early Cambrian. The latter then evolved into a rifted margin with deposition of thick siliciclastic successions in graben structures during the middle to late Cambrian. The detritus in these basins was of local origin, and a contribution from a broader source area (encompassing parts of the West African Craton) can only be demonstrated for postrifting, i.e., laterally extensive sandstone bodies that seal the former graben. In a broader paleotectonic context, it is suggested that this Cambrian rifting is linked to the opening of the Rheic Ocean, and that several peri-Gondwanan terranes (Meguma and Cadomia–Iberia) may have been close to the Meseta Domain before drifting, albeit some of them seem to have been constituted by a distinctly different basement.

Tectonic Evolution of the Eastern Moroccan Meseta: From Late Devonian Forearc Sedimentation to Early Carboniferous Collision of an Avalonian Promontory

“…Nevertheless, the paleogeographic relevance of these structures is unclear, since they do not include suture‐related rocks (e.g., ophiolites), and the Ordovician‐Devonian stratigraphic successions in all the Moroccan Variscides, as well as in other zones of the northern margin of Gondwana, indicate deposition in a shared passive margin (Piqué, 1994; Simancas et al, 2009), suggesting that all the domains of the Moroccan Variscides remained attached to northern Gondwana throughout the Paleozoic. This paleogeographic affinity is also supported by the detrital zircon provenance studies performed to date (Abati et al, 2010; Accotto et al, 2019; Avigad et al, 2012; El Houicha et al, 2018; Ghienne et al, 2018; Letsch et al, 2018), which suggest a Gondwanan provenance for the Cambrian to Devonian sediments of the Moroccan Variscides. The only exception would be the Sehoul Block in the Western Moroccan Meseta (Figure 1b), which is thought to have an Avalonian derivation based on the presence of a mid‐Paleozoic (i.e., Caledonian) deformation that occurred before the emplacement of granites radiometrically dated at the Late Devonian (U‐Pb on zircons; Tahiri et al, 2010).…”

The impact of the end-Ordovician glaciation on sediment routing systems: A case study from the Meseta (northern Morocco)

“…7), both possibly related to the magmatic (e.g., Caroff et al, 2009) and/or extensional events (e.g., Martinez-Catalan et al, 1992) affecting the north-Gondwana domain at the end of the Ordovician. The late Tonian population, which is absent from sample 15DL12 from Cambrian strata of Coastal Meseta (Letsch et al, 2018;Fig. 6), reflects the erosion of rocks exposed only after the Cambrian, which are possibly in relation with uplifts tied to the opening of Rheic ocean (Ouanaimi et al, 2016;Gärtner et al, 2017).…”

“…6), reflects the erosion of rocks exposed only after the Cambrian, which are possibly in relation with uplifts tied to the opening of Rheic ocean (Ouanaimi et al, 2016;Gärtner et al, 2017). The paucity of Cambrian zircon grains indicates that (i) Cambrian rift basins (Pouclet et al, 2008;Michard et al, 2010;Letsch et al, 2018) were buried at that time, and (ii) the Eburnean basement of the Meseta cannot be considered as a source for Paleoproterozoic zircon ages (e.g., El Houicha et al, 2018).…”

Detrital zircon U–Pb provenance and palaeogeography of Triassic rift basins in the Marrakech High Atlas

“…Detrital zircon U–Pb data available for Cambrian to Devonian strata of the Anti‐Atlas, Tindouf basin and Reguibat shield cover (Avigad, Gerdes, Morag, & Bechstädt, ; Gärtner et al., ) indicate a source area similar to that of the Neoproterozoic strata, with abundant detrital zircon ages related to the Pan‐African and Eburnean orogenic cycles and only very limited zircon grains related to the 2.73–2.20 Ga tectono‐thermal event and the Kibaran–Grenvillian orogenic cycle and >2.73 Ga zircon grains. To the north, detrital zircon U–Pb data from Cambrian sedimentary rocks of the Moroccan Meseta show a dominant Pan‐African signal with limited to absent age components related to other orogenic cycles (Letsch, Houicha, Quadt, & Winkler, ).…”