Syn- to post-rift diapirism and minibasins of the Central High Atlas (Morocco): the changing face of a mountain belt

Abstract

The Atlas Mountains are classically regarded as a failed Mesozoic rift arm subject to Alpine inversion, folding and thrusting. Here, we present new integrated structural and sedimentological studies that have revealed numerous Early–Middle Jurassic diapiric ridges and minibasins, characterized by distinctive halokinetic structures. Diachroneity in halokinesis is observed across the Central High Atlas, waning first in the SW during the Early–Middle Jurassic (Jbel Azourki and Tazoult ridges) and continuing to late Middle Jurassic towards the NE (Imilchil region). The halokinetic structures are readily differentiated from the effects of later Alpine deformation, allowing a new picture of the Central High Atlas to emerge. The most pervasive deformation in the Central High Atlas is associated with Early–Middle Jurassic diapirism, whereas the impact of Alpine inversion is mostly focused at the basin margins. This new understanding helps explain previously problematic aspects of the Atlas Mountains, which we now recognize as an exceptionally well exposed natural laboratory for understanding the interactions between halokinesis, tectonics and sedimentation.

New numerical and theoretical model to characterize the upper crustal structure of the Moroccan atlas from wide-angle seismic reflection data

“…The maximum thickness of the sediments is clearly located beneath the Middle Atlas and the High Atlas featuring velocities around 4.5 km/s and 5.2km/s respectively at the surface, increasing to values of 5.3-5.4 km/s at the bottom of the layer reaching depths of 3 to 4 km. The highest velocities (around 5.2 km/s) are located beneath the High Atlas (at distances of 150-190 km) and match the geology mapped at surface and recent studies carried out in the area [39], [4], [5]. The High Atlas is mostly composed of Jurassic rocks, including carbonates, gabbros and Triassic evaporites and basalts that usually feature high P-wave velocities under these conditions of depth, pressure and temperature [40].…”

Rising and falling diapirs, shifting depocenters, and flap overturning in the Cretaceous Sopeira and Sant Gervàs subbasins (Ribagorça Basin, southern Pyrenees)

“…[]), (c) minibasin system in the Central High Atlas (modified after Saura et al . []), (d) restored Cotiella extensional system in the southern Pyrenees (modified from McClay et al . []), and (e) the Sivas Basin in Anatolia peninsula (modified from Callot et al .…”

“…Good quality seismic data allow interpreting the detailed geometry of diapirs and salt‐related minibasins even below allochthonous salt bodies [ Krzywiec , ; Ringenbach et al ., ; Hearon et al ., ], and the structure of the upper part of continental margins dominated by listric normal faults and hanging wall rollovers and rafts was typified. These salt tectonic concepts have led to the reinterpretation of odd structures in Alpine fold belts as potential salt‐related features in cases such as the Pyrenees [ McClay et al ., ; Canérot et al ., ], the SW Alps [ Graham et al ., ], the Central High Atlas [ Michard et al ., ; Saura et al ., ], and the Sivas Basin in Turkey [ Callot et al ., ] (Figure ). Within these settings, flaps or flap folds are understood as zones of upturned strata adjacent to a diapir, resulting from arching of the diapir roof above flanking strata [ Rowan et al ., ; Schultz Ela , ].…”

“…Continental margins and rifts are characteristic scenarios for salt basins and associated halokinetic systems [ Sannemann , ; Jackson et al ., ; Cobbold and Szatmari , ; Jackson and Talbot , ; Jackson and Vendeville , ]. These are frequently inverted and shortened by orogenic processes [ Letouzey et al ., ; Canérot et al ., ; Rowan and Vendeville , ; Saura et al ., ]. In such cases compressional overprinting may mask halokinetic structuration and eventually the diapiric stage may become completely obliterated.…”

The inverted Triassic rift of the Marrakech High Atlas: A reappraisal of basin geometries and faulting histories

“…1) linked with the Atlantic and Tethys opening (Choubert and Faure-Muret, 1962;Manspeizer et al, 1978;Van Houten, 1977). In the Marrakech High Atlas, preserved syn-rift Triassic sediments consist of red beds capped by volcanics (Beauchamp, 1988;Manspeizer, 1982), with an intervening diapiric evaporite layer evidenced in the Atlantic margin and in the Central High Atlas (Courel et al, 2003;Hafid et al, 2006;Saura et al, 2013;Tari et al, 2000).…”