Thick-skinned tectonics in a Late Cretaceous-Neogene intracontinental belt (High Atlas Mountains, Morocco): The flat-ramp fault control on basement shortening and cover folding

Fekkak, Abdelilah; Ouanaimi, Hassan; Michard, André; Soulaı̈mani, Abderrahmane; Ettachfini, El Mostafa; Berrada, Ilyasse; Arabi, Hassan; Lagnaoui, Abdelouahed; Saddiqi, Omar

doi:10.1016/j.jafrearsci.2018.01.008

Cited by 47 publications

(18 citation statements)

References 83 publications

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“…(a) Cross section of the Amizmiz Plateau with main faults and location of the different photos (Figures b–d). Cross section is adapted from the fieldwork by Fekkak et al (). It details the section of Figure d, on a neighbor trace, and is slightly extended in the north compared to the trace of Figure d.…”

Section: Geological Settingmentioning

confidence: 99%

Polyphased Inversions of an Intracontinental Rift: Case Study of the Marrakech High Atlas, Morocco

et al. 2018

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The High and Middle Atlas intraplate belts in Morocco correspond to Mesozoic rifted basins inverted during the Cenozoic during Africa/Eurasia convergence. The Marrakech High Atlas lies at a key location between Atlantic and Tethyan influences during the Mesozoic rifting phase but represents today high reliefs. Age and style of deformation and the mechanisms underlying the Cenozoic inversion are nevertheless still debated. To solve this issue, we produced new low‐temperature thermochronology data (fission track and [U‐Th]/He on apatite). Two cross sections were investigated in the western and eastern Marrakech High Atlas. Results of inverse modeling allow recognizing five cooling events attributed to erosion since Early Jurassic. Apart from a first erosional event from Middle/Late Jurassic to Early Cretaceous, four stages can be related to the convergence processes between Africa and Europe since the Late Cretaceous. Our data and thermal modeling results suggest that the inversion processes are guided at first order by the fault network inherited from the rifting episodes. The sedimentary cover and the Neogene lithospheric thinning produced a significant thermal weakening that facilitated the inversion of this ancient rift. Our data show that the Marrakech High Atlas has been behaving as a giant pop‐up since the beginning of Cenozoic inversion stages.

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Section: Geological Settingmentioning

confidence: 99%

Polyphased Inversions of an Intracontinental Rift: Case Study of the Marrakech High Atlas, Morocco

et al. 2018

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“…Previous shortening estimates range from approximately 14 km in the FWHA (17–20%; Domènech et al, ; Fekkak et al, ) to 13–15 km in the WHA (15–21%;Domènech et al, ; Missenard et al, ; Teixell et al, ). We estimate the Cenozoic shortening in the WHA along a NNW‐SSE section (Figures a and b; details in the supporting information).…”

Section: Discussionmentioning

confidence: 99%

“…The structural evolution during the Cenozoic inversion is controlled by the reactivation of inherited structures with an important strike‐slip component (Fraissinet et al, ; Froitzheim et al, ; Laville & Pique, ; Laville & Piqué, ; Mattauer et al, ; Morel et al, ; Piqué et al, ). The kinematic of the inverted structures has been described (Amrhar, ; Dutour & Ferrandini, ; Ellero et al, ; Morel et al, 2000; Ouanaimi & Petit, ; Petit et al, ; Qarbous et al, , ) and synthesized by Fekkak et al (). Microstructural analyses indicate that the maximum compressive stress axis was horizontal and oriented approximately N‐S until the end of the Miocene and later turned to approximately NW‐SE (Amrhar, ; Qarbous et al, ).…”

Section: Geological Backgroundmentioning

confidence: 99%

“…The HA has been affected by several deformation phases from the Variscan orogeny to the Mesozoic rifting and the final Cenozoic compression (Ait Brahim et al, ; Frizon de Lamotte et al, ; Laville & Petit, ; Mattauer et al, , 1972; Piqué et al, ; Proust et al, ). Previous structural studies have indicated contrasting styles of Cenozoic compressional deformation in the HA (Amrhar, ; Dutour & Ferrandini, ; Ellero et al, ; Fekkak et al, ; Ouanaimi & Petit, ; Petit et al, ; Qarbous et al, , ). For example, studies in the western HA (WHA) have described it as both fold‐and‐thrust (Missenard et al, ) and oblique‐slip structures (Delcaillau et al, ; Ellero et al, ; Morel et al, 2000), whereas the central HA (CHA) has been described mainly as a fold‐and‐thrust belt (Arboleya et al, ; Teixell et al, ; Tesòn & Teixell, ).…”

Section: Introductionmentioning

confidence: 99%

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Tectonic Evolution of the Western High Atlas of Morocco: Oblique Convergence, Reactivation, and Transpression

et al. 2020

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The High Atlas of Morocco is a double-vergent mountain belt developed by Cenozoic shortening and inversion of a Triassic-Jurassic rift. The structural setting, the morphometric features, and the patterns of exhumation through time and space change remarkably both along and across the strike. Here we combine structural data with revised thermochronological data to unravel the kinematic and evolution of the western High Atlas. Our results show that the structural grain of the western High Atlas is defined by two main groups of faults, namely, thrust and oblique-slip faults, which mainly strike subparallel from W-E to NE-SW. The slip direction of the thrust structures is NNW-SSE to NW-SE oriented, and the slip direction of the oblique-slip faults is WSW-ENE to NW-SE oriented. Pieces of thermochronological and geological evidence indicate that in the last~10 Ma the exhumation rate increased during the activity thrusts and oblique-slip faults. The coexistence of these two fault systems also suggests partitioning of deformation under a transpressive regime. In the western High Atlas, we estimate a displacement of~12 km on the frontal thrusts and of at least~22 km on the axial oblique-slip structures. Thrusts and oblique-slip structures together result in a total cumulative displacement of~25 km, which represents about half of the Africa-Eurasia convergence.

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“…due to inversion of a Triassic‐Jurassic rift (Frizon de Lamotte et al, ; Gomez et al, ; Piqué et al, ; Teixell et al, ). Although shortening in the HA could have started as early as the Late Cretaceous (Domènech et al, ; Froitzheim et al, ; Hafid, ), its total amount remains moderate, between 12% and 35% (Arboleya et al, ; Beauchamp et al, ; Domènech et al, ; Fekkak et al, ; Gomez et al, ; Teixell et al, ). The high and rugged topography of the HA cannot be explained by shortening and crustal deformation alone; instead, it must be supported also by astenospheric processes, such as lithosphere thinning and/or delamination possibly associated with inflow of Canary mantle material (Arboleya et al, ; Duggen et al, ; Missenard et al, , ; Ramdani, ; Teixell et al, ).…”

Section: Introductionmentioning

confidence: 99%

Exhumation and Surface Evolution of the Western High Atlas and Surrounding Regions as Constrained by Low‐Temperature Thermochronology

et al. 2020

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The Moroccan High Atlas, the Anti-Atlas belts, and the Siroua volcanic massif form an orographic system locally risen to elevations over 4 km. Topographic growth of this system occurred by Cenozoic transpressive inversion of Mesozoic rift structures concomitant with volcanic activity and related mantle processes. In order to constrain the topographic growth, we analyze the regional-scale exhumation pattern, and we compare it to physiographic features. We contribute 35 new mean (U-Th-Sm)/He and 24 new fission track ages on apatite from the High Atlas and Anti-Atlas, which all together range from 196 to 5 Ma. In the Anti-Atlas, we find that the rate and amount of Cenozoic exhumation are <0.05 km/Ma and 2 km, respectively. In the High Atlas, our new data together with previous ones show that the axial regions feature the highest topography, relief, channel steepness, and orographic precipitations together with the maximum rate and amount of Cenozoic exhumation, in the range of 0.2-0.3 km/Ma and 4-6 km, respectively. This region is bounded by high-angle oblique-slip faults, which display a Neogene vertical motion of a few kilometers. Moreover, the most deeply incised valley in the axial region of the High Atlas shows stepwise cooling and exhumation with a final acceleration after 6 Ma. We conclude that the location in the same region of high river channel steepness, topography, orographic precipitations, and rates and amount of exhumation, together with large vertical offsets along oblique-slip faults, suggests that crustal deformation may exert a major control on the topographic growth of Atlas orographic swell.

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Thick-skinned tectonics in a Late Cretaceous-Neogene intracontinental belt (High Atlas Mountains, Morocco): The flat-ramp fault control on basement shortening and cover folding

Cited by 47 publications

References 83 publications

Polyphased Inversions of an Intracontinental Rift: Case Study of the Marrakech High Atlas, Morocco

Polyphased Inversions of an Intracontinental Rift: Case Study of the Marrakech High Atlas, Morocco

Tectonic Evolution of the Western High Atlas of Morocco: Oblique Convergence, Reactivation, and Transpression

Exhumation and Surface Evolution of the Western High Atlas and Surrounding Regions as Constrained by Low‐Temperature Thermochronology

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