The Rif mountain building (Morocco); a new tectonic scenario

Ahmed Chalouan; Andre Michard; Hugues Feinberg; Raymond Montigny; Omar Saddiqi

doi:10.2113/172.5.603

The Rif mountain building (Morocco); a new tectonic scenario

BSGF - Earth Sciences Bulletin ◽

10.2113/172.5.603 ◽

2001 ◽

Vol 172 (5) ◽

pp. 603-616 ◽

Cited By ~ 87

Author(s):

Ahmed Chalouan ◽

Andre Michard ◽

Hugues Feinberg ◽

Raymond Montigny ◽

Omar Saddiqi

Keyword(s):

Middle Miocene ◽

Accretionary Prism ◽

North African ◽

Data Set ◽

The North ◽

Mountain Belt ◽

Thrust Tectonics ◽

Rif Belt ◽

Latest Eocene ◽

Roll Back

Abstract The building of the Alpine Rif belt (southern limb of the Betic-Rif orocline) is restored, mostly based on the Tertiary stratigraphic and metamorphic data set. The Betic-Rif Internal zones derive from an exotic Alboran Terrane partly involved in a S-dipping Betic subduction during the Late Cretaceous ?-Eocene. Incipient collision of the terrane against Iberia triggered back-thrust tectonics south of the Internal mountain belt during the latest Eocene-Oligocene. A N-dipping Maghrebian subduction developed from that time up to Middle Miocene, responsible for the rifting of the internal Alboran Terrane. Docking of the extending Alboran Terrane onto the North African margin occurred during the Neogene through the closure of the Maghrebian Flysch oceanic trough, with southwestward growth of the external accretionary prism, and foredeep subsidence. Subduction zone westward roll back associated with delamination of the dense lithosphere seem to account for the Betic-Rif late orogenic evolution.

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Structural styles of the External Rif and Flysch Domain (Rif belt, northern Morocco) through thermal maturity and structural data

10.5194/egusphere-egu2020-19279 ◽

2020 ◽

Author(s):

Andrea Schito ◽

Achraf Atouabat ◽

Sveva Corrado ◽

Faouziya Haissen ◽

Geoffroy Mohn ◽

...

Keyword(s):

Vitrinite Reflectance ◽

Methodological Approach ◽

Structural Evolution ◽

Structural Data ◽

Thermal Modelling ◽

Thermal Maturity ◽

North African ◽

Data Set ◽

The North ◽

Rif Belt

Located in northern Morocco, the Rif belt represents the western edge of the Maghrebides system. This domain underwent a significant Cenozoic alpine compressional deformation, due to the collision between the North African margin and the south-western margin of the exotic Alboran Domain. This collision led to the development of a nappe stack during the Miocene.This contribution aims to characterize the main tectonic mechanisms driving the evolution of the Rifain wedge, its burial-exhumation paths and to understand the former architecture of the North African paleo-margin. The work focuses mainly on the Flysch domain, originated from the Maghrebian branch of the Tethys and on the External domain (namely Intrarif, Mesorif and Prerif) that belong to the former north African margin. To define the thrust sheet stacking pattern and their burial-exhumation paths, a regional transect from Chefchaouen and Ouezzane towns (Central Rif), crossing the orogenic wedge from the Flysch to the Prerif Units is constructed.The methodological approach consists in combining petrography and Raman micro-spectroscopy on organic matter and 1D thermal modelling, together with field structural data.A new paleo-thermal data set of vitrinite reflectance (Ro%) and Raman micro-spectroscopy displays levels of thermal maturity between early and deep diagenetic conditions (Ro% ranges from 0.50% to 1.15%).Preliminary results show an abrupt change in the thermal maturity and the rate of shortening in the Loukkos sub-unit (Intrarif Domain) that is structurally squeezed between Tangier sub-unit (Intrarif Domain) and the &#8220;Izzaren Duplex&#8221; (Mesorif).Furthermore, previous studies show that the thickest crust below the Rif fold-and-thrust belt is located below the Izzaren area, suggesting a deep crustal imbrication at the transition between the Intrarif and the Mesorif. These observations joined with the thermal maturity data and 1D thermal modelling allow revisiting the structural evolution of the central part of the Rif belt, by defining the rate of shortening and proposing a new geological restoration with respect to the Mesozoic North African margin structural original setting.

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How does the Alpine belt end between Spain and Morocco ?

BSGF - Earth Sciences Bulletin ◽

10.2113/173.1.3 ◽

2002 ◽

Vol 173 (1) ◽

pp. 3-15 ◽

Cited By ~ 157

Author(s):

André Michard ◽

Ahmed Chalouan ◽

Hugues Feinberg ◽

Bruno Goffé ◽

Raymond Montigny

Keyword(s):

Subduction Zone ◽

Plate Boundary ◽

Western Alps ◽

Late Eocene ◽

African Plate ◽

Northern Margin ◽

Thrust Tectonics ◽

Rif Belt ◽

Transitional Crust ◽

Roll Back

Abstract The Betic-Rif arcuate mountain belt (southern Spain, northern Morocco) has been interpreted as a symmetrical collisional orogen, partly collapsed through convective removal of its lithospheric mantle root, or else as resulting of the African plate subduction beneath Iberia, with further extension due either to slab break-off or to slab retreat. In both cases, the Betic-Rif orogen would show little continuity with the western Alps. However, it can be recognized in this belt a composite orocline which includes a deformed, exotic terrane, i.e. the Alboran Terrane, thrust through oceanic/transitional crust-floored units onto two distinct plates, i.e. the Iberian and African plates. During the Jurassic-Early Cretaceous, the yet undeformed Alboran Terrane was part of a larger, Alkapeca microcontinent bounded by two arms of the Tethyan-African oceanic domain, alike the Sesia-Margna Austroalpine block further to the northeast. Blueschist- and eclogite-facies metamorphism affected the Alkapeka northern margin and adjacent oceanic crust during the Late Cretaceous-Eocene interval. This testifies the occurrence of a SE-dipping subduction zone which is regarded as the SW projection of the western Alps subduction zone. During the late Eocene-Oligocene, the Alkapeca-Iberia collision triggered back-thrust tectonics, then NW-dipping subduction of the African margin beneath the Alboran Terrane. This Maghrebian-Apenninic subduction resulted in the Mediterranean basin opening, and drifting of the deformed Alkapeca fragments through slab roll back process and back-arc extension, as reported in several publications. In the Gibraltar area, the western tip of the Apenninic-Maghrebian subduction merges with that of the Alpine-Betic subduction zone, and their Neogene roll back resulted in the Alboran Terrane collage astride the Azores-Gibraltar transpressive plate boundary. Therefore, the Betic-Rif belt appears as an asymmetrical, subduction/collision orogen formed through a protracted evolution straightfully related to the Alpine-Apenninic mountain building.

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New ophiolite slivers in the External Rif belt, and tentative restoration of a dual Tethyan suture in the western Maghrebides

BSGF - Earth Sciences Bulletin ◽

10.2113/gssgfbull.185.5.313 ◽

2014 ◽

Vol 185 (5) ◽

pp. 313-328 ◽

Cited By ~ 22

Author(s):

André Michard ◽

Abdelkader Mokhtari ◽

Ahmed Chalouan ◽

Omar Saddiqi ◽

Philippe Rossi ◽

...

Keyword(s):

Oceanic Crust ◽

Suture Zone ◽

Passive Margin ◽

Transform Fault ◽

North African ◽

Structural Position ◽

Passive Margins ◽

The Core ◽

The North ◽

Rif Belt

AbstractOphiolite slivers have been described recently in the core of the External zones of the Central Rif belt. The present work aims at illustrating new ophiolite slivers further east and discussing the structural position and tectonic emplacement of all these oceanic floor remnants. Their basement consists of gabbros previously dated at 166±3 Ma and their cover includes mafic breccias, micrites and radiolarites. These oceanic slivers are located within the Mesorif nappe stack at the bottom of the Senhadja nappe that roots beneath the Intrarif Ketama unit and was thrust over the more external Mesorif and Prerif units during the Cenozoic inversion of the North African paleomargin. These oceanic crust (OC) slivers belong to the same Mesorif suture zone as the Beni Malek serpentinites and Ait Amrâne metabasites from eastern Rif that also include marbles with ophiolitic clasts and derive from an ocean-continent transition (OCT) domain. After examination of the varied hypotheses that have been suggested to account for the emplacement of these units in the External Rif, we propose that obduction sampled an oceanic corridor opened between the Mesorif and Intrarif domains at the emplacement of the Rif Triassic evaporite basin. The Intrarif block should have been then separated from the African passive margin and connected with the Flysch domain south of the passive margin of the Alboran domain. The pre-collision structure of the Rif transect would involve two hyper-extended passive margins separated by a narrow oceanic transform fault corridor. Therefore the Tethys suture in the western Maghrebides would be split by the Intrarif block and would involve the Flysch zone in the north and the ophiolite bearing Mesorif suture zone in the south.

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The structure of the Central-Eastern Rif (Morocco) and the disregarded subduction of the North-West African paleo-margin

10.5194/egusphere-egu2020-18249 ◽

2020 ◽

Author(s):

Oriol Gimeno ◽

Dominique Frizon de Lamotte ◽

Rémi Leprêtre ◽

Faouziya Haissen ◽

Achraf Atouabat ◽

...

Keyword(s):

Late Eocene ◽

West African ◽

North African ◽

Tectonic Event ◽

North West ◽

The North ◽

Before And After ◽

Rif Belt ◽

Thrust Sheets ◽

Gravity Driven

The Rif Belt (Northern Morocco) forms the western edge of the Alpine-Himalayan orogenic system developed during the convergence between the Africa and Eurasia plates. Compared to other mountains belts, the External Rif, which preserves remnants of the North African paleo-margin, presents two unusual features: (1) the presence of metamorphic massifs [External Metamorphic Massifs (EMMs)] and (2) the existence of large allochthonous thrust-sheets that travelled far away [the Higher Nappes]. In this contribution, we combined structural, stratigraphic and metamorphic data, complemented by new field observation and thermochronology results, to revisit the structure of the External Rif and to review its Cenozoic evolution. The External Rif was the site of a poly-phased tectonic evolution recorded before and after of a major unconformity: the so-called &#8220;Mesorif Unconformity&#8221; postdating an important Midde-Late Eocene deformation. This tectonic event is well-preserved in the North-African paleo-margin because of its under-thrusting (&#8220;subduction&#8221;) below the Maghrebian Tethys, the former oceanic domain separating Iberia from Africa. The MP-LT metamorphism, recorded in the EMMs (Temsamane Units in Morocco), is a direct vestige of this process.&#160; By contrast, traces of this event are absent in the oceanic units of the Intrarif Domain, element of the Maghrebian Tethys. After the &#8220;Mesorif Unconformity&#8221;, i.e. during the Miocene, the regional geodynamics is dominated by the westward translation of the Alboran Domain and the coeval deformation of the Ketama Unit (Intrarif) in front of it. This process results directly from the subduction of the Maghrebian Tethys, which happened at that time. The docking of the Ketama Unit against the already exhumed EMMs allowed an uplift and the subsequent detachment of the top of its lithostratigraphic pile, individualizing the Higher Nappes. During their gravity-driven travel towards the foredeep basin, they dragged at their floor the already exhumed Senhadja Nappes, inherited from the distal-most part of the NW African margin. All these elements are integrated in a coherent model integrating the External Rif in the geodynamics of the West Mediterranean.

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The Tunissian “zone des nappes”: a slightly inverted mesocenozoic continental margin (Taberka/Jendouba; northwestern Tunisia)

BSGF - Earth Sciences Bulletin ◽

10.2113/gssgfbull.177.3.145 ◽

2006 ◽

Vol 177 (3) ◽

pp. 145-154 ◽

Cited By ~ 31

Author(s):

Mohamed Abdoullah Ould Bagga ◽

Saâdi Abdeljaouad ◽

Eric Mercier

Keyword(s):

Continental Margin ◽

Middle Miocene ◽

Late Quaternary ◽

Original Model ◽

Early Miocene ◽

Thrust Faults ◽

North African ◽

Sedimentary Records ◽

The North ◽

Tunisian Atlas

Abstract Detailed investigations in the western part of the “zone des nappes” in the Tunisian Atlas enable to propose an original model for this area. We show that, according to sedimentary records, these units appear to be formed by various series originally deposited on tilted crustal blocks of the North African margin. This south-easternward tilting occurred from the Triasic to the early Miocene. The first phase of inversion took place during the early to middle Miocene interval; no older compressive event can be highlighted. The shortening is associated with a system of flats and ramps thrust faults that occurs following a piggy-back sequence and that does not disrupt the paleogeographic order. Subsequently, an “out-of-sequence” event places the upper unit (Numidian Unit) onto the sub-numidian Units. The overlap length remains very moderate betwen sub-numidian Units (a few kilometers only). Finally, during the late Quaternary, the area undergoes a late shortening that folds the syn-tectonic basins.

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Validating Structural Styles in the Flysch Basin Northern Rif (Morocco) by Means of Thermal Modeling

Geosciences ◽

10.3390/geosciences10090325 ◽

2020 ◽

Vol 10 (9) ◽

pp. 325

Author(s):

Achraf Atouabat ◽

Sveva Corrado ◽

Andrea Schito ◽

Faouziya Haissen ◽

Oriol Gimeno-Vives ◽

...

Keyword(s):

Vitrinite Reflectance ◽

Thermal Modeling ◽

Hydrocarbon Generation ◽

Thermal Maturity ◽

Data Set ◽

The North ◽

Frontal Part ◽

Rif Belt ◽

Thermal Indicators ◽

North Western

Vitrinite reflectance and a micro-Raman spectroscopy parameters data set have been acquired on dispersed organic matter of the Maghrebian flysch basin and the Tangiers unit across a NE-SW section in the north-western Rif belt (North Morocco). Thermal maturity shows increasing values from the hinterland to the external unit (from NE to SW). Paleo-thermal indicators show that the internal flysch basin (i.e., the Mauretanian unit) is less mature than the external one, (i.e., the Massylian unit), with Ro% and Ro eq. Raman values ranging from 0.64% to 1.02% (from early mature to late mature stages of hydrocarbon generation). 1D thermal modeling estimates the overburden now totally eroded ranging from 3.1 km to 6.0 km, and has been used as constraint to reconstruct the complete thrust wedge geometry in Miocene times. The reconstructed geometry accounts for high shortening (about 63%) due to the development of an antiformal stack in the frontal part of the wedge made up by the flysch succession. This stacking is interpreted as a consequence of the western translation of the Alboran Domain in the core of the Betic-Rif orogenic system.

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The structuration of the External Rif (Rif belt: Northern Morocco). An insights from paleo-thermal and structural analyses

10.5194/egusphere-egu21-12892 ◽

2021 ◽

Author(s):

Achraf Atouabat ◽

Sveva Corrado ◽

Dominique Frizon de Lamotte ◽

Geoffroy Mohn ◽

Faouziya Haissen ◽

...

Keyword(s):

Upper Cretaceous ◽

Vitrinite Reflectance ◽

Structural Evolution ◽

Structural Data ◽

Passive Margin ◽

Thermal Maturity ◽

North African ◽

Tectonic Structures ◽

The North ◽

Rif Belt

Belonging to the Maghrebides system, the Rif belt (Northern Morocco) suffered an important Cenozoic Alpine compressional deformation as a consequence of the closure of the Maghrebian Tethys and the westward translation and docking of the Alboran Domain onto the African margin during the Late Burdigalian. The Mesozoic North African Margin is still partially preserved in the Eastern Rif (e.g., Senhadja Jurassic-Cretaceous unit) and inverted in its Central portion (North of the Nekor Fault Zone) due to the high shortening in this area. It is in agreement with sub-surface data suggesting that the thickest crust along the chain is located in the central Rif (Izzaren Area, External Rif), and can be interpreted as a deep-rooted crustal imbrication.This contribution aims to characterize the role of the structural inheritance of the rifted North African margin in the development and the propagation of the Rif belt by the combination of paleothermal and structural data collected along a NE-SW regional transect (between Chefchaouen and Ouezzane provinces), focusing mainly on the external zones (namely, Intrarif, Mesorif and Prerif) sampling the deformed domains originally developed along the North African paleo-passive margin. A new paleo-thermal dataset of vitrinite reflectance (Ro%), micro-Raman spectroscopy on organic matter and XRD on clayey fraction of sediments displays levels of thermal maturity between early and deep diagenetic conditions (Ro% from 0.49% to 1.15%). The highest thermal maturity values along the section are concentrated in the Lower to middle Cretaceous Loukkos Intrarifain sub-unit that is structurally squeezed between Tangier Intrarif Upper Cretaceous sub-unit and the Mesorif &#8220;Izzaren Duplex&#8221;. It attests for an important amount of shortening leading to the development of an imbricate fan of thrusts.The geometry of the &#8220;Izzaren Duplex&#8221;, limited at surface by two first-order thrust faults, is controlled by pre-existing tectonic structures, probably inherited by the former architecture of the North African paleomargin. Moreover, the Chattian-Middle Miocene siliciclastic succession filling the Zoumi basin is in a stratigraphic continuity with the Izzaren Upper Jurassic-Upper Cretaceous substratum, sheding new light on its geodynamic meaning. This observation is supported by the homogeneity of deformation and the absence of thermal jump between the Mesozoic and Cenozoic successions, attesting for an active compressive deformation in the area between the Late Serravalian and Late Tortonian.In conclusion, the combination of paleo-thermal and structural analysis allowed to reconstruct robust tectono-thermal model in order to propose an accurate reconstruction of the structural evolution and a new geological restoration of the Rif belt with respect to the geometry of the rifted paleo-margin.

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