Structural styles of the western onshore and offshore termination of the High Atlas, Morocco

Hafid, Mohamad; Zizi, Mahmoud; Bally, A. W.; Salem, Abdallah Aı̈t

doi:10.1016/j.crte.2005.10.007

Cited by 91 publications

(100 citation statements)

References 29 publications

(71 reference statements)

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“…4A). Tying to boreholes allowed us to correlate Unit II with units Mo1-2 to Mo1-6 of Mridekh et al (2000) and Ng of Hafid et al (2006). In detail, and according to the nomenclature of Mridekh (2002), 4 sub-units can be distinguished; they correspond to Mo1-2 (Early Miocene), Mo1-3 (Middle Miocene), Mo1-4 (Late Miocene) and Mo1-5 to Mo1-6 (Pliocene and Quaternary).…”

Section: Seismo-and Tectono-stratigraphymentioning

confidence: 99%

“…-The Massa Front, trending mainly E-W, becoming WNW-ESE to the west. This structure corresponds to an anticline developed upon a blind thrust (Hafid et al, 2006), which can be interpreted as a fault-propagation fold, with a probable interference of salt (Mridekh et al, 2000). Genetically, the development of this fold in a corner may also be related to left-lateral strike-slip motion of the Tildi Marine fault.…”

Section: Structural Settingmentioning

confidence: 99%

“…Correlation to borehole data shows that Unit I corresponds to the Triassic, Jurassic, Cretaceous and Paleogene strata, particularly to seismic units Tr to Mo1-1 in the terminology of Mridekh et al (2000) and Tr to Pg of Hafid et al (2006)). In this unit, it is possible to observe regional-scale seismic horizons (Mridekh et al, 2000;Samaka, 2001;Mridekh, 2002), emphasized by strong reflectors, as those of the tops of the Triassic, the Jurassic, the Albian and the Cenomanian units ( fig.…”

Section: Seismo-and Tectono-stratigraphymentioning

confidence: 99%

“…, the Palaeogene and pre-Moghrebian (Pliocene) Neogene cover near Agadir was in great part eroded, except in a few locations, where the Maastrichtian beds are overlain by the Early Miocene "White Conglomerate" (Conglomérat blanc), the probable Messinian, and the Pliocene / Moghrebian formations (Allard et al, 1958;Duffaud, 1962;Ambroggi, 1963;Weisrock, 1980;Alonso-Gavilán et al, 2001). In the marine part, boreholes and seismic-reflection profiles performed since the latest 1970's (Flament-Lieffrig, 1979), and in particular during the last decade (Mridekh et al, 2000;Samaka, 2001;Mridekh, 2002;Hafid et al, 2006), have provided valuable information on the Cenozoic strata, because of their better preservation, frequently with a large thickness. The numerous structures mapped ( fig.…”

Section: Introductionmentioning

confidence: 99%

“…One of the most conspicuous structures in the area is the Kasba Fold Zone (zone des plis de la Kasba; Mridekh et al, 2000;Mridekh, 2002; hereafter abbreviated to KFZ), also called the "Elkasba monocline" (flexure d'Elkasba) by Hafid et al (2006), which is the northernmost offshore structure of the Agadir bay. Interpretation of the structures related to this fold zone suggests that, contrary to the emerged part of the western High Atlas, deformation seems to have been continuous in Tertiary times.…”

Section: Introductionmentioning

confidence: 99%

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Structure of the Kasbah fold zone (Agadir bay, Morocco). Implications on the chronology of the recent tectonics of the western High Atlas and on the seismic hazard of the Agadir area

Mridekh¹,

Medina²,

Mhammdi³

et al. 2009

Estud. geol.

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Detailed re-interpretation of the north-eastern segment of a profile realized across the Agadir bay along a NE-SW trend and crosscutting the main structures, together with analysis of available isochron maps, allowed us to retrace the geological history of the offshore western High Atlas. Two tectonostratigraphic sequences were distinguished: Unit II, which displays a simple structure, laying unconformably on Unit I, with a more complex structure dominated by a reverse fault (F1) striking E-W with a dip to the north. Correlation to boreholes Souss-1 and AGM-1 allowed us to assign Unit I to the Triassic – Palaeogene and Unit II to the Miocene – Present. The NE fault block shows a ramp-flat fault plane (F2) with an overlying SW-vergent fold that can be interpreted as a fault-bend fold. Three main stages were distinguished: (1) during the Cretaceous, F1 could have been a syndepositional normal fault with the NE block moving downwards; (2) towards the beginning of the Tertiary, the displacement of plane F2 induced the development of a fault-bend fold and erosion of the forelimb and hinge of the fold; displacement along F2 was transferred to fault F1; (3) afterwards, during the Miocene, reverse motion of F1 deformed and tilted the plane F2 and accentuated the folded structure. This evolution is typical for a frontal basin above a fault-related fold. Evaluation of the thickness and bed depth differences shows that the largest growth rate was recorded in Late Miocene times. Seismic activity recorded in the Agadir bay appears to be clearly related to this fault zone, as inferred from focal mechanisms. Seismic moment evaluation suggests that earthquakes of magnitude Mw≥6 are likely to occur, but could not be much larger because of the fault segmentation geometry of the High Atlas Front.<br><br>A partir de una detallada reinterpretación del segmento nororiental de un perfil que corta las principales estructuras de la bahía de Agadir a lo largo de una directriz NE-SW, y un análisis de los mapas de isocronas disponibles, se ha podido establecer la historia geológica de la costa del Alto Atlas occidental. En primer lugar, se han distinguido dos secuencias tectonoestratigráficas: la Unidad II, que muestra una estructura simple, y la Unidad I, de estructura más compleja dominada por una falla inversa (F1) de dirección E-W vergente al norte, sobre la que se dispone la Unidad II de forma discordante. La correlación con los sondeos Souss-1 y AGM-1 ha permitido asignar la Unidad I al Triásico-Paleógeno y la Unidad II al Mioceno-Presente. El bloque NE de la falla muestra un plano de falla de tipo rampa-rellano (F2) con un pliegue superpuesto vergente al SW que puede ser interpretado como un pliegue de flexión de falla. Respecto a su evolución temporal, se han distinguido tres estadios: 1) Durante el Cretácico, F1 pudo haber sido una falla normal sindeposicional, con el bloque NE desplazándose hacia abajo; 2) Al comienzo del Terciario, el desplazamiento del plano F2 indujo el desarrollo de un pliegue de flexión de falla y...

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Section: Seismo-and Tectono-stratigraphymentioning

confidence: 99%

Section: Structural Settingmentioning

confidence: 99%

Section: Seismo-and Tectono-stratigraphymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure of the Kasbah fold zone (Agadir bay, Morocco). Implications on the chronology of the recent tectonics of the western High Atlas and on the seismic hazard of the Agadir area

Mridekh¹,

Medina²,

Mhammdi³

et al. 2009

Estud. geol.

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Style of rifting and the stages of Pangea breakup

et al. 2015

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Pangea results from the progressive amalgamation of continental blocks achieved at 320 Ma.Assuming that the ancient concept of "active" versus "passive" rifting remains pertinent as end-members of more complex processes, we show that the progressive Pangea breakup occurred through a succession of rifting episodes characterized by different tectonic evolutions. A first episode of passive continental rifting during the Upper Carboniferous and Permian led to the formation of the Neo-Tethys Ocean. Then at the beginning of Triassic times, two short episodes of active rifting associated to the Siberian and Emeishan large igneous provinces (LIPs) failed. The true disintegration of Pangea resulted from (1) a Triassic passive rifting leading to the emplacement of the central Atlantic magmatic province (200 Ma) LIP and the subsequent opening of the central Atlantic Ocean during the lowermost Jurassic and from (2) a Lower Jurassic active rifting triggered by the Karoo-Ferrar LIP (183 Ma), which led to the opening of the West Indian Ocean. The same sequence of passive then active rifting is observed during the Lower Cretaceous with, in between, the Parana-Etendeka LIP at 135 Ma. We show that the relationships between the style of rifts and their breakdown or with the type of resulting margins (as magma poor or magma dominated) are not straightforward. Finally, we discuss the respective role of mantle global warming promoted by continental agglomeration and mantle plumes in the weakening of the continental lithosphere and their roles as rifting triggers.

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Magnitude of rift‐related burial and orogenic contraction in the Marrakech High Atlas revealed by zircon (U‐Th)/He thermochronology and thermal modeling

2016

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The Atlas of Morocco is a continental rift developed during the Triassic‐Jurassic and moderately inverted during the Cenozoic. The High Atlas south of Marrakech, with exposures of basement and Triassic early synrift deposits, has been viewed as a high during the Mesozoic rifting. First zircon (U‐Th)/He ages and thermal models obtained from 42 samples in the Marrakech High Atlas following two NNW‐SSE transects across the mountain belt reveal that in contrast to previous models, the Triassic‐Jurassic rift was well developed in the Marrakech High Atlas (with more than 4.5–6 km of rift‐related deposits). Middle Jurassic‐Early Cretaceous zHe cooling ages obtained indicate that rift‐related subsidence in the Marrakech High Atlas finished in the Middle Jurassic and was followed by a period of exhumation where 2–3 km of rock were eroded. Thermal models from zHe data provide the first thermochronologic clue for a Late Cretaceous initiation of the Atlas compression‐driven exhumation in the inner parts of the Marrakech High Atlas. The Triassic‐Jurassic basin reconstruction assisted by thermochronology highlights a key role of inherited basement anisotropy in rift orientation and evolution, and on its subsequent inversion. Comparison of present‐day and restored sections to the rifting stage aided by thermochronology suggests minimum values of total orogenic shortening in the Marrakech High Atlas of 13 to 14 km (21 to 17%), with exhumation of 1 to more than 5 km of rocks. Similar zHe ages on both sides of the Tizi n'Test fault evince minor vertical movements along the fault during the Atlas orogeny.

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Structural styles of the western onshore and offshore termination of the High Atlas, Morocco

Cited by 91 publications

References 29 publications

Structure of the Kasbah fold zone (Agadir bay, Morocco). Implications on the chronology of the recent tectonics of the western High Atlas and on the seismic hazard of the Agadir area

Structure of the Kasbah fold zone (Agadir bay, Morocco). Implications on the chronology of the recent tectonics of the western High Atlas and on the seismic hazard of the Agadir area

Style of rifting and the stages of Pangea breakup

Magnitude of rift‐related burial and orogenic contraction in the Marrakech High Atlas revealed by zircon (U‐Th)/He thermochronology and thermal modeling

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