Active transcurrent fault system along the north African passive margin

1987 ◽  
Vol 141 (1-3) ◽  
pp. 249-260 ◽  
Author(s):  
Zvi Ben-Avraham ◽  
Amos Nur ◽  
Cello Giuseppe
Keyword(s):  
Passive Margin ◽  
Fault System ◽  
North African ◽  
The North ◽  
Transcurrent Fault

The evolution of the Lansarine–Baouala salt canopy in the North African Cretaceous passive margin in Tunisia

2013 ◽  
Vol 150 (5) ◽  
pp. 835-861 ◽  
Author(s):  
AMARA MASROUHI ◽  
OLIVIER BELLIER ◽  
HEMIN KOYI ◽  
JEAN-MARIE VILA ◽  
MOHAMED GHANMI
Keyword(s):  
Geological Mapping ◽  
Passive Margin ◽  
Normal Faults ◽  
North African ◽  
The North ◽  
Extensional Tectonic ◽  
Two Factors ◽  
Salt Structure ◽  
Differential Sedimentation ◽  
Cretaceous Period

AbstractDetailed geological mapping, dating, and gravimetric and seismic data are used to interpret the Lansarine–Baouala salt structure (North Tunisia) as a salt canopy emplaced during the Cretaceous Period. The extensional tectonic regime related to the Cretaceous continental margin offered at least two factors that encouraged buried Triassic salt to extrude onto the sea floor and flow downslope: (i) extension induced normal faults that provided routes to the surface, and led to the formation of sub-marine slopes along which salt could flow; (ii) this structural setting led to differential sedimentation and consequently differential loading as a mechanism for salt movement. The present 40-km-long Lansarine–Baouala salt structure with its unique mass of allochthonous Triassic salt at surface was fed from at least four stems. The salt structure is recognized as one of the few examples worldwide of a subaerial salt canopy due to the coalescence of submarine sheets of Triassic salt extruded in Cretaceous times.

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

2014 ◽  
Vol 185 (5) ◽  
pp. 313-328 ◽  
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.

scholarly journals Revealing the earthquake history during the last 200 ka on a large submarine strike-slip fault: The Yusuf Fault System (Alboran Sea)

2020 ◽  
Author(s):  
Hector Perea ◽  
Eulàlia Gràcia ◽  
Stefanie Almeida ◽  
Laura Gómez de la Peña ◽  
Sara Martínez-Loriente ◽  
...  
Keyword(s):  
Complex Structure ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Fault System ◽  
Alboran Sea ◽  
North African ◽  
The South ◽  
Active Structures ◽  
The North ◽  
Alborán Sea

<p>The NW-SE convergence (4-5 mm/yr) between the African and Eurasian plates controls the present-day crustal deformation in the Alboran Sea (westernmost Mediterranean). Although seismic activity is mainly characterized by low to moderate magnitude events, large and destructive earthquakes (I > IX) have occurred in this region (i.e., 1522 Almeria, 1790 Oran, 1910 Adra, 1994 and 2004 Al-Hoceima or 2016 Al-Idrissi earthquakes). The identification and the seismogenic characterization of the active structures in the Alboran Sea using ultra high-resolution (UHR) geophysical data is essential to evaluate better the exposure of the South Iberian Peninsula and North African coasts to related natural hazards (i.e., large earthquakes and related tsunamis and triggered landslides). During the SHAKE cruise, the Asterx and Idefx AUVs (Ifremer, france) were used to acquire UHR bathymetric (1m grid) and seismic (cm vertical resolution) data across the main active faults systems in the Alboran Sea with the aim to carry out sub-aqueous paleoseismological studies. One of the studied active structures has been the Yusuf Fault System (YFS), a dextral strike-slip system that is one of the largest structures in the Alboran Sea and a lithospheric boundary between different crustal domains: the East Alboran Basin to the north and the North African Margin to the south. It trends WNW-ESE, is ~150 km-long and can be divided into two main segments (W and E), producing the formation of a pull-apart basin where both overlap. The analysis of the UHR geophysical dataset reveals that in the imaged area this system is a complex structure composed by an array of strike-slip faults. Most of them reach up and offset the seafloor and the upper Pleistocene to Holocene sedimentary units. The results of the on-fault paleoseismological analyses reveal that the YFS may have generated at least 8 earthquakes in recent times. Although a detailed on-site geochronology is not available, a regional chronostratigraphic correlation have allowed estimating that the events have occurred during the last 200 ka, then providing an average recurrence interval of 27.5 ka. The estimated average vertical offset is about 0.64 m while the vertical slip-rate would be around 0.03 mm/yr. However, this value needs to be considered as a minimum since YFS is predominantly a strike-slip fault and the lateral slip will be much larger than the vertical one. According to different empirical relationships, the YFS could produce earthquakes above magnitude M<sub>w </sub>7.0. Finally, our results demonstrate that detailed geomorphological, active tectonic and paleoseismological studies are essential to reveal the present-day activity and to characterize the seismic behavior of the YFS, with crucial implications for seismic (and tsunami) hazard assessment in the surrounding coastal areas.</p>

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

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

<p>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.</p><p>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 “Izzaren Duplex”. It attests for an important amount of shortening leading to the development of an imbricate fan of thrusts.</p><p>The geometry of the “Izzaren Duplex”, 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.</p><p>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.</p>

Skeletochronology and mark–recapture assessments of growth in the North African agamid lizard (Agama impalearis)

1999 ◽  
Vol 249 (4) ◽  
pp. 455-461
Author(s):  
El Hassan El Mouden ◽  
Mohammed Znari ◽  
Richard P. Brown
Keyword(s):  
North African ◽  
Mark Recapture ◽  
Agamid Lizard ◽  
The North

scholarly journals Defatted Hydroethanolic Extract of Ammodaucus leucotrichus Cosson and Durieu Seeds: Antidiabetic and Anti-Inflammatory Activities

2020 ◽  
Vol 10 (24) ◽  
pp. 9147
Author(s):  
Imane Es-Safi ◽  
Hamza Mechchate ◽  
Amal Amaghnouje ◽  
Anna Calarco ◽  
Smahane Boukhira ◽  
...  
Keyword(s):  
Wistar Rats ◽  
Fasting Blood Glucose ◽  
Diabetic Mice ◽  
North African ◽  
Glucose Levels ◽  
The North ◽  
Blood Glucose Levels ◽  
Anti Inflammatory ◽  
Hydroethanolic Extract ◽  
Inflammatory Effect

The seeds of Ammodaucus leucotrichus Cosson and Durieu have been used in the North African Sahara as a traditional medicine to treat diabetes. The present study investigates the antidiabetic, antihyperglycemic, and anti-inflammatory properties of the defatted hydroethanolic extract of Ammodaucus leucotrichus (DHEAM). The antidiabetic and the antihyperglycemic studies were assessed on alloxan-induced diabetic with orally administered doses of DHEAM (100 and 200 mg/kg). At the same time, its anti-inflammatory propriety was evaluated by measuring edema development in the Wistar rats paw induced with carrageenan. Treatment of diabetic mice with DHEAM for four weeks managed their high fasting blood glucose levels, improved their overall health, and also revealed an excellent antihyperglycemic activity. Following the anti-inflammatory results, DHEAM exhibited a perfect activity. HPLC results revealed the presence of seven molecules (chlorogenic acid, 3-p-coumaroylquinic acid, gallic acid, ferulic acid, myricetin, quercetin, luteolin). This work indicates that the DHEAM has an important antidiabetic, antihyperglycemic, and anti-inflammatory effect that can be well established as a phytomedicine to treat diabetes.

scholarly journals Identification and Characterization of the Most Common Genetic Variant Responsible for Acephalic Spermatozoa Syndrome in Men Originating from North Africa

2021 ◽  
Vol 22 (4) ◽  
pp. 2187
Author(s):  
Caroline Cazin ◽  
Yasmine Boumerdassi ◽  
Guillaume Martinez ◽  
Selima Fourati Ben Mustapha ◽  
Marjorie Whitfield ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
North Africa ◽  
Posterior Part ◽  
North African ◽  
The North ◽  
Transmission Electron ◽  
Variant Filtering ◽  
North African Population ◽  
Sperm Nuclei

Acephalic spermatozoa syndrome (ASS) is a rare but extremely severe type of teratozoospermia, defined by the presence of a majority of headless flagella and a minority of tail-less sperm heads in the ejaculate. Like the other severe monomorphic teratozoospermias, ASS has a strong genetic basis and is most often caused by bi-allelic variants in SUN5 (Sad1 and UNC84 domain-containing 5). Using whole exome sequencing (WES), we investigated a cohort of nine infertile subjects displaying ASS. These subjects were recruited in three centers located in France and Tunisia, but all originated from North Africa. Sperm from subjects carrying candidate genetic variants were subjected to immunofluorescence analysis and transmission electron microscopy. Moreover, fluorescent in situ hybridization (FISH) was performed on sperm nuclei to assess their chromosomal content. Variant filtering permitted us to identify the same SUN5 homozygous frameshift variant (c.211+1_211+2dup) in 7/9 individuals (78%). SUN5 encodes a protein localized on the posterior part of the nuclear envelope that is necessary for the attachment of the tail to the sperm head. Immunofluorescence assays performed on sperm cells from three mutated subjects revealed a total absence of SUN5, thus demonstrating the deleterious impact of the identified variant on protein expression. Transmission electron microscopy showed a conserved flagellar structure and a slightly decondensed chromatin. FISH did not highlight a higher rate of chromosome aneuploidy in spermatozoa from SUN5 patients compared to controls, indicating that intra-cytoplasmic sperm injection (ICSI) can be proposed for patients carrying the c.211+1_211+2dup variant. These results suggest that the identified SUN5 variant is the main cause of ASS in the North African population. Consequently, a simple and inexpensive genotyping of the 211+1_211+2dup variant could be beneficial for affected men of North African origin before resorting to more exhaustive genetic analyses.

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