We propose that they resulted from the partial melting of the base of a veined lithospheric mantle metasomatised during the late Cretaceous by alkaline melts from the Central Atlantic plume, the ancestor of the Canary plume. Melting was probably triggered by the flux of a hot mantle within a regional SW-NE sub-lithospheric channel, in. Recent analyses showed a decline in associated groundwater chemical quality and increased turbidity. To understand this hydrosystem, four surveys were undertaken during fall and spring, Five recharge zones of different altitudes have been defined, including two main mixing zones in the south.
A schematic conceptual model is presented to explain the groundwater circulation system and the behavior of this karst system. The elevation of the intra-continental Atlas Mountains of Morocco and surrounding regions requires a mantle component of buoyancy, and there is consensus that this buoyancy results from an abnormally thin lithosphere. Lithospheric delamination under the Atlas Mountains and thermal erosion caused by upwelling mantle have each been suggested as thinning mechanisms.
We use seismic tomography to image the upper mantle of Morocco by inverting teleseimic p-wave delay times, complemented with local delays, recorded on a dense array of stations in the Iberian peninsula and Morocco. A surface wave model provides constraint on the shallower layers. We propose discontinuous delamination of an intrinsically unstable Atlas lithosphere, enabled by the presence of anomalously hot mantle, as a mechanism for producing the imaged structures.
The Atlas lithosphere was made unstable by a combination of tectonic shortening and eclogite loading during Mesozoic rifting and Cenozoic magmatism.
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The presence of hot mantle, sourced from regional upwellings in northern Africa or the Canary Islands, enabled the mobilization of this lithosphere. Flow around the retreating Alboran slab focused upwelling mantle under the Middle Atlas , where we image the most recent delamination. The Atlas Mountains of Morocco stand as an example of mantle-generated uplift and large-scale lithospheric loss in a mildly contractional orogen.
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Miche, H. These waters are mainly renewed by the rainfall of L'Hajeb Causse and secondarily by the rainfall of Guigo Causse containing several springs. Hydrochemistry and saturation indexes allowed us to highlight two types of waters: a main contribution of Liasic origin and two low contributions of Triassic origin at the southern extremities SW, SE of the basin.
We pointed out the existence of five local recharge zones of different altitudes to m asl. Radon showed areas of rapid exchanges upwelling time less than two weeks between waters of Liasic aquifer and the ones of Triassic origin of high radon activity. The use of PCA on hydrochemical data, allowed us to refine the kind of waters, their transit times and highlighted the existence of several mixing zones between the Triassic aquitard and the Liasic aquifers in more or less faulted structures for the two causses. Previous campaigns of electrical resistivity tomography coupled with electromagnetic measurements EM34 revealed lateral and vertical variations of electrical conductivity changing with the depth along the North-South axis, and a preferential drain perpendicularly to the causses.
Hot upwelling conduit beneath the Atlas Mountains, Morocco. The Atlas Mountains of Morocco display high topography, no deep crustal root, and regions of localized Cenozoic alkaline volcanism. Previous seismic imaging and geophysical studies have implied a hot mantle upwelling as the source of the volcanism and high elevation. However, the existence, shape, and physical properties of an associated mantle anomaly are debated. Here we use seismic waveform analysis from a broadband deployment and geodynamic modeling to define the physical properties and morphology of the anomaly.
It includes a lateral conduit, which suggests that the Quaternary volcanism arises from the upper mantle. Moreover, the shape and temperature of the imaged anomaly indicate that the unusually high topography of the Atlas Mountains is due to active mantle support. 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. 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. 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. Environmental vulnerability and agriculture in the karstic domain: landscape indicators and cases in the Atlas Highlands, Morocco.
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Full Text Available After the brief presentation of the major karstic areas in Morocco , the article focused essentially on the Atlas mountains to investigate the impact of the agriculture on the natural systems equilibrium. Socio-economic changes demographic pressure, escalation of the landscape use, utilisation of new techniques in water harvesting, etc Many indicators seem to reflect these mechanisms. The pedologic indicators, soil erosion, the hydrologic and geomorphic indicators, are apprehended to demonstrate existent correlation between different variables and the often negative impacts of land over-use in the karstic domain of the Middle Atlas.
A stratigraphic study and mapping allow defining the particular features of this area of the southwestern Middle Atlas Morocco during the Toarcian and the Aalenian. Numerous spectacular variations in thickness and facies are documented by the discovery of coralline build-ups dated to the Late Toarcian. They occur along the palaeostructures. Development of the structures occurred in several stages: 1 initial differentiation during the Early and Middle Toarcian; 2 homogenisation during the Late Toarcian, after the construction of the reefs. These caused separation of several subbasins, which alternatively deepened and shallowed, probably due to the tilting of several blocks to the southwest.
To cite this article: F. El Hammichi et al. Geoscience Full Text Available An understanding of the interactions between climate change and forest structure on tree growth are needed for decision making in forest conservation and management. In this paper, we investigated the relative contribution of tree features and stand structure on Atlas cedar Cedrus atlantica radial growth in forests that have experienced heavy grazing and logging in the past.
Dendrochronological methods were applied to quantify patterns in basal-area increment and drought sensitivity of Atlas cedar in the Middle Atlas , northern Morocco. We estimated the tree-to-tree competition intensity and quantified the structure in Atlas cedar stands with contrasting tree density, age, and decline symptoms.
The relative contribution of tree age and size and stand structure to Atlas cedar growth decline was estimated by variance partitioning using partial-redundancy analyses. Recurrent drought events and temperature increases have been identified from local climate records since the s. We detected consistent growth declines and increased drought sensitivity in Atlas cedar across all sites since the early s.
Specifically, we determined that previous growth rates and tree age were the strongest tree features, while Quercus rotundifolia basal area was the strongest stand structure measure related to Atlas cedar decline. As a result, we suggest that Atlas cedar forests that have experienced severe drought in combination with grazing and logging may be in the process of shifting dominance toward more drought-tolerant species such as Q. The Tafilalt seismic crisis Anti- Atlas , Morocco. The review of data available on the seismic crisis allowed us to improve the knowledge on the macroseismic, instrumental and source parameters of the earthquakes.
The main results of the present study are: 1 location of the epicentres with the help of data from a close portable network allowed us to propose new epicentral coordinates at Imaging pockets and conduits of low velocity material beneath the lithosphere of the Atlas Mountains of Morocco : links to volcanism and orogenesis. Miller, M. The Atlas Mountains of Morocco have unusually high topography, with no apparent deep crustal root, and regions of localized Cenozoic alkaline volcanism. Previous seismic imaging and geophysical studies have implied a hot mantle upwelling as the source of the volcanism and high elevation, but the existence and physical properties of such an upwelling are debated.
We present results from S receiver functions SRF , shear wave splitting, waveform modeling, and geodynamic models that help constrain the tectonic evolution of the Atlas and the localized alkaline volcanism. These changes in lithospheric thickness also correspond to dramatic decreases in delay times inferred from S and SKS splitting observations. The shape, position and temperature of the imaged low velocity anomaly, offsets in the lithosphere-asthenosphere boundary, and correlation with mantle flow inferred from shear wave splitting suggest that the unusually high topography of the Atlas Mountains is due to active mantle support.
It is characterised by various petrographic facies including mafic rocks troctolites , intermediate rocks diorites, monzodiorites , and evolved rocks syenites , together with heterogeneous facies resulting from mixing between acidic and the intermediate magmas. Mineralogical and chemical data show i the transitional character of the Jurassic magmatic series of the Central High Atlas and ii the implication of continental crust as a contaminant during fractional crystallization.
To cite this article: R. Zayane et al. An ethnomedicinal survey of a Tashelhit-speaking community in the High Atlas , Morocco.
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Traditional knowledge about medicinal plants from a poorly studied region, the High Atlas in Morocco , is reported here for the first time; this permits consideration of efficacy and safety of current practises whilst highlighting species previously not known to have traditional medicinal use. Our study aims to document local medicinal plant knowledge among Tashelhit speaking communities through ethnobotanical survey, identifying preferred species and new medicinal plant citations and illuminating the relationship between emic and etic ailment classifications.
Ethnobotanical data were collected using standard methods and with prior informed consent obtained before all interactions, data were characterized using descriptive indices and medicinal plants and healing strategies relevant to local livelihoods were identified. Fidelity levels FL revealed low specificity in plant use, particularly for the most commonly reported plants. Most plants are used in mixtures.
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Plant use is driven by local concepts of disease, including "hot" and "cold" classification and beliefs in supernatural forces. Local medicinal plant knowledge is rich in the High Atlas , where local populations still rely on medicinal plants for healthcare. We found experimental evidence of safe and effective use of medicinal plants in the High Atlas ; but we highlight the use of eight poisonous species.
All rights reserved. Towards a better understanding of the Oulmes hydrogeological system Mid- Atlas , Morocco. Additionally, groundwater of the Oulmes plateau is intensively exploited for irrigation. The objective of this study, essentially performed from data collected during isotopic summer and piezometric and hydrogeochemical field campaigns spring , is to improve the understanding of the Oulmes hydro Three microbialite forms are recognized in the Lower-Cambrian succession of Irherm area in the western Anti- Atlas Morocco.
Stromatolites, which correspond to non-calcified shallow marine laminated microbialites, are well developed in the basal Lower-Cambrian succession. Occurrence of calcified microbial thrombolites, in the middle part of this succession, reflects an increasing sea level from the peritidal zone to the subtidal environment. In the upper part of this succession, a second increasing water depth event and the development of branching archaeocyathan reefal framework lead to dendritic microbialite emergence.
To cite this article: M. Benssaou, N. Hamoumi, C. Crustal structure under the central High Atlas Mountains Morocco from geological and gravity data. Ayarza, P. Seismic wide angle and receiver function results together with geological data have been used as constraints to build a gravity-based crustal model of the central High Atlas of Morocco. Integration of a newly acquired set of gravity values with public data allowed us to undertake Modelling suggests moderate crustal thickening, and a general state of Airy isostatic undercompensation.
Localized thickening appears restricted to the vicinity of a north-dipping crustal-scale thrust fault, that offsets the Moho discontinuity and defines a small crustal root which accounts for the minimum Bouguer gravity anomaly values. Gravity modelling indicates that this root has a northeasterly strike, slightly oblique to the ENE general orientation of the High Atlas belt.
A consequence of the obliquity between the High Atlas borders and its internal and deep structure is the lack of correlation between Bouguer gravity anomaly values and topography. Active buckling affecting the crust, a highly elevated asthenosphere, or a combination of both are addressed as side mechanisms that help to maintain the high elevations of the Atlas mountains. Triassic basalt of the Middle Atlas has been subject to metamorphic transformation then weathering.
Occurrence in both metabasalt and saprolite of ubiquitous clay minerals, such as smectite and mixed layers chlorite-smectite, makes it difficult to distinguish between the two alteration facies and explains the interest of complementary sources of information. In the Bhallil weathering profile, petrographical and mineralogical analyses of primary igneous minerals and their alteration products coupled with Fe oxidation state determination in clay fractions allow to identify three alteration facies: i metamorphic basalt, where iron occurs mainly as the ferrous form; ii the lower part of saprolite, where iron is partially oxidized to its ferric form; iii the upper part of saprolite, where iron is completely oxidized.
To cite this article: A. Dekayir et al. The velocity structure of the crust and the geometry of the Moho across Morocco has been the main target of two recently acquired wide-angle seismic reflection transects. Jointly these controlled source wide-angle seismic reflection data results in an almost km, seismic profile going from the the Sahara craton across the High and Middle Atlas and Rif Mountain till the Gibraltar-Arc Alboran. Current work on the interpretation of the seismic data-set is based on forward modeling, ray-tracing, as well as low fold wide-angle stacking.
The data has resulted in a detailed crustal structure and velocity model for the Atlas Mountains and a km transect revealing the irregular topography of the Moho beneath these two mountain orogens. Results indicate that the High Atlas features a moderate crustal thickness and that shortening is resolved at depth through a crustal root where the Saharan crust under-thrusts below the Moroccan crust, defining a lower crust imbrication which locally places the Moho boundary at, approximately, 40 km depth. The P-wave velocity model is characterized, in averaged, by relatively low velocities.