Preuves d’extensions flexurales dans l’avant-pays rifain : le bassin du Rharb-Mamora (Nord Maroc)

Le bassin du Rharb représente l’avant-pays de la Cordillère du Rif. La Mamora (nord du Maroc) correspond à la bordure méridionale de ce bassin entre les nappes pré-rifaines alpines au nord et la Meseta hercynienne au sud. La Mamora, largement couverte par des formations actuelles, l’analyse du potentiel des ressources naturelles, leur exploitation et leur gestion cohérente nécessitent une bonne connaissance des diverses formations et de leurs structures. L’analyse et l’interprétation de profils sismiques, de forages hydrogéologiques et pétroliers ont permis de préciser les structures majeures de la Mamora, largement recouvertes par des sédiments néogènes. La structure de cette région est contrôlée par des failles au moins hercyniennes, bien connues dans le substratum paléozoïque. Les deux grandes familles, NE-SW et NW-SE, ont contrôlé l’évolution paléogéographique (répartition des faciès et variations de la puissance des formations). La faille majeure dans cette région est la faille Kénitra – Sidi-Slimane (FK2S) [Zouhri et al., 2001]. Cette faille N110oE, à fort pendage N, est localisée au S du front de la nappe pré-rifaine dont l’amortissement est aveugle. Elle se traduit par un effondrement progressif vers le N. Il pourrait s’agir d’une réplique de la faille Rabat – Tiflet. La Mamora apparaît ainsi comme une charnière entre le Rharb subsident et la Meseta marocaine stable depuis le Mésozoïque

Etude hydrogéologique des séries triasiques dans la région de Jeffara-Dahar (Sud Tunisien): Apport des diagraphies et de la sismique réflexion

The present study concentrates on the interpretation of well logs and seismic reflection data in the Jeffara- Dahar region (Southeast part of Tunisia) for a better characterization of the Triassic aquifer, a potential target of water supply. Lithological columns and their corresponding well logs reveal that Sidi Stout, Kirchaou and Touareg sandstones as well as Mekraneb and Rehach dolomites are the main reservoirs of the Triassic aquifer. Well log analysis highlights many permeable and fractured layers that could play an important role in the groundwater circulation. The interpreted seismic sections and the resulting isochrone maps show a tectonic influence on the Triassic aquifer geometry in the Jeffara-Dahar region. The normal faulting of E-W and NW-SE accidents created an aquifer compartmentalized by raised and tilted blocks. Seismic cross-sections reveal that this structure controls the depth of permeable formations and the circulation of groundwater. These results will be useful for rationalising the future hydrogeological research that will be undertaken in the Jeffara-Dahar area.[fr] La présente étude concerne l’interprétation des données de la sismique réflexion et celles des puits y compris les enregistrements diagraphiques en vue d’une meilleure caractérisation de l’aquifère triasique de la région de Jeffara-Dahar (Sud-Est de la Tunisie) qui constitue une cible potentielle pour l’alimentation en eau. Les logs lithologiques associés aux enregistrements diagraphiques correspondants montrent que les principaux réservoirs sont les grés de Sidi Stout, Kirchaou et Touareg ainsi que les dolomies de Mekraneb et Rehach. L’interprétation diagraphique met en évidence des niveaux de faible perméabilité et d’autres perméables et bien fracturées qui pourraient jouer un rôle dans l’acheminement des eaux souterraines. Les profils sismiques interprétés et la cartographie élaborée en conséquence mettent en évidence que l’aquifère triasique est compartimenté en blocs soulevés et affaissés. Cette structuration, contrôlée par la réactivation des accidents E-W et NW-SE en failles normales au cours du Trias, influence l’épaisseur des formations perméables ainsi que le sens d’écoulement de la nappe d’eau. Les résultats obtenus seront utiles pour la rationalisation des futures recherches hydrogéologiques dans la région de Jeffara – Dahar

A New Pterosaur (Pterodactyloidea: Azhdarchidae) from the Upper Cretaceous of Morocco

The Kem Kem beds in South Eastern Morocco contain a rich early Upper (or possibly late Lower) Cretaceous vertebrate assemblage. Fragmentary remains, predominantly teeth and jaw tips, represent several kinds of pterosaur although only one species, the ornithocheirid Coloborhynchus moroccensis, has been named. Here, we describe a new azhdarchid pterosaur, Alanqa saharica nov. gen. nov. sp., based on an almost complete well preserved mandibular symphysis from Aferdou N'Chaft. We assign additional fragmentary jaw remains, some of which have been tentatively identified as azhdarchid and pteranodontid, to this new taxon which is distinguished from other azhdarchids by a remarkably straight, elongate, lance-shaped mandibular symphysis that bears a pronounced dorsal eminence near the posterior end of its dorsal (occlusal) surface. Most remains, including the holotype, represent individuals of approximately three to four meters in wingspan, but a fragment of a large cervical vertebra, that probably also belongs to A. saharica, suggests that wingspans of six meters were achieved in this species. The Kem Kem beds have yielded the most diverse pterosaur assemblage yet reported from Africa and provide the first clear evidence for the presence of azhdarchids in Gondwana at the start of the Late Cretaceous. This, the relatively large size achieved by Alanqa, and the additional evidence of variable jaw morphology in azhdarchids provided by this taxon, indicates a longer and more complex history for this clade than previously suspected

Modelling the impact of the climate change on the chalk aquifer resources (Northeastern France)

International audienc

A multicriteria approach for well drilling in productive zones of fissured systems.

International audienc

Etude géophysique et hydrogéologique du site minier abandonné de Kettara (région de Marrakech, Maroc): contribution au projet de réhabilitation

Abstract and keywords provided in French and EnglishLes rejets sulfurés de la mine abandonnée de Kettara, située à 30 km au Nord-Nord-Ouest de Marrakech, sont directement entreposés sur un substratum schisto-gréseux fracturé. D'une superficie d'environ 16 ha, ils constituent une réelle source de pollution pour l'écosystème local en particulier à cause du Drainage Minier Acide (DMA) vers les eaux de surface et de la nappe phréatique. Le projet de réhabilitation du site minier de Kettara prévoit dans l'un de ses axes de minimiser l'effet DMA par neutralisation à l'aide de dépôts stériles riches en carbonates issus de l'extraction des phosphates de la mine de Youssoufia voisine. Ces derniers seront utilisés à la fois comme amendement des rejets miniers acides et comme couverture évapo-transpirante (barrière capillaire). Notre étude a permis d'une part, de mieux appréhender la nature et la structure du parc à résidus et de son substratum et d'autre part, de caractériser l'impact de ces résidus sur la qualité des ressources en eau souterraine. Les résultats issus de cette étude vont contribuer à la réussite du projet de réhabilitation du site.The sulphurated mine waste of the abandoned Kettara pyrrhotite mine, located approximately 30 km north-northwest of Marrakech, Morocco, has been deposited on a fractured schistous substratum. Over an area of about 16 ha, this mine waste threatens the local ecosystem with pollution, particularly due to the infiltration of acid mine drainage (AMD) via surface waters towards the groundwater. As part of the rehabilitation project at the Kettara mine, it is proposed to minimize the effect of AMD by neutralization using fine sterile carbonate-rich deposits that are by-products of phosphate extraction in the neighbouring Youssoufia mine. These by-products are used both as amendement for the acidic mine waste and as a capillary barrier to allow evapotranspiration. On the one hand, our study has allowed a better understanding of the structure of the tailings pond and of the substratum, and on the other hand, it has made it possible to characterize the impact of the mine waste on groundwater quality. The results of this study will contribute to the success of the site rehabilitation project

Assessment of soil contamination around an abandoned mine in a semi-arid environment using geochemistry and geostatistics: Pre-work of geochemical process modeling with numerical models

International audienceOne of the most serious environmental issues related to mining industry in Morocco and elsewhere around the world, is the pollution from abandoned mine sites. Mine wastes cause obvious sources of soil contaminations. Climatic effects such as heavy rainfall engender metal dispersion in semi-arid areas, since soils are typically and scarcely vegetated. In this study, extension and magnitude of soil contaminations with toxic elements from abandoned Kettara mine, in Morocco, are assessed using geochemical analysis and geostatistics for mapping. Soils and mine wastes are sampled and analyzed for 41 chemical elements (Mo, Cu, Pb, Zn, Ag, Ni, Co, Mn, Fe, As, U, Au, Th, Sr, Cd, Sb, Bi, V, Ca, P, La, Cr, Mg, Ba, Ti, Al, Na, K, W, Zr, Ce, Sn, Y, Nb, Ta, Be, Sc, Li, S, Rb and Hf). Based on enrichment factor (EF), only five elements of interest (Cu, Pb, Zn, As, and Fe) were selected in this research. Geochemical background is determined with exploratory data analysis and geochemical maps were elaborated using geostatistics in Geographic Information System (GIS) environment.The obtained results show that Kettara soils are contaminated with metals and metalloid that exceed the established geochemical background values (Cu ≈ 43.8 mg/kg, Pb ≈ 21.8 mg/kg, Zn ≈ 102.6 mg/kg, As ≈ 13.9 mg/kg and Fe ≈ 56,978 mg/kg). Geochemical maps show that the deposited mine wastes are responsible for soil contaminations with released metals and metalloid that have been dispersed downstream from the mine waste mainly, through water after rainfall. For sustainable development and environmental planning, the current study is expected to serve as a reference for politicians, managers, and decision makers to assess soil contaminations in abandoned mine sites in Morocco

The pterosaurs of the Cretaceous Kem Kem Group of Morocco

The pterosaur assemblage of the mid-Cretaceous Kem Kem Group of Morocco is reviewed. This analysis examines their taxonomy, palaeoecology and palaeobiology with comments on taphonomy. New material permits the rediagnosis of the azhdarchoids Alanqa saharica and Afrotapejara zouhrii. Several specimens are reported that do not fit within the paradigms of previously named taxa. They represent three distinct jaw morphotypes, but are not assigned to new taxa here. The assemblage is highly diverse, including four tooth-bearing taxa assigned to Ornithocheiridae and five named taxa and three additional morphotypes assigned to Azhdarchoidea. The Kem Kem Group assemblage is the most diverse for any pterosaur-bearing fluvial deposit and one of the most diverse of any pterosaur assemblage. The assemblage is heavily biased in terms of preservation with an as yet unexplained high abundance of jaw fragments. We highlight the importance of fragmentary material in pterosaur studies.</p