Analyse multi-élémentaire par fluorescence X à dispersion d'énergie des apports fluviatiles et des sédiments superficiels de la plate-forme atlantique du Maroc

L'analyse multi-élémentaire d'une trentaine de sédiments d'oueds et de l'océan atlantique du Maroc a été réalisée en utilisant des spectromètres X à dispersion d'énergie et des sources radioactives d'excitation en Fer-55, Cd-109 et Am-241. Les échantillons ont été collectés de la plate-forme continentale atlantique, de Tanger à Agadir et des oueds situés entre ces deux villes. Les objectifs de cette analyse sont : * la caractérisation géochimique des sédiments en vue de l'approche du transfert de matière du continent vers l'océan en tenant compte des données morphologiques, climatiques et géologiques de l'environnement sédimentaire. Les échantillons ont été prélevés par benne de la plate-forme continentale atlantique et des lits des oueds suivants, du Nord vers le Sud : Tahaddart, Loukkos, Sebou, Bou Regreg, Oum er Rbia, Tensift et Souss. Les régions du Nord dont la plupart sont irriguées présentent un climat humide alors que celles du Sud ont un climat semi-aride à aride avec des oueds intermittents. * la détermination de pollutions possibles de la zone littorale en relation avec l'activité anthropique, principalement au large des zones urbanisées. la précision des résultats a été évaluée par l'analyse de deux matériaux standards de référence de 1'AIEA (Agence International de 1'Energie Atomique), le sédiment «SL-1» et le sol «soil-7». Cette précision est de 5% pour la plupart des éléments majeurs alors qu'elle n'est que de 10 à 20% pour les éléments traces.The XRF analysis of about 30 sediments from Moroccan oueds (rivers) and atlantic continental shelf for the content of major and trace elements has been performed, utilizing the energy dispersive X-ray spectrometer and radio-isotope excitation with Fe-55, Cd-109 and Am-241 annular sources. Samples have been collected from Moroccan atlantic continental shelf from Tanger to Agadir and oueds between these cities. The objectives of this analysis were : * to determine the geochemical areas on Moroccan atlantic continent, * to explain the mechanisms of sediment transport from the continent to the sea throw the oueds using morphological, climate and hiterland impacts. Thus, sample have been collected from atlantic continental shelf and the following oueds, from the north with a humid climate and irrigated areas to the south with a semi-arid to arid climate : Tahaddart, Loukkos, Sebou, Bou Regreg, Oum er Rbia, Tensift and Souss, * to assess the eventual pollution of the coast by human activities, mainly at regions which are very urbanized. Results were assessed for the accuracy by the analysis of standard reference materials from IAEA (International Atomic Energy Agency), soil-7 and SL-1 sediment. The results obtained for most of the major elements were accurate to about 5% while the accuracy of trace element determination was much worse, 10 to 20%

Spatial correlation between the predictor variables and the weighting values calculated during the mapping of the environmental factors of mass movements in the Beni Idder region (northern Rif)

The Tleta of Beni Ider region located in the SW of Tetouan (Rif Septentrional) knows many mass instabilities. The diagnostic via the inventory, the mapping and the characterization of mass movements was made by using satellite imagery, aerial photography and field data coupled with existing documents (geological, geomorphological,…). The understanding of both their spatial distribution and the mechanism generating them, is very complex because of the existence of an important number of natural factors (geological, geomorphological, hydrological) in a relative mountainous landscape with deep valleys, steep slopes and significant elevation changes. Thus, a multidisciplinary approach was adopted to elaborate the landslide susceptibility map of the region taking into account interactions and causal relationships between the various natural parameters that tend to accentuate and aggravate the setting of landslides. The multidisciplinary database allowed us to evaluate the susceptibility thanks to a bivariate probabiliste model (Weight of Evidence). The obtained landslide susceptibility map is a major contribution to the development of urban development plans in the region

Spatial correlation between the predictor variables and the weighting values calculated during the mapping of the environmental factors of mass movements in the Beni Idder region (northern Rif)

The Tleta of Beni Ider region located in the SW of Tetouan (Rif Septentrional) knows many mass instabilities. The diagnostic via the inventory, the mapping and the characterization of mass movements was made by using satellite imagery, aerial photography and field data coupled with existing documents (geological, geomorphological,…). The understanding of both their spatial distribution and the mechanism generating them, is very complex because of the existence of an important number of natural factors (geological, geomorphological, hydrological) in a relative mountainous landscape with deep valleys, steep slopes and significant elevation changes. Thus, a multidisciplinary approach was adopted to elaborate the landslide susceptibility map of the region taking into account interactions and causal relationships between the various natural parameters that tend to accentuate and aggravate the setting of landslides. The multidisciplinary database allowed us to evaluate the susceptibility thanks to a bivariate probabiliste model (Weight of Evidence). The obtained landslide susceptibility map is a major contribution to the development of urban development plans in the region