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Jean-Paul Deroin, Université Paris-Est (France)
Souleye Wade, Université Cheikh Anta Diop (Senegal)
Papa Moussa Ndiaye, Université Cheikh Anta Diop (Senegal)
Mahamadane Diane, Université Cheikh Anta Diop (Senegal)
Abdoulaye Dia, Université Cheikh Anta Diop (Senegal)
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The Mauritanides fold belt extends from Morocco to Guinea Bissau over more than 2500 km. According to Villeneuve (2005), the central part, namely the central Mauritanides, lies from Akjoujt (Mauritania) to Kidira (Senegal) on the Faleme River. This area is particularly suitable for a remote sensing approach because of the arid and semi-arid conditions that allow the different lithologies of the substrate to be determined. We focus here on the area of Bakel, in the middle part of the Senegal River watercourse, a key area for understanding the structural framework and kinematics. The Pan-African and Paleozoic structures are well exposed due to the erosion of the Mesozoic-Cenozoic cover by the Senegal and Faleme River.
Landsat data have been selected because of their multispectral and multitemporal properties. Their digital processing includes geometrical rectification, spectral enhancement and embedding in a GIS data base. More advanced algorithms such as PCA analyses have also been performed. A set of four data has been monitored comprising a Landsat TM scene acquired on August 1984 and three Landsat ETM+ scenes acquired in October 1999, 2001, and 2002 respectively. August acquisition is clearly better because of driest conditions. October corresponds to the peak of precipitation and also to a lot of fire scars and some active fires. Then, the global intensity is weaker and correlation between the different infrared channels higher. Archived Landsat MSS data from the 1970's allow a global comparison of the biomass change during the last three decades. A biodiversity loss is clearly put into light in the region of Bakel-Kidira.
The different lithologies could be drawn, mainly quartzites (some of them are ferruginous), sandstones, conglomerates, micaschists, ultrabasites, diamictite, etc. We discuss the potential for discriminating each lithology and the interest of the different domain of the electromagnetic spectrum. The structural sketch enables new interpretations in term of tectonics of this segment of the Mauritanides belt.
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