Étude néotectonique de la région de Zighout Youcef analyse morpho structurale et photo interprétation .

Abstract

Actually, many scientists agree with the idea that slopes evolution depends mostly on lithological, topographic, climatic and anthropogenic factors. But, the results acquired from different neo tectonic studies in the Constantinois Tell (Raoult J.F., 1974, Marre A., 1987, Amireche H., 2001, Benabbas C., 2006) confirm that the relief deformation, mass movements and slops vulnerability depend also on the structural context. The active nature of north Algeria in general and the eastern Tell particularly increase the land movements related to relief deformations. These relief deformations are often connected to a morpho structural context marked by a neotectonic activity. The Zighout Youcef area is among the most deformed zones of the Constantinois Tell, where the geological structures associated with an active neotectonic and gravity movements are still poorly understood, which is necessary to know in details the structural context. With this study we would to clarify if the tectonic heritage is sufficient to trigger slops destabilization, and if the neotectonic is responsible for gravity hazard. In addition, these investigations will improve our understanding about the evolution of slopes in the recent geological period (from Mio Pliocene to present) and about the triggering process of ground movements, sometimes with vast amplitudes. For a better understanding of this problem, we carried out a study of geological and morpho structural features, based on mapping tool. We presented a detailed analysis of the horizontal and vertical relief evolution, based on the elevation maps analyses at different scales and completed with morpho geological cross sections. Besides, the relief analysis was coupled with aerial photography examinations. This remote sensing technique was established on a multi-source mapping, based on a correlation between the three information layers: aerial photography, geological maps and land topography, this aid to locate the recent geological structures and determine their involvement in the relief deformations and slopes instability. In parallel, X-ray diffraction mineralogical analyzes were carried out on the most affected soils by mass movements in order to determine the presence and influence of clays minerals on movements acceleration. The association of these research techniques allowed us to improve our knowledge about the geomorphological organization and the post orogenic structuration of Zighout Youcef area. The recent and current tectonic activity consolidates and control the relief deformations. The geological structures and the mountain aspect of this area, accelerate and even amplify the slopes instability.