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The aim of the present study is to improve the knowledge of the Haouz basin structure using gravity data analysis. First of all, a residual anomaly map was computed from the Bouguer anomaly, greatly affected by an important regional gravity gradient. The calculated map provides information on the ground density variations mainly attributed to the top of the Paleozoic basement undulations under the sedimentary cover. However, in order to further study this map, it has been later analyzed with a method that allows evidencing different buried geological structures, combining the horizontal gradient and the upward continuations processing. The obtained results allows us to establish a structural map of the Haouz basin which confirms the existence of structures already recognized or assumed by the classic geological studies, and highlights accidents, as yet, unknown until the present time. This map shows that the fault system of the Haouz basin is organized in two families of directions NE-SW and NW-SE.Keywords: Gravity, contacts analysis, structure, Haouz, Marrakech, Morocco. 1 Techniques, BP. 549, Marrakech, Maroc. Email: elgouminajib@gmail.com 2 Ministère de l'Energie et des Mines, Rabat, Maroc. Estudios Geológicos, 66(2) julio-diciembre 2010, 181-191 ISSN: 0367-0449 doi:10.3989/egeol.40051.082 lées durant le Tertiaire et au Quaternaire d'importantes formations détritiques, résultant de l'érosion de la chaîne du Haut-Atlas mise en place lors de l'orogenèse atlasique ( fig. 2) (Ferrandini et Marrec, 1982). Ces formations reposent en discordance sur un substratum constitué d'un socle hercynien qui affleure à la faveur des massifs paléozoïques des Jebilets et des Guemassa. La structure de ces massifs anciens est relativement bien connue grâce aux nombreuses études dont ils ont fait l'objet en raison notamment de leur potentiel minier. Ces études sont souvent basées sur les observations classiques du terrain à l'échelle de l'affleurement, ou sur des techniques d'interprétation indirectes qui se sont développées au cours de ces dernières décennies, telle que l'analyse des images spatiales (Felenc et al., 1985; M. H. Boummane, 1987; J. Bamoumen, 1988;Leblanc, 1993;Hibti, 2001;El Harti et al., 2004). Laboratoire de Géoressources, Département des Sciences de la Terre, Faculté des Sciences etLa présente étude concerne le bassin du Haouz où ce genre d'étude demeure très limité, notamment, à cause du manque d'affleurements. Une reconnaissance de la structure de ce bassin est proposée en se basant sur l'analyse et l'interprétation des données gravimétriques. Contexte géologiqueL'histoire géologique du bassin du Haouz est marquée par la succession de plusieurs événements, initiés au mésozoïque, par l'arasement d'un socle paléo-zoïque fraichement structuré par l'orogenèse hercynienne. Ensuite, les jeux de failles et de flexures liées à des mouvements tectoniques tertiaires ont conduit à la mise en place d'une importante fosse entre le Haut-Atlas et les Jebilets ( fig. 1) (Essaifi et al., 2003). Plus au ...

Abstract. The present work is a combined study of gravity and Sentine-1 data for fracture mapping in the karstic massif of Beni Mellal Atlas and the adjacent plain of Beni Moussa. In order to locate the various faults that contribute to the study area structuring, the gravimetric contacts analysis method, based on the joint use of the horizontal gradient and the upward continuation at different altitudes, has been applied to the gravity data. To optimize the structural mapping in the study area, the gravimetric lineaments obtained were completed and correlated with the lineaments got from Sentinel-1 image. Four faults families of NE-SW; E-O; N-S and NW-SE directions have been highlighted. There fault families are perfectly combined with the studied area's surface water network, moreover, they corroborate with the previous geological and structural studies.

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The current study exposes the results of aeromagnetic data interpretation and a combined analysis of 1-A sentinel radar image that cover the study area of Beni Mellal Atlas in order to describe the structural geometry and to understand its tectonic evolution.The map of the reduced to pole of residual magnetic field highlights various magnetic anomalies with high amplitudes that correspond to Jurassic-Cretaceous basaltic formations outcropping synclinal basins of Beni Mellal Atlas. The interpretation of magnetic data using tilt derivative (TDR), horizontal gradient technique coupled to upward continuation and Euler Deconvolution allows us to distinguish the fractures network that is affecting the study area. In order to complete this analysis, the Sentinel-A radar image is processed and filtered using SNAP ESA Sentinel-1 toolbox software to extract lineaments. The final structural map reveals four faults groups oriented respectively NE-SW, ENE-WSW to E-W, N-S and NW-SE Their depths estimated by the application of Euler deconvolution exceed 1500 m.Thoses faults have played a major role in structural evolution of Beni Mellal Atlas.