Fracturación asociada a pliegues en las calizas jurásicas de las cadenas del Sur del Rif (Marruecos)

The study of fractures affecting the Jurassic Ridges of Fert El Bir, Kefs and Outita from South Rifian Ridges, Northern Morocco, allowed us to propose a folding-fracturing model that summarizes the distribution of fractures within fault-propagation folds and the chronology of the different families of fractures occurring during the history of Miocene and Quaternary shortening phases, oriented NE-SW. At the beginning of compressional phase, sedimentary series corresponding mainly to limestones are deformed by layer parallel shortening (LPS) accompanied by pure shear causing thickening with the occurrence of oblique and transverse fractures. Following the establishment of the ramp fold, existing fractures are locally affected by simple shear within the two flanks of the fold and axial fractures are developed as a response of the accommodation of the surface foldingA partir del estudio de la fracturación en los materiales jurásicos de las estribaciones del sur de las cadenas rifeñas (norte de Marruecos), se propone un modelo de plegamiento y fracturación que explica la distribución de fracturas en pliegues de propagación de fallas, así como la cronología de las distintas familias de fracturas formadas durante la historia deformacional del Mioceno y Cuaternario (compresión NE-SW). Al comienzo de la etapa compresiva, las secuencias sedimentarias sufrieron una deformación por acortamiento paralelo a las capas (layer-parallel shortening, LPS), acompañada de cizalla pura que trajo como resultado el engrosamiento de las capas y la aparición de fracturas oblicuas y transversas. Después del emplazamiento del pliegue asociado a la falla, las fracturas sufrieron desplazamientos en los dos flancos del pliegue, y se formaron nuevas fracturas como resultado de la acomodación a la superficie de plegamient

Geologic interpretation of the aeromagnetic survey in the Agourai area (Central Morocco)

Abstract The aim of this work is to interpret the geologic structures of the Agourai area (Paleozoic and Mesozoic structures) from processed magnetic maps. The detected magnetic anomalies from different standard methods used in aeromagnetism (Residual map, RTP map, horizontal gradient map) were compared to geologic structures and permit enhancing the mapping quality of some areas, and thus defining many geologic features. Existing geologic maps and geologic field studies allow interpreting some detected anomalies. It was thus possible to define the limits between the Paleozoic basement and the Mesozoic cover, to determine magnetic anomalies according to NE-SW trends compatible with the regional geologic structures and finally to detect a NE to SW-oriented fault system in the Mesozoic cover of the Agourai Plateau. Despite the reliability of this approach, some folded basaltic sills occurring in this region were not well detected, probably because of their reduced thickness