Abstract
The Triassic-Jurassic basins of the High Moulouya area record the evolution of the Atlasicrifting in the SW-NE direction, showing a syntectonic continental sedimentation and an active volcanism. Such mobility has led to the differentiation of asymmetric half basins, whosegradual subsidence took place in successive stages. These basins, particularly during thedeposition of the terrigenous successions of the base of the Jurassic (early Liassic age),show a typical syntectonic continental infill. It consists of a mixed sedimentation, detrital andvolcanoclastic, generally coarse-grained towards the base. Coarser deposits, fed by volcanicclasts, are structured as sequences of spreading river cones, alternating with irregular clayfacies of flood plain. They reflect a rejuvenation of the relief, following a reactivation of thefaults. The sedimentary infill was provided by intermittent flows with considerable discharge,forming deposits along fault escarpments. The top of the terrigenous series shows a dominance of thin detritic sediments and a lack of volcanoclastics, reflecting the peneplanation ofthe relief and the creation of a flood plain. It records the widespread homogenization of theprior relief, causing the disappearance of the pre-existing structures during a period of tectonic quiescence. The volcanoclastics, witnessing an explosive volcanism and a concomitantsedimentation, are clustered in the tectonically active regions, where they are thicker and diversified. This late volcanism occurred during the final phases of rifting, owing to the replayof major Hercynian and tardi-hercynian faults. The Triassic-Jurassic period is thus marked byan extensional dynamics controlled by the influence of the first stages of the opening of thecentralAtlantic and the western Tethys
Highlights
The Triassic-Jurassic basins of the High Moulouya area record the evolution of the Atlasic rifting in the SW-NE direction, showing a syntectonic continental sedimentation and an active volcanism
Sanz de Galdeano base of the Jurassic, show a typical syntectonic continental infill. It consists of a mixed sedimentation, detrital and volcanoclastic, generally coarse-grained towards the base
Coarser deposits, fed by volcanic clasts, are structured as sequences of spreading river cones, alternating with irregular clay facies of flood plain. They reflect a rejuvenation of the relief, following a reactivation of the faults
Summary
En la región de Boumia-Tizi n’Rechou, las STL se desarrollan bien. Esta región se sitúa (Fig. 1) al SE de la falla de Aït Oufella, en el borde sur del Atlas Medio Meridional. Estos depósitos cambian lateralmente al NO (columnas Tt1 y TN) a ser lutitas plurimétricas de color rojo ladrillo, cubiertas por una alternancia de lutitas verdosas y de lentejones de arenisca o bien a areniscas gruesas con estratificación cruzada en artesa, organizadas en bancos pluridecimétricos entre los que se intercalan tobas laminadas rojas, tobas finas con geodas y lapilli gris calizas tobáceas, calizas silíceas y dolomías arenosas. Estos sedimentos están cubiertos por lutitas rojo-ladrillo con pasadas de tobas negras y de lutitas carbonatadas y laminadas, entre las que se intercalan conglomerados poligénicos con fragmentos centimétricos de basaltos y de carbonatos, microconglomerados con fragmentos centimétricos de calizas, lutitas verdosas y restos de basaltos, areniscas gruesas rojas y tobas con lapilli. Toda la región quedó definitivamente inundada tras el ascenso eustático del Sinemuriense superior, y en ella se instalaron ambientes perimareales, de plataforma marina interna, muy somera y restringida, y de marisma costera (Figs. 5, 6 y 7)
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