Abstract
An interdisciplinary study based on lithostratigraphic, biostratigraphic, petrographic and mineralogical analyses has been performed in order to establish the Cenozoic tectono-sedimentary evolution of the El Habt and Ouezzane Tectonic Units (External Intrarif Subzone, External Rif, Morocco). The reconstructed record allowed identification of the depositional architecture and related sedimentary processes of the considered units. The Cenozoic successions were biochronologically defined allowing, at the same time, identification of unconformities and associated stratigraphic gaps. The presence of five unconformities allowed for the definition of the main stratigraphic units arranged in a regressive trend: (1) lower Paleocene interval (Danian p.p.) assigned to a deep basin; (2) Eocene interval (lower Ypresian-lower Bartonian p.p.) from a deep basin to an external carbonate-siliceous platform; (3) lower Rupelian-upper Chattian p.p. interval deposited on unstable slope with turbidite channels passing upward to an external siliciclastic platform; (4) Burdigalian p.p. interval from a slope; (5) Langhian-Serravallian p.p. interval from slope to external platform realms. The petrography of the arenites and calcarenites allowed for the identification of the supplies derived from erosion of a recycled orogen (transitional and quartzose subtypes). The clay-mineralogy analysis indicates an unroofing (first erosion of Cretaceous terrains followed by upper Jurassic rocks) always accomplished by erosion of Cenozoic terrains. Several tectofacies checked in some stratigraphic intervals seem to indicate the beginning of deformation of the basement generating gentle folds and first activation of blind thrusts, mainly during the Paleogene. A preorogenic tectonic framework is considered as responseto the generalized tectonic inversion (from extension to compression) as frequently registered in the central-western peri-Mediterranean areas. The large volumes of reworked terrigeneous supply during the latest Oligocene-Miocene p.p. indicates the beginningsof the synorogenic sedimentation (foredeep stage of the basins) controlled by active tectonics.
Highlights
The geology of Morocco [1] in the broad structural context of north-west Africa includes four main chains (Figure 1A): (1) the Pre-Cambrian Anti Atlas and the northern portion of the West AfricanCraton, (2) the Caledonian-Hercynian Moroccan Meseta, (3) the Middle and High intracontinentalAtlas, and (4) the Alpine Rif Chain, which record the effects of the Miocene-Quaternary deformation derived from the Maghrebian-Apennine orogenesis
The El Habt Unit is prevalently characterized by the widespread presence of thick quartzarenites, pelites and marly pelites, while the Ouezzane Unit is characterized by a wider diversity of lithofacies showing immature arenites, calcarenites and poligenic conglomerates
The mineralogy of the whole-rock and clay fraction was analyzed in 19 samples from the Ouezzane Unit in the DouarAhel Chane log in order to obtain preliminary data (Figure 3B)
Summary
The geology of Morocco [1] in the broad structural context of north-west Africa includes four main chains (Figure 1A): (1) the Pre-Cambrian Anti Atlas and the northern portion of the West African. (4) the Alpine Rif Chain, which record the effects of the Miocene-Quaternary deformation derived from the Maghrebian-Apennine orogenesis. Spain) constituting the Gibraltar Arc. Spain) constituting the Gibraltar Arc In this Betic-Riffian orogenic belt, three main paleogeographic domains and paleotectonic zones are represented (as in the rest of the Maghrebian chain) by different complex. These units have been recognized for a long time and derive from the deformation of three main paleogeographic domains: internal (nappes from continental margins), intermediate (nappes from the Maghrebian Flysch Basin located on prevalently oceanic crust) and external (Betic and Africa margins). Central-western Rif Chain (after [21], modified)
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