4 research outputs found

    Pal√©oenvironnements de d√©p√īt et transformations post-sedimentaires des sables fauves du bassin du sais (Maroc)

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    The "Fawn sands" are constituted of detrital elements of quite complex history, reshaped from older and contemporaneous sedimentaries laterally settled. The different results obtained from the sedimentologic study executed on these sands confirm the marine nature of this formation.The age of sequence is specified by the Globorotalia crassaformis that gives middle Pliocene age. It's a series that registers the marine transgression of the middle Pliocene ("Moghrebien") caused by the relative rise in sea level in this era. The sea enters then into the region of Fez. The Sais basin constituted thus an open gulf to the west on the Atlantic ocean. The basin geodynamic evolution is related to the rise of the south-rif Ridges and the isostasie uplift of the meseto-atlasic domain. By another way, the Sais basin had been subsiding. The erosion of the young reliefs under a humid paleoc1imate leads to an increase of the detritic supplies. The filling up of the basin by sedimentary supplies associated with the lowering of relative sea level during the late middle Pliocene and the rise again of the El Kansara limit are the cause of the final sea recession of this basin. After the emersion, the warm and humid paleoclimate favored the development of aferralitic paleoalteration. The redistribution of the iron oxides by the phreatic and meteoric waters caused the marine sands marmorosis which allowed these sands to be called "Fawn sands".The paleoc1imate change, which becomes drier, induced continental deposit in which we have discovered larval Hymenopetra cells belonging to the ichnogenus Cellifonna.Les sables fauves sont constitu√©s d'√©l√©ments d√©tritiques √† histoire assez complexe, remani√©s √† partir de formations s√©dimentaires plus anciennes et contemporaines d√©pos√©es lat√©ralement. Les diff√©rents r√©sultats obtenus √† partir de l'√©tude sedimentologique effectu√©e sur ces sables confirment le caract√®re marin de cette formation. L'√Ęge de la s√©rie est pr√©cis√© gr√Ęce √† la pr√©sence de globorotalia crassaformis qui donne un √Ęge plioc√®ne moyen. C'est une s√©rie qui enregistre la transgression marine du plioc√®ne moyen (moghrebien) induite par la mont√©e relative du niveau de la mer √† cette √©poque. La mer avance alors vers l'E jusque dans la r√©gion de F√®s. Le bassin du sais constituait ainsi un golfe ouvert vers l'W sur l'oc√©an atlantique. L'√©volution g√©odynamique du bassin est li√©e √† la poursuite de l'exhaussement des rides sud-africaines et le soul√®vement isostasique du domaine meseto-atlasique. Par ailleurs, le sais √©tait subsident. L'√©rosion des reliefs jeunes sous un climat humide conduit √† l'augmentation des apports d√©tritiques. Le comblement du bassin par les apports s√©dimentaires conjugu√© √† la baisse relative du niveau de la mer √† la fin du plioc√®ne moyen et la mont√©e du seuil d'El Kansara √† l'W, sont √† l'origine du retrait d√©finitif de la mer de ce bassin. Apres l'√©mersion, le pal√©oclimat chaud et humide a favoris√© le d√©veloppement d'une paleoalteration de type ferralitique. La redistribution des oxydes de fer par la nappe phr√©atique et les eaux m√©t√©oriques conduit √† la marmorisation des sables marins qui est √† l'origine de leur appellation de sables fauves

    New Middle to ?Late Jurassic dinosaur tracksites in the Central High Atlas Mountains, Morocco

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    Besides bones, fossil tracks and trackways are important sources of knowledge about dinosaur palaeobiology. Here, we report three new tracksites from two different synclines in the Imilchil area, Central High Atlas, Morocco. The tracks and trackways are preserved in fluvial deposits in different levels of the Isli Formation (Early Bathonian‚Äď?Upper Jurassic), and contain impressions made by sauropods, theropods and ornithopods, as well as tracks that might represent bird-like non-avian theropod dinosaurs. In addition to traditional field measurements, three-dimensional digital models of the track sites were created using photogrammetry. These new tracksites add to the rich faunal ichnoassemblage already recorded from the High Atlas Mountains and North Africa, which is considerably richer than the contemporaneous body fossil record, and also provide new data on dinosaurs‚Äďsubstrate interactions

    Barremian intracontinental rift and Aptian Atlantic transgression in the northern boundary of the Central High Atlas (Morocco)

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    International audienceThe northern boundary of the Central High Atlas was affected by a transgression during the Aptian that reached the junction zone between the Middle and the High Atlas. In this sector (Naour-Aghbala) which corresponds to the presumed closure zone of this Aptian Atlantic marine trough, the sedimentary record reveals a strong dependence on the regional structural framework. The Barremian continental sedimentation is concentrated in an elongated W-E highly subsiding zone, limited to the south by the polyphase Aghbala-Afourer Fault Zone (AAFZ), which corresponds to the contact between the main Atlasic Belt and its northern boundary (Beni Mellal Atlas). The Aptian deposits preserve similar littoral marine characters from West to East without showing any confined facies, which could evoke the eastern limit of the gulf. On the other hand, towards the North, the Aptian layers rapidly change from marine to lagoonal then to continental facies. The paleogeographic boundary of the Aptian shoreline, oriented E-W, is locally controlled by the North El Ksiba Fault (NKF) in the North. The Aptian Atlantic transgression, closely linked to the narrow Barremian graben, shows a wide northward extension of the marine sedimentary area. The Barremian graben highlighted in the Aghbala-Naour area represents only a segment of a major east-west intracontinental rift that continued eastward with the more recent frontal thrust of the eastern Moroccan High Atlas. This faulted structure was the penetration axis of a double transgression: from the Tethys to the East and from the Atlantic Ocean to the West on the emerged Atlasic domain

    Electronic supplementary material from New Middle to? Late Jurassic dinosaur tracksites in the Central High Atlas Mountains, Morocco

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    Besides bones, fossil tracks and trackways are important sources of knowledge about dinosaur palaeobiology. Here, we report three new tracksites from two different synclines in the Imilchil area, Central High Atlas, Morocco. The tracks and trackways are preserved in fluvial deposits in different levels of the Isli Formation (Early Bathonian-? Upper Jurassic), and contain impressions made by sauropods, theropods and ornithopods, as well as tracks that might represent bird-like non-avian theropod dinosaurs. In addition to traditional field measurements, three-dimensional digital models of the track sites were created using photogrammetry. These new tracksites add to the rich faunal ichnoassemblage already recorded from the High Atlas Mountains and North Africa, which is considerably richer than the contemporaneous body fossil record, and also provide new data on dinosaurs-substrate interactions
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