Découverte de charophytes et ostracodes de l’Yprésien inférieur dans les Monts des Ksour (Algérie) : biostratigraphie et paléoécologie |
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Authors: | Abdelkader Mennad Mohammed Adaci Rodolphe Tabuce Carles Martín-Closas Madani Benyoucef Mustapha Bensalah Olga Otero Raphaël Sarr Djamila Zaoui |
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Institution: | 2. Université de Montpellier, Institut des Sciences de l’Évolution (UM, CNRS, IRD, EPHE), Place Eugène-Bataillon, 34095 Montpellier cedex 5, France;3. Departament de Dinàmica de la Terra i de l’Oceà, Facultat de Ciències de la Terra, Universitat de Barcelona - UB, Martí i Franqués s/n, 08028 Barcelona, Catalonia, Espagne;4. Faculté des Sciences de la Nature et de la Vie, Département des Sciences de la Terre et de l’Univers, Université de Mustapha Stambouli de Mascara, 29000 Mascara, Algérie;5. Laboratoire Paléontologie Evolution Paléoécosystèmes Paléoprimatologie (PalEvoPrim) ,UMR 7262 CNRS, université de Poitiers, Poitiers, France;6. Département de Géologie, Laboratoire de Sédimentologie et Biostratigraphie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar, B.P. 5005, Dakar-Fann, Sénégal |
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Abstract: | A stratigraphic, palaeontological and sedimentological study was carried out in the red beds cropping out on the left side of Oued Tafarahit, south-east of the Ksour Mountains (Algeria). The studied succession consists of a non-marine fining-upward detrital formation, including microconglomerate, sandstone and clay beds, which were previously attributed to the Cenozoic sensu lato, since no palaeontological evidence was available. Sedimentology suggests deposition in a fluvial environment. The clayey levels yielded the assemblage formed by the charophytes Peckichara atlasensis, Maedleriella cristellata, Nitellopsis (Tectochara) thaleri, Grovesichara sp., and Lamprothamnium papulosum and the ostracods Neocyprideis meguerchiensis, Herpetocypris? sp. and Cyprinotus? sp. This assemblage allows constraining the age of the detrital series from Oued Tafarahit to the Ypresian. Ostracods are typical of freshwater to euryhaline environments. The freshwater taxa (Herpetocypris? sp. and Cyprinotus? sp.) would indicate phases of desalinisation during periods of flood. However, the brackish water species (Neocyprideis meguerchiensis) is characteristic of saline phases related to low water table periods. Moreover the charophyte and ostracod assemblage confirms a close palaeobiogeographic relationship between North Africa and Southern Europe during the Lower Eocene. |
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Keywords: | Africa Saharan Atlas Ypresian Charophytes Ostracods Systematics Palaeobiogeography |
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