Caractéristiques et signification d'un niveau coquillier majeur à brachiopodes,marqueur événementiel dans l'évolution dévonienne de la Saoura (Sahara du Nord-Ouest,Algérie) |
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Authors: | Abdelkader Ouali Mehadji Serge Elmi Patrick Racheb?uf Larbi Mekahli |
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Institution: | 1. Laboratoire de magmatisme et géodynamique des bassins sédimentaires, université d''Oran Es-Sénia, BP 1524 El M''naouer Oran, Algérie;2. UFR des Sciences de la Terre, UMR 5125, université Lyon-1, 27–43, bd du 11-Novembre-1918, 69622 Villeurbanne cedex, France;3. UMR 6538, université de Bretagne occidentale, 6, av. Victor-Le-Gorgeu, BP 809, 29285 Brest cedex, France |
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Abstract: | In the Saoura, the brachiopod shell beds, so-called niveau coralligène, correspond to a major shell deposit dated to the Late Emsian. Brachiopods and crinoids dominate the benthic assemblage that contains also corals, bryozoans, trilobites, goniatites, and orthocones. This major level has a large geographic distribution and it is characterized by a wide brachiopod diversity due to time-averaging, taphonomic feedback and alternate bottom conditions changing from soft to shelly and firm. This kind of brachiopod association is linked to a transgressive onlap system. At regional extent, we can correlate this major shell bed to similar shell deposits from the Ahnet-Mouydir, Tindouf, and Zemmour areas. It indicates an important transgressive event underlined by change in the sedimentation from detritic deposits to carbonate sediments. To cite this article: A. Ouali Mehadji et al., C. R. Geoscience 336 (2004). |
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Keywords: | niveau majeur Sahara condensation rétroaction taphonomique Emsien supérieur major shell beds Sahara time-averaging taphonomic-feedback Upper Emsian |
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