Biostratigraphic control of the latest-Ordovician glaciogenic unconformity in Alnif (Eastern Anti-Atlas, Morocco), based on brachiopods |
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Authors: | Enrique Villas Daniel Vizcaïno Jacques Destombes |
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Institution: | a Departamento de Ciencias de la Tierra (Paleontología), Universidad de Zaragoza, C/Pedro Cerbuna s. n., 50009 Zaragoza, Spain b 7, rue Jean-Baptiste Chardin, Maquens, 11090 Carcassonne, France c 19, rue de la Fon de Madran, 33600 Pessac, France d Sciences de la Terre, sciences Gabriel, bureau 8, 3e, 21000 Dijon, France |
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Abstract: | In the Alnif region of the Eastern Atlas (Morocco), seven fossiliferous horizons within the Lower-Ktaoua and Upper-Tiouririne formations (Ktaoua Group), as well as in the glaciomarine microconglomeratic shales of the Upper Formation of the Second-Bani Group have yielded biostratigraphically significant brachiopods and other taxa, such as trilobites and echinoderms. Several brachiopod species with short stratigraphic ranges, well-known in south-western Europe, allow a precise chronostratigraphic control of a succession that displays important lateral lithological and facies changes, when compared with the type sections in the Central Anti-Atlas. They have also permitted a better consensus between the macrofauna-determined age and that based on micropaleontological analyses. For the first time, the occurrence of a Hirnantia Fauna within the microconglomeratic shales of the Upper Formation of the Second Bani Group is reported. The biostratigraphic conclusions restrict the age of the Latest Ordovician glaciation to the early Hirnantian. |
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Keywords: | Brachiopods Biostratigraphy Glaciation Late Ordovician Morocco Northern Gondwana |
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