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Title: Magnetostratigraphy of the sedimentary fill of the Aïn Beni Mathar-Guefaït Basin (high plateau, E Morocco)
Authors: Parés, Josep María
Álvarez-Posada, Claudia
Pla-Pueyo, Sila
Benito-Calvo, Alfonso
Duval, Mathieu
Aouraghe, Hassan
Haddoumi, Hamid
Rodríguez-Hidalgo, Antonio
Oujaa, Aïcha
Agustí, Jordi
Chacón Navarro, María Gema
Sala, Robert
Issue Date: 2020
Publisher: American Geophysical Union
Abstract: The Aïn Beni Mathar-Guefaït Basin is located in the High Plateau Region (E Morocco). Along the northern margin of the basin, the upper Za River, which is the main eastern tributary of the Moulouya – the largest catchment in Morocco, incises more than 150 meters into Plio-Pleistocene sediments. The main goal of our study is to provide a geochronologic framework based on magnetostratigraphy and electron spin resonance (ESR) for the basin infill, which has implications on the age of the associated fauna, the evolution of the Moulouya River, and the activity of the faults that delimit the basin. The studied sedimentary rocks include flat-lying alluvial and lacustrine/palustrine deposits which have been sampled for magnetostratigraphy. Approximately a 140 m-thick section has been sampled on an average of 2.5 meters per site, and has produced a local magnetic polarity stratigraphy with nine geomagnetic reversals. Although no fold test is available, the presence of dual polarities and rockmagnetic analysis give us confidence that magnetization directions are primary. The obtained magnetozones have been anchored to the Geomagnetic Polarity Timescale (GPTS) using the biostratigraphic age and also local geological data. Our proposed magnetostratigraphy-based chronology reveals a sedimentary fill spanning from Gauss to Brunhes Chrons. The lower, detrital formations mostly fall within the normal Gauss Chron, whereas the upper lacustrine and palustrine carbonates, which are almost widespread to the top of the sedimentary fill, are upper Matuyama to Brunhes in age. These results provide the first chronological constraints for the basin fill in one of the largest intramontane basins of the High Plateau. The new magnetostratigraphy reveals that the major environmental change that triggered a switch from alluvial to lacustrine-palustrine conditions in Northern Maghreb occurred near the Matuyama-Olduvai reversal.
Description: Ponencia presentada en: American Geophysical Union, Fall Meeting Online, 1-17 de diciembre 2020
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Type: Presentation
Appears in Collections:Congresos, encuentros científicos y estancias de investigación

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