Magnetic fabrics in the Jurassic–Cretaceous continental basins of the northern part of the Central High Atlas (Morocco): Geodynamic implications |
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| Institution: | 1. Department of Geobiology, University of Göttingen, Goldschmidtstraße 3, Göttingen 37077, Germany;2. Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK;3. Amber Study Group, c/o Geological–Palaeontological Museum of the University of Hamburg, Bundesstraße 55, 20146, Hamburg, Germany;1. Ludwig-Maximilians-Universität München, Department für Biologie I, Systematische Botanik und Mykologie, Geobio-Center, Menzinger Straße 67, 80638 München, Germany;2. Department of Geobiology, University of Göttingen, Goldschmidtstraβe 3, 37077 Göttingen, Germany;3. Mittlere Letten 11, 88634 Herdwangen-Schönach, Germany;4. Museum für Naturkunde, Leibniz-Institute for Evolution and Biodiversity Science, Invalidenstraße 43, 10115 Berlin, Germany;5. Amber Study Group, c/o Geological-Palaeontological Museum of the University of Hamburg, Bundesstraße 55, 20146 Hamburg, Germany;6. Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, Ludwig-Maximilians-Universität, und SNSB-Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Straße 10, 80333 München, Germany;7. Royal Botanic Gardens and Domain Trust, Mrs Macquaries Road, Sydney, NSW 2000, Australia;1. 503 Coxheath Road, Sydney, Nova Scotia B1R 1S1, Canada;2. Indiana Geological Survey, Indiana University, 611 N. Walnut Grove Ave., Bloomington, IN 47405 2208, USA;3. Centre for Palaeobiodiversity, West Bohemian Museum, Kopeckého sady 2, Pilsen 301 000, Czech Republic;4. Department of Natural Sciences (Botany Section) National Museum Wales, Cathays Park, Cardiff CF10 3NP, UK;1. Botanical Department of the Hungarian Natural History Museum, H-1476 Budapest, PO Box 222, Hungary;2. W. Szafer Botanical Institute, Polish Academy of Sciences, ul. Lubicz 46, 31-512 Kraków, Poland;3. Eötvös University, Biological Institute, Department of Plant Anatomy, Pázmány P. stny 1/C, H-1117 Budapest, Hungary |
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| Abstract: | The aim of this work is to study the Anisotropy of the Magnetic Susceptibility (AMS) in two Jurassic–Cretaceous synclines located in the northern border of the Central High Atlas (Morocco): the Aït Attab and Ouaouizaght basins. AMS is used in order to obtain the magnetic fabric and its relationship with the kinematic evolution of both basins. The tectonic evolution of the basins, still under discussion, is mostly considered as the result of inversion during Tertiary and perhaps since Bathonian, of extensional and/or strike-slip Jurassic basins. Both basins are filled with Upper Jurassic to Lower Cretaceous silts and sandstones, with less frequent marine marly limestones.The bulk magnetic susceptibility (km) generally shows higher values in the red facies (163.2 E?6 in AT and 168.6 E?6 in WZ) than in the yellowish marly limestones (97.88 E?6 in AT and 132 E?6 in WZ). Most sites show an oblate magnetic fabric. The rock magnetic analyses indicate that the main carrier of the magnetic susceptibility for the red facies is hematite, whereas in the yellowish facies there is a dominance of paramagnetic minerals. In both basins, the magnetic lineation (long axis of the ellipsoid, kmax axes) shows a predominant E–W direction. The overlapping of the stress fields during the Atlasic basins evolution, in both compressional and extensional regimes and hinder the straightforward interpretation of the magnetic fabrics. However, a coeval N–S compression during the times of sedimentation with an E–W transtension can explain the magnetic lineation found in many of the sites analyzed in the present work. There are also other less frequent directions of kmax axes (NE–SW and NW–SE) are interpreted as the result of local change of the stress field during the early extensional stage of basin formation. |
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| Keywords: | AMS Magnetic fabrics Jurassic–Cretaceous Continental sedimentary basin Red beds Central High Atlas |
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