Late Miocene to present-day exhumation and uplift of the Internal Zone of the Rif chain: Insights from low temperature thermochronometry and basin analysis |
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| Institution: | 1. School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK;2. School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK;3. British Antarctic Survey (BAS), High Cross, Madingley Road, Cambridge CB3 0ET, UK;4. University of Texas, Institute for Geophysics, Austin, TX 78758-4445, USA;5. Threshers Barn, Whitcott Keysett, Clun, Shropshire SY7 8QE, UK;6. NERC Isotope Geosciences Laboratories, Keyworth, Nottingham NG12 5GG, UK;7. Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK;8. Department of Geology, National Museum Cardiff, Cathays Park, Cardiff CF10 3NP, UK;1. Faculté Pluridisciplinaire de Nador & Laboratoire des Géosciences Appliquées, Faculté des Sciences, Université Mohammed I, Oujda, Morocco;2. Department of Geodynamics, University of Granada, Granada, Spain;3. School of Geosciences, University of Edinburgh, The King''s Building, James Hutton Road, EH9 3FE, Edinburgh, UK;4. Laboratoire de Géo-biodiversité et du Patrimoine Naturel (GEOBIO), Centre de Recherche \"Geophysics, Natural Patrimony and Green Chemistry\" (GEOPAC), Institut Scientifique, Université Mohammed V de Rabat, Morocco;5. John de Laeter Center, Curtin University, Bentley 6845, Australia;6. School of Earth and Planetary Science, Curtin University, Perth, WA, Australia;1. Departamento de Geodinámica, Universidad de Granada, 18002 Granada, Spain;2. School of Geosciences, University of Edinburgh, The King''s Building, James Hutton Road, EH9 3FE Edinburgh, UK;3. School of Earth and Planetary Science, John de Laeter Center, Curtin University, Bentley 6845, Australia;4. Departamento de Mineralogía y Petrología, Universidad de Granada, 18002 Granada, Spain;5. Departamento de Geología, Universidad de Jaén, Jaén, Spain;6. Departamento de Física de la Materia Condensada, Cristalografía y Mineralogía, Facultad de Ciencias, Universidad de Valladolid, C/ Paseo de Belén, 7, 47011 Valladolid, Spain;7. Departamento de Geodinamica, Estratigrafía y Paleontología, Universidad Complutense de Madrid, Madrid, Spain;1. UMR CNRS 5243 Géosciences Montpellier, Université Montpellier 2, CC 060, Pl. Eugène Bataillon, 34095 Montpellier, Cedex 05, France;2. Laboratoire des Géosciences Appliquées LGA, Université Mohamed 1er, faculté des sciences, Oujda, Morocco;3. UMR CNRS 5276 Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement, Université Claude Bernard Lyon 1, Boulevard du 11 Novembre 1918, 69622 Villeurbanne, Cedex, France;4. National Institute of Marine Geology and Geo-ecology (GeoEcoMar), Str. Dimitrie Onciul, nr 23-25, RO-024053, Bucharest, Romania;5. Muséum national d''histoire naturelle, département Histoire de la Terre, 8, rue Buffon, CP38, 75005 Paris, Cedex 05, France;6. Département de Géologie, Université Abdelmalek Esaadi, 93003 Tetuán, Morocco;7. Department of Historical Geology-Paleontology, University of Athens, Panepistimiopolis, 15784 Athens, Greece |
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| Abstract: | Located on the margin of the west Alboran basin, the Gibraltar Arc (Betic-Rif mountain belt) displays post-Pliocene vertical movements evidenced by uplifted marine sedimentary basins and marine terraces. Quantification of vertical movements is an important clue to understand the origin of present-day relief generation in the Betic-Rif mountain chain together with the causes of the Messinian Salinity Crisis. In this paper, we present the results of a pluridisciplinary study combining an analysis of low temperature thermochronology and Pliocene basins evolution to constrain the exhumation history and surface uplift of internals units of the Rif belt (Northern Morocco). The mean (U-Th)/He apatite ages obtained from 11 samples are comprised between 14.1 and 17.8 Ma and display a wide dispersion, which could be explained by a great variability of apatite chemistries in the analyzed samples. No correlations between altitude and age have been found along altitudinal profile suggesting a rapid exhumation during this period. Thermal modeling using our (U-Th)/He apatite ages and geochronological data previously obtained in the same area (40Ar/39Ar and K/Ar data on biotite, zircon and apatite fission track) allow us to propose a cooling history. The rocks suffered a rapid cooling at 60–100 °C/Ma between 22.5 and 19 Ma, then cooled to temperatures around 40 °C between 19 and 18 Ma. They were re-heated at around 110 °C between 18 and 15 Ma then rapidly cooled and exhumed to reach the surface temperature at around 13 Ma. The re-heating could be related to a renewal in thrusting and burying of the inner zones. Between 15 and 13 Ma the cooling resumed at a rate of 50 °C/Ma indicating an exhumation rate of 0.8 mm/y considering an average 40 °C/km geothermal gradient. This exhumation may be linked to the extension in the Alboran Sea. Otherwise biostratigraphic and sedimentological analysis of Pliocene basins of the internal Rif provided informations on the more recent events and vertical movements. Pliocene deposits of the Rifian coast represent the passive infilling of palaeo-rias between 5.33 and 3.8 Ma. The whole coastal area was uplifted at slow average rates (0.01–0.03 mm/y) in relation with a northeastward tilting of 0.2–0.3° since the Lower-Pliocene. A late Pliocene to present extensional tectonics associated to uplift has been identified all along the coastal ranges of the Internal Zone of the Rif chain. This extension was coeval with the major late Pliocene to Pleistocene extensional episode of the Alboran Sea and appears to be still active nowadays. No significant late Messinian uplift was evidenced, thus calling into question the geodynamic models relating the closure of the marine gateways and the MSC to slab roll back. |
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| Keywords: | LT thermochronology Basin analysis Vertical motions Rif Morocco Messinian Salinity Crisis |
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