Spatio-temporal evolution of the Choisille River (southern Parisian Basin,France) during the Weichselian and the Holocene as a record of climate trend and human activity in north-western Europe |
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| Authors: | Eymeric Morin Jean-Jacques Macaire Florent Hinschberger Isabelle Gay-Ovéjéro Stéphane Rodrigues Jean-Paul Bakyono Lionel Visset |
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| Institution: | 1. Université François-Rabelais de Tours, CNRS/INSU, Université d’Orléans, UMR 6113 ISTO (Institut des Sciences de la Terre d''Orléans), Laboratoire de géologie, Avenue Monge, F-37200 Tours, France;2. Université de Nantes, UMR CNRS 6566, Laboratoire d’écologie et des paléoenvironnements atlantiques, Faculté des Sciences et des Techniques, 44322 Nantes, France;1. Université de Toulouse; INPT, UPS; EcoLab (Laboratoire écologie fonctionnelle et environnement), Ecole Nationale Supérieure Agronomique de Toulouse (ENSAT), Castanet Tolosan, France;2. CNRS; EcoLab (Laboratoire écologie fonctionnelle et environnement), Castanet Tolosan, France;1. Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster LA1 4YQ, UK;2. European Commission, Joint Research Centre, Institute for Environment and Sustainability, Via E. Fermi 2749, I-21027 Ispra, VA, Italy;3. Department of Electronics, Information, and Bioengineering, Politecnico di Milano, Piazza Leonardo da Vinci, 32, 20133 Milano, Italy;1. Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN, USA;2. Present Address: Graham Sustainability Institute, University of Michigan, Ann Arbor, MI, USA;3. Department of Earth Atmospheric and Planetary Sciences, Purdue University, West Lafayette, IN, USA;4. Department of Biology, Ball State University, Muncie, IN, USA;1. Department of Chemistry and Geochemistry, Montana Tech of The University of Montana, 1300 W. Park St., Butte, MT 59701, United States;2. Department of Geological Engineering, Montana Tech of The University of Montana, 1300 W. Park St., Butte, MT 59701, United States;1. Department of Biology and GeoBioTec – GeoBioSciences, GeoTechnologies and GeoEngineering Research Centre, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal;2. MARE-Marine and Environmental Sciences Centre, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3001-456 Coimbra, Portugal;3. Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Australia;4. MARE-Marine and Environmental Sciences Centre, Department of Civil Engineering, University of Coimbra, Rua Luís Reis Santos, 3030-788 Coimbra, Portugal |
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| Abstract: | The morpho-sedimentary evolution of the Choisille floodplain (lowland river, catchment: 288 km2), a tributary of the River Loire in the south-western Parisian Basin, was studied through 61 core drillings along eight transects and a geophysical survey located in four stretches of the river: stretches A and B correspond to two sub-catchments, and stretches C and D are in the main valley. Sixty 14C and four OSL datings were obtained, and sediments were analysed on seven reference cores. Eight phases of evolution differing markedly from the evolution of more northern areas in the Parisian Basin and north-western Europe were identified from spatio-temporal distribution of nine lithological facies. The deepest incision phase (1) occurred during the first part of the Weichselian, followed by the deposition of a gravelly-sandy unit (phase 2) during the Middle Pleniglacial, which was deeply incised (phase 3), probably during the Bölling. From the Allerød up to the last third of the Boreal (phase 4), sedimentation was continuously dominated by peaty deposits, with no evidence of either increased hydraulic energy during the Younger Dryas, or of incision during the LateGlacial–Holocene transition. This trend seems to reflect the specificity of the south-western Parisian Basin climate from the Late Weichselian up to the end of the Boreal, due to the influence of the Atlantic Ocean, compared to more northern areas where the climate was more continental. The downstream incision trend during the last third of the Boreal up to the Subatlantic (phases 5 and 6) indicates a sharp increase in precipitation and vegetation cover; the lack of peaty sediments, widespread in north-western Europe, and also of precipitated carbonates frequent in the Parisian Basin, seems to be due to local physiographic characteristics. The main part of the sediment filling, which is principally silty and retrograde, began during the Subatlantic (phase 7 and 8) as a result of deforestation of the plateaux for crop farming. High human-induced sediment yield and storage concealed the possible impacts of climate change on fluvial dynamics: lithological facies change from phase 7 to 8 can only indicate the autogenic morphological evolution of the floodplain in accretion. The non-univocal upstream–downstream variation in the start of phase 7 shows that sediment yield varied in space and time in the catchment, particularly in relation to the agricultural potential of the different areas; this observation could be used to testify human-induced sedimentation in other catchments. |
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