The Late Pleistocene aeolian system of the Rhône Valley (southeast France).
For almost a century, thick Pleistocene aeolian deposits have been recognised in the southern branch of the Western European Cenozoic Rift, i.e. the lower Rhone Valley and the valleys of the Alpine tributaries. The loess, disconnected from the two main European aeolian systems (the North European Lo...
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| Other Authors: | , , , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | French |
| Published: |
HAL CCSD
2020
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| Subjects: | |
| Online Access: | https://tel.archives-ouvertes.fr/tel-03245701 https://tel.archives-ouvertes.fr/tel-03245701/document https://tel.archives-ouvertes.fr/tel-03245701/file/BOSQ_MATHIEU_2020.pdf |
| Summary: | For almost a century, thick Pleistocene aeolian deposits have been recognised in the southern branch of the Western European Cenozoic Rift, i.e. the lower Rhone Valley and the valleys of the Alpine tributaries. The loess, disconnected from the two main European aeolian systems (the North European Loess Belt and the Danube basin), constitute a key record for documenting the evolution of the peri-Mediterranean glacial palaeoenvironments. Loess is characterized by a coarse texture (main mode around 60 μm), polymodal grain-size distribution, strong local thickness (>5 m), limited extension, high carbonate content and abundant bioturbation. This results from the persistence of a shrub vegetal cover during the coldest and driest phases of the Last Glacial that allowed for trapping the saltating and suspended particles close to the alluvial sources. At the European scale, the geochemical composition of loess changes according to regions, but remains consistent within each catchment. Such variability is mostly related to the composition of rocks outcropping in glaciated areas within the respective catchments. A sedimentological and chronostratigraphic investigation was carried out on two loess-palaeosols sections: the Collias section (~8 m thick), which records the whole last climatic cycle, and the Lautagne section (4 m thick), which provides a detailed record of the Upper Pleniglacial. At a regional scale, the time of loess deposition ranges from 37.5 ka to 12 ka, with a peak at ~28–24 ka, overlapping the maximal advance of the Alpine Ice Sheet. This strongly suggests that regional glacier dynamics was the main driver of loess sedimentation by modulating the production of particles likely to be transported by deflation. Depuis presque un siècle, d’importants dépôts éoliens pléistocènes ont été reconnus dans la branche méridionale du rift cénozoïque ouest-européen, i.e. la basse vallée du Rhône et celles de ses affluents alpins. Ces lœss, déconnectés des deux principaux systèmes éoliens européens (la ceinture ... |
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