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Major sedimentation pattern changes in the Rhone Delta (Lake Geneva, Switzerland-France) around 1300 and 1600 AD revealed by seismic and sedimentary records

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Published in Archives des Sciences. 2010, vol. 64, p. 9-20
Abstract The seismic record of recent sediments of the Rhone delta in Lake Geneva (Switzerland, France) presents a discontinuity over a large area of the delta. Previous studies hypothesized that sediments inducing this discontinuity could originate from a giant rock fall (named Tauredunum) that occurred in the Lake Geneva watershed in 583 AD. To verify this hypothesis, two long cores have been retrieved from the lake sediments in the region where the sediment pile thickness is reduced. The sediment sequence presented three major units, with an upper, fine grained and laminated sediments (Unit A), and intermediate unit consisting of alternating coarse and fine grained sediments (Unit B), and a lower unit (Unit C) with sediment characteristics comparable to Unit (A). Unit B was interpreted as sediments inducing the seismic discontinuity. Two organic remains were sampled in Unit B and Unit A, and dated by AMS 14C to 1390-1440 cal. AD and 1680-1780 cal. AD, respectively. The base of Unit B was dated by extrapolation to 1310 cal. AD that is more than six centuries after the Tauredunum rock fall. Moreover, the structure of the intermediate unit was interpreted as a succession of turbidite deposits and hemipelagic sedimentation. The mode of deposition of the sediments and, mainly, the AMS 14C dating of organic remains invalidate the hypothesis of an origin of the intermediate unit in relation to the Tauredunum rock fall. Possible processes are larger inputs (as compared to present time) of detrital material during the “Little Ice Age” and a shift in the sand lobes at the end of sub-lacustrine canyons.
Keywords Radiocarbon datingLémanTauredunumSeismic reflectionLake sediment
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Structures
Research groups Limnology and Environmental Geology
ISE Pôle Sciences
ISE Eau
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LOIZEAU, Jean-Luc. Major sedimentation pattern changes in the Rhone Delta (Lake Geneva, Switzerland-France) around 1300 and 1600 AD revealed by seismic and sedimentary records. In: Archives des Sciences, 2010, vol. 64, p. 9-20. https://archive-ouverte.unige.ch/unige:27146

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Deposited on : 2013-04-03

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