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Quaternary Science Reviews 29, 17-18 (2010) 2185-2200
North western Alps Holocene paleohydrology recorded by flooding activity in Lake Le Bourget, France and possible relations with Mont-Blanc glaciers fluctuations
Maxime Debret 1, Emmanuel Chapron 1, Marc Desmet 1, M. Rolland-Revel 2, O. Magand 3, Alain Trentesaux 4, Viviane Bout-Roumazeilles 4, Jérôme Nomade 5, Fabien Arnaud 6

A 14-m long piston core was retrieved from Lake Le Bourget, NWAlps (France), in order to provide a continuous record of flooding events of the Rhone River during the Holocene. The selection of the coring site was based on high resolution seismic profiling, in an area with limited mass wasting deposits and accumulated proximal Rhone River inter-and underflow deposits. The age-depth model of this core is based on (i) 14 AMS radiocarbon dates, (ii)radionuclide dating(137Cs) and (iii) the identification of historical data (flood events, eutrophication of the lake).The sedimentary record dates back to 9400 cal BP, and includes a thin mass wasting event deposited around 4500 cal BP. A multi-proxy approach was used to track the evolution and origin of clastic sedimentation during the Holocene, in order to identify periods of higher hydrologic al activity in the catchment area. Spectrophotometry was used to detect fluctuations in clastic supply and the study of clay minerals (especially the Illite crystallinity index) allowed locating the main source area of fine grained clastic particles settling at the lake after flood events. This dataset highlights up to 12 periods of more intense flooding events over the last 9400 years in Lake Le Bourget and shows that the main source area of clastic particles during this period is the upper part of the Arve River drainage basin. This part of the catchment area drains several large glaciers from the Mont-Blanc Massif, and fluctuations in Rhone River flood supply in Lake Le Bourget is interpreted as resulting essentially from Mont-Blanc Glacier activity during the Holocene.The comparison of clastic sedimentationin Lake Le Bourget with periods of increasing land use and periods of Alpine glacier and mid-European lake level fluctuations, suggest that the core LDB04 clastic record in Lake Le Bourget is a continuous proxy of the Holocene hydrologic al history of the NW Alps.
1 :  Institut des Sciences de la Terre d'Orléans (ISTO)
CNRS : UMR6113 – INSU – Université d'Orléans – Université François Rabelais - Tours
2 :  Géoazur (GEOAZUR)
Université Nice Sophia Antipolis (UNS) – CNRS : UMR7329 – Institut de recherche pour le développement [IRD] – Observatoire de la Côte d'Azur – INSU – Université Pierre et Marie Curie (UPMC) - Paris VI
3 :  Laboratoire de glaciologie et géophysique de l'environnement (LGGE)
CNRS : UMR5183 – OSUG – INSU – Université Joseph Fourier - Grenoble I
4 :  Processus et bilan des domaines sédimentaires (PBDS)
CNRS : UMR8110 – INSU – Université Lille I - Sciences et technologies
5 :  Laboratoire de géodynamique des chaines alpines (LGCA)
CNRS : UMR5025 – OSUG – INSU – Université de Savoie – Université Joseph Fourier - Grenoble I
6 :  Environnements, Dynamiques et Territoires de la Montagne (EDYTEM)
CNRS : UMR5204 – Université de Savoie
Sciences de l'environnement/Milieux et Changements globaux
Holocene – Flooding events – Lake sediment – Alps – Detritism – Glacier fluctuations
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