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7200 years of Rhône river flooding activity in Lake Le Bourget, France: a high-resolution sediment record of NW Alps hydrologyUMR 8110 Processus et Bilan en Domaine Sedimentairé, UST Lille 1 Bât. SN5 59655 Villeneuve d'Ascq, France; UMR 5025 Laboratoire de Géodynamique des Chaines Alpines, Universite de Savoie, 73373 Le Bourget du Lac, France fabien.arnaud{at}univ-savoie.fr
UMR 5025 Laboratoire de Géodynamique des Chaînes Alpines, Observatoire des Sciences de l'Univers de Grenoble, Université J. Fourier, 38400 St Martin d'Hères, France
UMR 6113 Institut des Sciences de la Terre d'Orléans, Université d'Orléans, 45071 Orléans, France; Geological institute, ETH Zurich, Switzerland
UMR 5025 Laboratoire de Geodynamique des Chaines Alpines, Université de Savoie, 73373 Le Bourget du Lac, France
UMR 8110 Processus et Bilan en Domaine Sédimentaire, UST Lille 1 Bât. SN5 59655 Villeneuve d'Ascq, France Magnetic susceptibility (MS) was measured with high resolution (5 mm) on a 9 m long, 14C dated core from Lake Le Bourget (Savoie, France), spanning the last 7200 years. The strong correlation (R=0.85) of the MS with the silicate-borne suite of elements (Si, Al, Fe, Mg, K) and anti-correlation with the carbonate content (R =-0.87) allows it to be used as a proxy for the fluctuations of the abundance of riverborne clastic fraction versus authigenic carbonates in sediment. As the Rhône is the only river bringing a significant amount of silicate minerals to the coring site, the MS downstream is interpreted as a proxy of the Rhône suspended load discharge in Lake Le Bourget. This is confirmed over the last 3000 years by the good match with the evolution of hydrological activity of the Rhône as it is known through geomorphological studies of well-dated archaeological sites. Over the last 7200 years, the record is consistent with the regional record of lake water-level fluctuations. While the intensity of the MS signal might be widely affected by the human impact on soil stability, the timing of the period of enhanced hydrological activity appears to be mostly climate-related, and should thus constitute a first step toward a high-resolution (< 8 yr) continuous history of hydrological conditions in the NW Alps.
Key Words: River discharge floods palaeohydrology climate human impact magnetic susceptibility silicate minerals major elements Rhône Alps France Holocene
The Holocene, Vol. 15, No. 3,
420-428 (2005) This article has been cited by other articles:
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