Texture and sedimentation rates in Lake Geneva |
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| Authors: | J -P Vernet J Dominik P Y Favarger |
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| Institution: | (1) Institut F.-A. Forel, Université de Genève, 1290 Versoix, Switzerland |
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| Abstract: | Thirty two cores were collected from Lake Geneva sediments along one longitudinal and eight transverse profiles. Rates of sedimentation determined by137Cs vary from 0.01 to 1.86 g cm?2 y?1. The average deposition rates in coastal and slope areas amounts to 0.37 g cm?2 y?1 in the Upper Lake (Grand Lac) and 0.12 g cm?2 y?1 in the Lower Lake (Petit Lac). In the deep basins, average rates of 0.13 and 0.05 g cm?2 y?1 were found for the Grand Lac and Petit Lac, respectively. The estimated mass of sediment deposited yearly outside of the principal deltas and turbidity current depositional areas is about 1.0 million tons (about 13% of the estimated total river load). One turbidite is clearly identified in the deepest, central lake area. There is little variation of surface sediment texture (mean grain size about 8–9µm) with the exception of delta areas. Since the beginning of the twentieth century, both carbonate and organic matter have increased as a result of lake eutrophication. |
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