High-resolution seismic stratigraphy of glacial to interglacial fill of a deep glacigenic lake: Lake Le Bourget, Northwestern Alps, France

Lake Le Bourget is a deep, peri-alpine glacial lake originating from the last glacial, the Wurm, The lake has amassed over 250 m of sediment since the Last Glacial Maximum. Two seismic sparker surveys on the lake revealed the glacial and post-glacial sedimentary infill, the depth and the morphology of the Wurm erosion Surface and penetrated the Riss-Wurm interglacial deposits as deep as the underlying Riss erosion surface. The density of the seismic grid and the high resolution of the data, even at greater depths, allowed a detailed study of the sedimentary processes and of their evolution throughout the deglaciation. Five main seismic facies characterise the basin fill. They are interpreted as glacial deposits, glacio-lacustrine sediments, proglacial lacustrine fans, alluvial fan deltas and authigenic lacustrine drape. These occur as a suite of deposits associated with the major lake tributaries and are the result of major changes in sediment supply and style of discharge into the lake. The three-dimensional facies associations within the basin fill document the history of the basin and its catchment area since the onset of the deglaciation. (C) 1999 Elsevier Science B.V. All rights reserved.