Sediment yield from glacio-lacustrine calcareous deposits during the postglacial period in the Combe d’Ain (Jura,France)

The middle valley of the river Ain (Jura) cuts through glacio-lacustrine deposits laid down in an ice-dammed lake during the most recent glacial advance. The total volume eroded is about 6·21 × 10⁸ m³for a surface area of 3·7 × 10⁷ m². Erosion occurred between 18 ka BP and 6 ka BP , i.e. over a duration of some 12 ka. Sediment yield from the area was of the order of 2500 t km^?2 a^?1, which is comparable with modern-day sediment yield from NW African badlands. These high values are ascribed to the amenability of glacio-lacustrine deposits to mechanical weathering and to the rapid geomorphological changes that affected glacial and paraglacial sedimentary cover after the retreat of the ice. The valley slopes were destabilized by mass wasting (earthflow and mudflow), which was the predominant erosional process. The slopes are currently stabilized or very exceptionally active. © 1998 John Wiley & Sons, Ltd.