SEDIMENT YIELD FROM GLACIO-LACUSTRINE CALCAREOUS DEPOSITS DURING THE POSTGLACIAL PERIOD IN THE COMBE DAIN (JURA, FRANCE)

The middle valley of the river Ain (Jura) cuts through glacio-lacustri ne deposits laid down in an ice-damned lake during the most recent gla cial advance. The total volume eroded is about 6.21x10(8) m(3) for a s urface area of 3.7x10(7) m(2). Erosion occurred between 18ka BP and 6k a BP, i.e. over a duration of some 12ka. Sediment yield from the area was of the order of 2500 km(-2) a(-1), which is comparable with modem- day sediment yield from NW African badlands. These high values are asc ribed to the amenability of glacio-lacustrine deposits to mechanical w eathering and to the rapid geomorphological changes that affected glac ial and paraglacial sedimentary cover after the retreat of the ice. Th e valley slopes were destabilized by mass wasting (earthflow and mudfl ow), which was the predominant erosional process. The slopes are curre ntly stabilized or very exceptionally active. (C) 1998 John Wiley & So ns, Ltd.