AN EXAMPLE OF SOFT-SEDIMENT DEFORMATIONS IN AN INTERTIDAL ENVIRONMENT - THE EFFECT OF A TIDAL BORE

Some soft sediment deformations, reaching 40 cm in amplitude, have been observed along a tidal channel in the internal estuarine area of the Mont-Saint-Michel Bay (NW France). These deformations which involve a silt dominated detrital sediment, display two main shape types: folds and ''tobacco-pouches''. The character of the channel, the location of these deformations, the gradual changes in their shape and amplitude, and the orientation of the fold axis are arguments to attribute these structures to liquefaction, and subsequent deformation of non-consolidated sediments by the passage of a tidal bore.