ARCHITECTURE OF A PRESERVED HOLOCENE TIDAL COMPLEXOFFSHORE THE RHINE-MEUSE RIVER MOUTH, THE NETHERLANDS

摘要

Integration of existing and newly collected geological, geotechnical, andrngeophysical data from the Rhine-Meuse river mouth has increased our knowledge on thernstratigraphy and development of this coastal area. This new, detailed knowledge isrnnecessary to gain insight into the relationship between river-mouth behavior and changesrnin the river systems feeding the associated estuary with water and sediment, and tornunderstand the interaction between the river mouth and the adjacent barrier coast. In thernstudy area, Pleistocene facies are covered and locally incised by the deposits of a complexrnestuarine system composed of tidal flats and increasingly mobile tidal channels. Thernestuary came into existence during a phase of regional coastline retrogradation, governedrnby rapid sea-level rise, and probably formed a promontory extending into the North Sea.rnDuring the Subboreal, much of the estuarine promontory was eroded, and it was not untilrnthe Subatlantic that this erosion-dominated phase ended. The ensuing sedimentation phasernprobably culminated during the Medieval period. These phases appear to be related tornchanges in the upland river systems. At the end of the Atlantic, an avulsion resulted inrncapturing of much of the water and sediment entering the North Sea near the presentrnRhine-Meuse estuary by a more northerly system. In the early Subatlantic, anotherrnavulsion resulted in deterioration of this northerly system and in the development of a newrnsoutherly system, stimulating progradation of the by then degraded Rhine-Meuse estuary.rnConceivably, much of the sediment eroded in the river-mouth area during the Atlantic wasrntrapped in the large tidal basins present in the western Netherlands at that time. Once theserntidal basins had filled up, and tidal inlets closed, the increasing sediment surplus (from allrnsources) could be used for barrier progradation in the Subboreal. Thus, it is likely thatrnreworking of the Atlantic river-mouth sediment has expedited the transition from arnretrograding to a prograding coastline.