MIDDLE AND LATE HOLOCENE AVULSION HISTORY OF THE RIVER RHINE (RHINE-MEUSE DELTA, NETHERLANDS)

At present, little evidence is available on avulsion rates, avulsion f requencies, and interavulsion periods of aggrading fluvial systems ove r time scales of millenia. The large number of high-quality C-14 ages from the Holocene Rhine-Meuse delta (central Netherlands) enables a de tailed assessment of such avulsion parameters and an evaluation of the factors controlling avulsion frequency. C-14 histogram analysis indic ates that instantaneous avulsion (coexistence of successive channel be lts for less than a few centuries) has dominated in this area. Interav ulsion periods were typically 1000 yr, although values of 500 or 5000 yr have also been found. Avulsion frequency was especially large prior to 4300 cal. yr B.P., indicating a strong control by aggradation rate , in turn controlled by sea-level rise. In addition, periods with high avulsion frequency appear to correlate with time intervals characteri zed by large-scale transgressive tendencies. The time interval with th e largest number of coexisting distributaries corresponds to the perio d with dominance of anastomosing fluvial style.