Abstract

At present, little evidence is available on avulsion rates, avulsion frequencies, and interavulsion periods of aggrading fluvial systems over time scales of millenia. The large number of high-quality 14C ages from the Holocene Rhine-Meuse delta (central Netherlands) enables a detailed assessment of such avulsion parameters and an evaluation of the factors controlling avulsion frequency. 14C histogram analysis indicates that instantaneous avulsion (coexistence of successive channel belts for less than a few centuries) has dominated in this area. Interavulsion 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 characterized by large-scale transgressive tendencies. The time interval with the largest number of coexisting distributaries corresponds to the period with dominance of anastomosing fluvial style.

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