Late Weichselian and Holocene ftuvial palaeogeography of the southern Rhine-Meuse delta (the Netherlands)

Abstract

During the Late Weichselian, climatic changes induced the formation of a two-fold terraced braided-river plain that was formed by precursors of the rivers Rhine and Meuse in the central Netherlands. The older (and higher) terrace is Pleniglacial. It is partly covered by river dunes and coversand of Younger Dryas age. The younger (and lower) terrace originated during the Younger Dryas. Sealevel rise during the Holocene forced the rivers to aggrade since the Early Atlantic. Since then, avulsions have led to a complicated palaeo-channel pattern in which Rhine and Meuse precursors still can be distinguished. River avulsions occurred predominantly during three periods; between 5000 and 4000 BP, around 3000 BP, and around 1800 BP. These periods ofincreased avulsion frequency have also been found in the northern and central parts of the delta. Rivers were essentially meandering, but in the western part of the area anastomosing rivers existed before 3000-4000 BP. Some Meuse distributaries also have an anastomosing pattern around circa 2000 BP, although they show lateral accretion, and have a rather high width/thickness ratio (40-60). Meander wavelength increased considerably in the Middle Ages. This reflects an increase in peak discharge.