A transition from a braided to a meandering channel fades, showing inclined heterolithic stratification (Late Weichselian, central Netherlands)

Abstract

An excavation near Deest (Land van Maas en Waal, central Netherlands) offered an opportunity to study sedimentary structures near the top of the Late Weichselian Kreftenheye Formation in two point bar sequences showing different lithofacies. The sandy point bars rest on gravelly braided river deposits (facies 1). The older point bar sequence (facies 2) was formed by a small-scale channel and is characterized by clayey lateral accretion surfaces, indicated by inclined heterolithic stratification (IHS). This point bar sequence has features indicative of variable discharge during deposition during a transitional stage from a braided to a meandering channel pattern. The younger point bar sequence (facies 3) was formed by a larger channel that incised the braidplain and is thought to represent a fully developed meandering channel pattern. IHS was not found in these deposits. Point bar formation at the study location ceased during the Allerød or early Younger Dryas when the meandering channel was abandoned. The fill of this residual channel (facies 4) consists of gyttja, peat and (humic) clay. Finally, the point bars and the residual channel were covered by floodbasin deposits of Holocene meandering river systems (also facies 4) which consist predominantly of clay.