A TRANSITION FROM A BRAIDED TO A MEANDERING CHANNEL FACIES, SHOWING INCLINED HETEROLITHIC STRATIFICATION (LATE WEICHSELIAN, CENTRAL NETHERLANDS)

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 (facie s 2) was formed by a small-scale channel and is characterized by claye y lateral accretion surfaces, indicated by inclined heterolithic strat ification (IHS). This point bar sequence has features indicative of va riable discharge during deposition during a transitional stage from a braided to a meandering channel pattern. The younger point bar sequenc e (facies 3) was formed by a larger channel that incised the braidplai n and is thought to represent a fully developed meandering channel pat tern. IHS was not found in these deposits. Point bar formation at the study location ceased during the Allerod or early Younger Dryas when t he meandering channel was abandoned. The fill of this residual channel (facies 4) consists of gyttja, pear and (humic) clay. Finally, the po int bars and the residual channel were covered by floodbasin deposits of Holocene meandering river systems (also facies 4) which consist pre dominantly of clay.