Alluvial architecture of the Quaternary Rhine-Meuse river system in the Netherlands

Abstract

In the Rhine-Meuse river system in the Netherlands, a combination of major tectonic movements and climatic cycles (periglacial to temperate-warm, non-arid) has resulted in different sedimentation patterns on either side of the terrace intersection. Upstream of this intersection, a vertical series of river terraces was formed by the alternating processes of erosion of the valley by meandering river action and partial refilling of the valley by braided river action. The coarse-grained gravelly deposits within these terrace units show the characteristics of a braided river(Scott-type sequentional model) and reflect general aggradation during cold, i.e. glacial, stages. During interglacials, meandering rivers cut into the previously formed braided river deposits causing net sediment removal. Deposits dating from interglacials are very scarce. Downstream of the intersection, the average sedimentation rate kept up with subsidence. Sediment was supplied mostly by braided rivers during cold stages and the resulting sequences resemble the Donjek-type sequentional model. During interglacial times meandering rivers mainly caused reworking and erosion of braided river deposits from the preceding glacial stage. Meandering river deposits are more widespread than upstream of the intersection; they are interbedded between braided river deposits. Futher downstream, marine transgressions during interglacials caused the coast-related anastomosing river zone to shift upstream, sometimes as far as the present-day western Netherlands. As a consequence of the mechanism responsible for forming fluvial terraces upstream of the terrace intersection, fine-grained overbank and cut-off sediments from meandering rivers that potentially can be dated palaeontologically may be expected underneath coarse-grained 'river-terrace' deposits.