Modeling longitudinal-profile development in response to Late Quaternary tectonics, climate and sea-level changes: the River Meuse

We present a forward-modelling case study for the development of the longit udinal profile of a basin-marginal fluvial system (River Meuse, NW Europe) responding to Late Quaternary tectonics, climate and sea-level changes. Modelling results show that river reaches in different tectonic domains wil l respond differently to isochronous events of climate and sea-level change . Climatic change dominates river-valley development in the long-term uplif ting upper and middle Meuse reaches (NE Paris Basin, Ardennes, terrace flig ht area). An alternation of stadial depositional and interstadial erosional phases causes net aggradation of the river valley during glacials, but the river valley considerably degrades during interglacials. The long-term tre nd in these upper and middle reaches is river-valley degradation. Continuous aggradation leads to long-term deposition during glacials in the subsiding lower Meuse reaches, including the greater part of the Venlo-Blo ck area, the western Roer Valley Graben and the southern part of the West N etherlands Basin. However, decreasing sediment supply combined with increas ing discharges at the start of interglacials favours discharge controlled ( kinetic) incision in these net-depositional areas. Post-glacial sea-level r ise and the subsequent interglacial highstand strongly influence the subsid ing graben areas and the southern West Netherlands Basin. Rising sea level generates a zone of gradient-backfilling that migrates upstream with time. Consequently, the terrace intersection migrates upstream too and a coastal prism is built up during the interglacial highstand. The present case study indicates that the Meuse terrace intersection may migrate to at least 113 km upstream from the modelled coastline. The model also suggests post-inter glacial incision of the Eemian highstand coastal prism during the subsequen t relative sea-level fall in the Early Weichselian. (C) 2000 Elsevier Scien ce B.V. All rights reserved.