Response of the Rhine–Meuse fluvial system to Saalian ice-sheet dynamics FREEK S. BUSSCHERS, RONALD T. VAN BALEN, KIM M. COHEN, CEES KASSE, HENK J. T. WEERTS, JAKOB WALLINGA AND FRANS P. M. BUNNIK BOREAS Busschers, F. S., van Balen, R. T., Cohen, K. M., Kasse, C., Weerts, H. J. T., Wallinga, J. & Bunnik, F. P. M. 2008 (August): Response of the Rhine–Meuse fluvial system to Saalian ice-sheet dynamics. Boreas, Vol. 37, pp. 377–398. 10.1111/j.1502-3885.2008.00025.x. ISSN 0300-9483. A new reconstruction of the interaction between the Saalian Drente glaciation ice margin and the Rhine–Meuse fluvial system is presented based on a sedimentary analysis of continuous core material, archived data and a section in an ice-pushed ridge. Optically Stimulated Luminescence (OSL) was applied to obtain independent age control on these sediments and to establish a first absolute chronology for palaeogeographical events prior to and during the glaciation. We identified several Rhine and Meuse river courses that were active before the Drente glaciation (MIS 11-7). The Drente glaciation ice advance into The Netherlands (OSL-dated to fall within MIS 6) led to major re-arrangement of this drainage network. The invading ice sheet overrode existing fluvial morphology and forced the Rhine–Meuse system into a proglacial position. During deglaciation, the Rhine shifted into a basin in the formerly glaciated area, while the Meuse remained south of the former ice limit, a configuration that persisted throughout most of the Eemian and Weichselian periods. An enigmatic high position of proglacial fluvial units and their subsequent dissection during deglaciation by the Meuse may partially be explained by glacio-isostatic rebound of the area, but primarily reflects a phase of high base level related to a temporary proglacial lake in the southern North Sea area, with lake levels approximating modern sea levels. Our reconstruction indicates that full ‘opening’ of the Dover Strait and lowering of the Southern Bight, enabling interglacial marine exchange between the English Channel and the North Sea, is to be attributed to events during the end of MIS 6. Freek S. Busschers (e-mail: freek.busschers@tno.nl), Department of Paleoclimatology and Geomorphology, Faculty of Earth and Life Sciences, Vrije Universiteit, The Netherlands (present address: TNO Built Environment and Geos- ciences Geological Survey of The Netherlands, Utrecht, The Netherlands); Ronald T. van Balen and Cees Kasse, Department of Paleoclimatology and Geomorphology, Faculty of Earth and Life Sciences, Vrije Universiteit, The Netherlands; Kim M. Cohen, Department of Physical Geography, Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands; Henk J. T. Weerts, TNO Built Environment and Geosciences Geological Survey of The Netherlands, Utrecht, The Netherlands; Jakob Wallinga, Netherlands Centre for Luminescence Dating (NCL), Delft University of Technology, Faculty of Applied Sciences, Delft, The Netherlands; Frans P. M. Bunnik, TNO Built Environment and Geosciences Geological Survey of The Netherlands, Utrecht, The Netherlands; received 14th July 2007, accepted 18th December 2007. The Drente ice-sheet expansion left a strong imprint on the morphology of the southern North Sea Basin area in northwest Europe. Glaciotectonic ridges, deeply scoured basins, sandur plains and till sheets are mor- phological evidence of one or more ice-sheet advances, of which the Drente glaciation is regarded as being the primary event (Zagwijn 1973). The invading ice sheet caused a re-organization of drainage networks, notably the lower valley of the Rhine, and its glacially imposed morphology remained an important control on the drainage configurations in the Late Pleistocene. In The Netherlands and Germany, the sedimentary and mor- phological products of the Saalian glaciation have been the topic of numerous studies (van den Berg & Beets 1987; Meyer 1987; Kluiving et al. 1991; Laban 1995; Skupin et al. 1993, 2003; Van der Wateren 1995; Ehlers et al. 2004; Bakker & van der Meer 2003) (Fig. 1), most dealing with till provenance, till fabric, the internal structure of ice-pushed ridges and glacial morphology (e.g. eskers, tunnel valleys, drumlinized ridges and megaflutes). Less attention has been given to drainage pattern changes in relation to the ice-sheet dynamics. The Saalian history of the Rhine, the most south- western Scandinavian ice-sheet ice-marginal river, has been addressed by several authors in local and regional overview studies (e.g. Thome´ 1959; Verbraeck 1984; van den Berg & Beets 1987; Klostermann 1992). How- ever, an integrated sedimentary analysis of the interac- tion between the Rhine–Meuse river system and the ice margin, as well as independent absolute chronological control for these sediments, is missing, a feature that is in strong contrast to the Late Pleistocene Rhine evolu- tion (Van de Meene & Zagwijn 1978; Verbraeck 1984; Busschers et al. 2007). In this article, we provide a reconstruction of the in- teraction between the ice margin and the Rhine–Meuse river system in The Netherlands based on sedimentary analysis of new continuous core material, a national borehole database and a section in an ice-pushed ridge. We applied Optically Stimulated Luminescence (OSL) dating to sand-sized quartz grains to obtain in- dependent age control on the sediments and palaeo- geographic events that occurred prior to and during the glacial phase. We discuss the imprints of proglacial lake development and glacio-isostasy on the Rhine–Meuse architecture preserved from the Saalian, and highlight DOI 10.1111/j.1502-3885.2008.00025.x r 2008 The Authors, Journal compilation r 2008 The Boreas Collegium