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August): Response of the Rhine-Meuse fluvial system to Saalian ice-sheet dynamics.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.

A revised Upper Cenozoic stratigraphic framework of the Dutch sector of the North Sea Basin is presented whereby offshore stratigraphic units are integrated or correlated with onshore units. The framework is based on an integrated stratigraphic approach that combines elements of lithostratigraphy, seismostratigraphy and allostratigraphy. Offshore formations are redefined in terms of seismofacies and lithofacies associations, and are differentiated on the basis of common genesis and stratigraphic position. These facies associations represent five major depositional environments, which occur in repetitive successions in the subsurface of the Netherlands: Marine, Coastal, Glacial, Fluvial, and Local Terrestrial.Five conceptual basin-wide bounding discontinuities are identified in the North Sea-Basin that span land and sea. They are represented by both seismostratigraphic and lithostratigraphic unconformities and interpreted as surfaces that formed as a result of North Sea Basin-wide changes in depositional systems. Their formation relates to sea level rise, continental-scale glaciations, and tectonic processes. The bounding discontinuities separate informal allostratigraphic groups of formations that have a grossly uniform geologic setting in common. While the allostratigraphic principles provide a view on the stratigraphy on the largest spatial and temporal scale, the genetic concept facilitates mapping on a local scale.

The landscape evolution of the southern North Sea basin is complex and has left a geographically varying record of marine, lacustrine, fluvial and glacial sedimentation and erosion. Quaternary climatic history, which importantly included glaciation, combined with tectonics gave rise to cyclic and non-cyclic changes of sedimentation and erosion patterns. Large-scale landscape reorganisations left strong imprints in the preserved record, and are important for the detail that palaeogeographical reconstructions for the North Sea area can achieve. In the spirit of the North Sea Prehistory Sea. It summarises current stratigraphical and chronological frameworks and provides an overview of sedimentary environments. As we go back in time, the understanding of Quaternary palaeo-environmental evolution in the North Sea basin during the last 1 million years becomes decreasingly accurate, with degree of preservation and accuracy of age control equally important controls. Comparing palaeogeographical reconstructions for the Middle Pleistocene, the last interglacial-glacial cycle and the period following the Last Glacial Maximum illustrates this. More importantly, a series of palaeogeographical maps provide an account of basin-scale landscape change, which provides an overall framework for comparing landscape situations through time.

Eight continuous corings in the west-central Netherlands show a 15 to 25 m thick stacked sequence of sandy to gravelly channel-belt deposits of the Rhine-Meuse system. This succession of fluvial sediments was deposited under net subsiding conditions in the southern part of the North Sea Basin and documents the response of the Rhine-Meuse river system to climate and sea-level change and to the glaciation history. On the basis of grain size characteristics, sedimentological structures, nature and extent of bounding surfaces and palaeo-ecological data, the sequence was subdivided into five fluvial units, an estuarine and an aeolian unit. Optical dating of 34 quartz samples showed that the units have intra Saalian to Weichselian ages (Marine Isotope Stages 8 to 2). Coarse-grained fluvial sediments primarily deposited under cold climatic conditions, with low vegetation cover and continuous permafrost. Finer-grained sediments generally deposited during more temperate climatic conditions with continuous vegetation cover and/or periods of sea-level highstand. Most of the sedimentary units are bounded by unconformities that represent erosion during periods of climate instability, sea-level fall and/or glacio-isostatic uplift.

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The Hennisdijk fluvial system in the central Rhine‐Meuse delta is an abandoned Rhine distributary that was active on a wide floodplain from 3800 to 3000 years BP. Cross‐sectional geometry, lithological characteristics and planform patterns of the channel‐belt deposits indicate lateral migration of the Hennisdijk palaeochannel. Channel‐belt deposits are around 10 m thick and 200–400 m wide. A gravelly facies near the base of the channel‐belt deposits represents channel‐lag and lower point‐bar deposits. The axis of the channel belt is dominated by a sandy facies (medium and coarse sand), showing an overall fining upward trend with multiple cycles. This facies is interpreted as lower and middle point‐bar deposits. The sandy facies is capped by a muddy facies, which is 1–2 m thick near the axis of the channel belt and thickens to 5–6 m along the margins. It laterally interfingers with the sandy facies that occurs near the channel‐belt axis, but it has sharp, erosive outer contacts marking the edges of the channel belt. The muddy facies comprises inclined heterolithic stratification (IHS) (fine/medium sand–mud couplets) in its upper part. The relatively thin muddy facies with IHS that occurs near the channel‐belt axis is interpreted as upper point‐bar deposits with lateral accretion surfaces, formed under marine influence. Along the margins of the channel belt the muddy facies consists of thick, fairly homogeneous, successions of mud with variable sand content, and fine sand. Based on facies geometry and position, this part of the muddy facies is interpreted as counterpoint deposits, formed along the upstream limb of the concave bank of a channel bend. Counterpoint accretion seems to have been associated with the confined nature of the channel belt, which was the result of low stream power (4·5–7·8 W m−2, based on reconstructions of palaeodischarge and channel slope) and cohesive bank material, i.e. clayey floodbasin deposits with intercalated peat beds occurring next to the channel belt. In the literature, counterpoint accretion is mostly reported from alluvial valleys, where meandering is confined by limited floodplain width, whereas muddy lateral accretion surfaces are commonly reported from much wider marine‐influenced floodplains. The present study shows juxtaposition of both forms of muddy channel deposits in a low‐energy, wide coastal plain setting, where preservation potential is considerable.

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