Architecture of the Holocene Rhine-Meuse delta (the Netherlands) - A result of changing external controls

Abstract

The Holocene Rhine-Meuse delta is formed under the influence of sea-level rise, tectonics, and variations in discharge and sediment supply. This paper aims to determine the relative importance of these external controls to improve our understanding of the evolution of the Rhine-Meuse fluvio-deltaic system. To do this, the geological and lithological composition of the fluvio-deltaic wedge has to be known in detail, both in space and time. This study presents five cross-valley sections in the Holocene Rhine-Meuse delta, based on almost 2000 shallow borings. Over 130 14C dates provide detailed time control and are used to draw time lines in the sections. Distinct spatio-temporal trends in the composition of the Holocene fluvio-deltaic wedge were found. In the upstream delta, the Holocene succession is characterised by stacked channel belts encased in clastic flood basin deposits through which several palaeo-A-horizon levels are traceable. In a downstream direction, the fluvio-deltaic wedge thickens from 3 to 7 m. The Holocene succession in the downstream cross sections formed from <8000 cal yr BP onwards and is characterised by single channel belts encased in organic flood basin deposits. The main part of the organic beds accumulated between 6000 and 3000 cal yr BP. After 3000 cal yr BP, clastic deposition dominated throughout the delta, indicating an increase in the area of clastic sedimentation. The Holocene fluvio-deltaic wedge is subdivided into three segments based on the relative importance of eustatic sea-level rise, subsidence, and upstream controls (discharge and sediment supply). Before 5000 cal yr BP, eustatic sea-level rise controlled the build-up of the wedge. After eustatic sea-level rise ceased, subsidence was dominant from 5000 to 3000 cal yr BP. From 3000 cal yr BP onwards, increased sediment supply and discharge from the hinterland controlled the formation of the fluvio-deltaic wedge. A significant part of the present-day Rhine-Meuse fluvio-deltaic wedge aggraded after eustatic sea-level rise ceased. We therefore conclude that external controls other than eustatic sea-level rise were also of major importance for the formation of the fluvio-deltaic wedge. Because this is probably true for other aggrading fluvial systems at continental margins as well, all external controls should be addressed to when interpreting (ancient) fluvio-deltaic successions.

North Sea palaeogeographical reconstructions for the last 1 Ma

“…All rivers in the North Sea area have been strongly affected by Holocene sea-level rise. It changed patterns of fluvial sedimentation up to c. 150 km from the coast in the low-gradient bigger rivers, played a role in the formation and demise of distributaries (and thus sediment delivery to the coast; Beets & van de Spek, 2000;Berendsen & Stouthamer, 2000;Hijma & Cohen, 2012), and governed peat formation in active and abandoned alluvial plains (and thus accommodation and preservation of palaeosurfaces and sedimentary layers including any contained archaeology and palaeoenvironmental information; Cohen, 2005;Gouw & Erkens, 2007). This also took place in earlier interglacials (e.g.…”

Potential of Holocene deltaic sequences for subsidence due to peat compaction

“…Berendsen and Stouthamer, 2001;Cohen, 2003;Gouw and Erkens, 2007;Gouw, 2008;Bos, 2010;Stouthamer et al, 2011). These studies allow to distinguish key clastic-organic sequences (Fig.…”

The age and origin of the Gelderse IJssel

“…Climatically induced stepwise incision and associated terrace formation (e.g. Berendsen et al, 1995) continued in the lower Rhine and Meuse valleys in the Late-Weichselian and Early-Holocene periods, ultimately leading to relatively narrow incised channel belts with surface levels below wide abandoned Weichselian terraces (Cohen, 2003;Gouw & Erkens, 2007) .…”

“…Approximately 4000 BP the upstream limit of onlap of Holocene deposits on Weichselian terraces had reached the area near Arnhem and Westervoort (Gouw & Erkens, 2007) (Fig. 1).…”

“…Moreover, in the whole Rhine-Meuse delta clastic sedimentation increased after 2000 BP and peat formation came to an end (Pons, 1957;De Boer & Pons, 1960;Berendsen, 1990;Berendsen & Stouthamer, 2001, p. 89). In this context, the fact that a number of radiocarbon dates indicate end of peat formation on the upper IJssel floodplain in the Roman Period (12 BC -425 AD; Willems, 1986) is not surprising, and may not have been caused by the formation of the IJssel channel, but rather by a regional change in sedimentation style of the Rhine system that probably already started ~3000 cal yr BP (Gouw & Erkens, 2007). Therefore, radiocarbon dates from the lower IJssel floodplain, located well outside the zone of clastic overbank deposition of Rhine branches other than the IJssel, are more indicative of the time of IJssel channel formation.…”