Allogenic forcing of the late Quaternary Rhine-Meuse fluvial record:: the interplay of sea-level change, climate change and crustal movements

The Rhine-Meuse system in the west-central Netherlands is a continental-scale fluvial system bordered by an extremely wide continental shelf. Consequently; late Quaternary eustatic sea-level changes have resulted in dramatic shoreline displacements, by as much as 800 km. In addition, changes in climate have been severe, given the latitudinal and palaeogeographic setting of the Rhine-Meuse system. We investigated the relative importance of these allogenic controls on fluvial aggradation and incision during the last two glacial interglacial cycles. We used optical dating of quartz from similar to30 samples in a cross-section perpendicular to the palaeoflow direction, allowing us to correlate periods of aggradation and incision with independent records of sea-level change, climate change and glacio-isostatic crustal movements. We found the long-term aggradation rate to be similar to8 cm kyr(-1), a value similar to previous estimates of tectonic subsidence rates in the study area. Several excursions from this long-term aggradation trend could be identified for the last glacial-interglacial cycle. Dry climatic conditions with relatively high sediment supply induced aggradation during oxygen-isotope stages (OIS) 4 and 3. Build-up of a glacio-isostatic forebulge during OIS 2 is a likely cause of incision around the Last Glacial Maximum, followed by an aggradation phase during forebulge collapse. Sea-level highstands during OIS 5 have likely resulted in the aggradation of coastal prisms, but only minor, basal estuarine deposits have been preserved because these coastal prisms were prone to erosion during ensuing sea-level falls. Overall, the sedimentary record is dominated by strata formed during time intervals when the study area was completely unaffected by sea-level control, and our evidence shows that the falling-stage systems tract has the highest preservation potential. Our study highlights the importance of considering the complex interplay of both upstream and downstream controls to obtain a comprehensive understanding of the evolution of basin-margin successions.