Differential subsidence within a coastal prism : late-Glacial - Holocene tectonics In The Rhine-Meuse delta, the Netherlands

Abstract

The Rhine-Meuse river system has been studied extensively over the past few decades. The Netherlands' coastal prism formed in response to Holocene sea level rise and buried the Weichselian (OIS-2) Rhine-Meuse valley. Although the geological-geomorphological evolution of the Rhine-Meuse system since the Last Glacial Maximum (ca. 22 kyr cal BP) is known in great detail, the effects of neotectonics in the Rhine-Meuse delta have only been recognised recently. In this thesis the Rhine-Meuse record over the last 15,000 years is used to quantify subsidence in the central Netherlands. The thesis brings new evidence on the spatially and temporally non-linear rates of differential subsidence in the central Netherlands. The Late-Glacial / Holocene active faults have been identified in the fluvial deposits of the last 15,000 years. Deformation is quantified from post-depositional deformations of gradient lines. Quantification is done in two ways: (1) by analysing longitudinal profiles of paleo channel belts and (2) by geostatistically reconstructed paleo-groundwater surfaces from basal-peat radiocarbon dates. Syn-depositional effects of active differential subsidence to active fluvio-deltaic deposition are identified, and are used to further constrain differential subsidence in time and space. The results support a forebulge hypothesis: the Late-Glacial - Holocene Rhine-Meuse delta appears to be on the southern flank of a collapsing Weichselian forebulge in the North Sea basin, related to Scandinavian and British ice-sheets. The thesis comes with a full-colour map of the central Rhine-Meuse delta and a cross-section spanning the full delta width, and covering all Rhine and Meuse channel belts since the last glacial maximum