Impact of the Mid-Pleistocene Transition on Meuse River Terraces in the Southern Netherlands: New Terrace Burial Ages

Abstract

River terrace deposits are excellent archives of paleoenvironmental conditions. They reflect the tectonic and climatic settings of their time of formation. For this reason, Late-Pleistocene and Holocene terraces have been previously studied in detail because of their good state of preservation and age control. However, less is known about the Middle- and Early-Pleistocene terraces. The Lower Meuse River, a major tributary of the Rhine River, located in the Southern Netherlands, exhibits a well-preserved terrace staircase which, for decades, has been intensely investigated. Age constraints are available, which are mainly based on correlations to the marine isotope record. As of late, the availability of numerical ages of these terraces have been increasing, allowing for a better determination of the boundaries of the Early, Middle and Late Pleistocene terraces. In order to better understand the effects of the Mid-Pleistocene Transition (MPT; 1.2 – 0.8 Ma) in the Meuse River, we improved the spatial and temporal resolution of the terraces of the Lower Meuse. For the spatial resolution, we used a dense borehole database to characterize key geometrical and compositional parameters of the different terrace levels. For the temporal resolution, we used cosmogenic-nuclide geochronological methods, relying on the measurements of the paired isotopes 26Al-10Be, allowing for the estimation of terraces burial age. In this work we outline general spatial trends of geometrical and compositional parameters of terraces formed pre-, syn-, and post-MPT. These results are displayed in an improved time framework that relies upon the new burial ages results from the cosmogenic nuclides concentration measured for specific terrace levels. We present three new isochron-burial ages from Main Terrace levels, and thirteen new simple-burial ages from Middle-, Main-, and East Meuse-Terraces. The results allow us to better understand the signal propagation generated by the MPT. A general increasing trend in the gravel content and terrace thickness have been observed from older to younger terraces. The ages are mostly in good agreement (within uncertainty) with previously proposed age models, especially the ages for the East Meuse Terraces, which have been confirmed to be Early Pleistocene.