Quantifying river incision and uplift in the Rhenish Massif by dating of fluvial terraces in the Rhine Valley using the 10Be–26Al burial dating method

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The Rhenish Massif is a prominent example for a region with well preserved sequences of river terraces. These terraces formed by the incision of the Rhine and its tributaries into the Paleozoic bedrock. The youngest terrace above the narrow and steep Rhine valley – the so-called Younger Main Terrace – constitutes an important geomorphological marker, for which an age of 700-800 ka is assumed based on paleomagnetic data. Using this age and the height of the Younger Main Terrace above the Rhine, a model for river incision and uplift of the Rhenish Massif was developed, which predicts an abrupt increase in the rate of incision and uplift at 700-800 ka. In contrast, an alternative model, which is based on the identification of a larger number of Main Terraces by several hundred drillings and a correlation of the entire terrace sequence of the Rhine with paleoclimate records, indicates an older age of ca. 1.3 Ma for the Younger Main Terrace. This model implies slower and nearly constant rates of uplift and incision in the Rhenish Massif. To better constrain the uplift and incision history and to decide which model is correct, absolute age determinations for the Main Terraces of the Rhine are required. Such age constraints are, however, still missing. To quantify the history of river incision and uplift of the Rhenish Massif, we will date the most important Main Terraces in the plateau valley of the Rhine by applying 10Be–26Al burial dating. This innovative and still rarely used method allows dating fluvial terrace deposits in the age range of 0.4 to 5 Ma, even if the terraces lack a well-preserved surface due to erosion, deposition of younger cover sediments, and/or anthropogenic influence. As confirmed by our preliminary investigations, the terrace sediments of the Rhine are very well suited for this kind of age dating. The planned project will provide the first absolute time constraints for the Main Terraces along the Rhine at seven carefully selected sites. With these age constraints it will be possible to reconstruct the incision history of the Rhine and the tectonic uplift history of the Rhenish Massif in unprecedented detail and to relate the uplift to geodynamic causes. In particular, clarifying the age of the Younger Main Terrace has far-reaching consequences, because in the past several studies were based on the assumption of an age of 700-800 ka. Therefore, the results of this project will not only be relevant for reconstructing the incision and uplift history of the Rhenish Massif, but also for studies on landscape evolution, mass balances, neotectonics, and time-dependent models for the uplift.