Asymmetric river incision records the Quaternary uplift of the Rhenish Massif

The topography of the Rhenish Massif is known to be affected by Late Cenozoic uplift. Recent GNSS studies imply surface uplift rates of up to 1 mm/a, likely controlled by a mantle plume beneath the Eifel. Studies on Rhine River terraces show that central parts of the Rhenish Massif have been uplifted by 140 to 250 m since 700-800 ka. These figures correspond to a very low long-term average uplift rate of 0.1-0.3 mm/a, which decrease to even lower rates towards the margins of the Rhenish Massif. There, conventional geomorphic analyses, such as K_SN values, Chi-maps and basin asymmetries, show no evidence of vertical motions.

Field observations in several valleys of the Diemel river catchment in the northeastern Rhenish Massif show steeper west-facing topographic slopes compared with flatter east-facing slopes, suggesting asymmetric bedrock incision due to ongoing surface uplift. We analysed topographic river profiles on a regional scale in five catchments (Möhne, Alme, Ruhr, Diemel and Eder) using 1 m-resolution Lidar data to see whether they are affected by asymmetric river incision Our results show that only the S-N oriented streams cutting into lithologically heterogeneous rock formations show asymmetric incision. This pattern resulted from uplift and tilting of the Rhenish Massif towards the NE, causing differential erosion.

These preliminary results will be substantiated by a more regional study comprising the entire margin of the Rhenish Massif. We aim to investigate whether the slow vertical surface movements around the Eifel Plume could have led to asymmetric bedrock incision elsewhere, too.