Old orogen – young topography: Evidence for relief rejuvenation in the Bohemian Massif
Author:
Wetzlinger Klaus1, Robl Jörg1, Liebl Moritz1, Dremel Fabian1, Stüwe Kurt2, von Hagke Christoph1
Affiliation:
1. Department of Environment and Biodiversity, Division of Geology and Physical Geography , University of Salzburg , Salzburg , Austria 2. Institute for Earth Sciences , University of Graz , Graz , Austria
Abstract
Abstract
The Bohemian Massif is the relic of a major Paleozoic mountain range that is known to have exhumed and its surface levelled in the Permian, but its Neogene landscape evolution is largely unconstrained. The landscape is characterized by rolling hills and extended planation surfaces above an elevation of about 500 m. However, at lower elevations deeply incised gorges confined by steep hillslopes are abundant and contrast impressively with the low relief landscapes above. Rivers with a bimodal morphology (i.e. steep at lower elevations and gentle at higher elevations) drain either to the north into the Vltava (Moldau) River or to the south into the Danube River. Hence, a continental drainage divide runs through the Bohemian Massif. Here, we quantify spatial characteristics of the Bohemian Massif landforms by computing landscape metrics like steepness index or geophysical relief derived from digital elevation models. From this we infer temporal change of the landscape in the past and predict them for the future evolution of the region.
We show that the landscape is characterized by out-of-equilibrium river profiles with knickpoints abundantly at elevations between 450 m and 550 m separating steep channel segments at lower elevations from less steep channels at higher elevations. Hypsometric maxima at or close above knickpoint elevations, along with high and low values in geophysical relief as indicator for the degree of fluvial landscape dissection downstream and upstream of major knickpoints, support the idea of landscape bimodality. Furthermore, we find a distinct drainage divide asymmetry, which causes the reorganization of the drainage network of the region. Across-divide gradients in channel steepness predict the northward migration of the Danube-Vltava drainage divide including growth and shrinkage of tributary catchments, thus controlling changes in the Central European drainage pattern.
All aspects suggest that the region experienced relief rejuvenation during the last few million years. We suggest that this relief rejuvenation is related to the inversion of the Molasse basin with a long wavelength rock uplift pattern and low uplift rates. Vertical motion of crustal blocks at discrete faults may locally affect the uplift pattern. However, the contrasting bedrock properties between the sedimentary cover (Molasse sediments) and the crystalline basement (Bohemian Massif) cause substantial differences in erosion rate and are thus the superior control on the topographic variations of the entire region.
Publisher
Austrian Geological Society (OGG)
Reference88 articles.
1. Badura J., Zuchiewicz W., Štěpančiková P., Przybylski B., Kontny B., Cacoń, S., 2007. The sudetic marginal fault: A young morphophotectonic feature at the NE margin of the Bohemian Massif, Central Europe. Acta Geodynamica et Geomaterialia, 4/4, 7–29 2. Balatka B., Kalvoda J., 2008. Evolution of Quaternary river terraces related to the uplift of the central part of the Bohemian Massif. Geografie. Sbornik Ceské geografické spolecnosti, 113/3, 205–222 3. Baran R., Friedrich A.M., Schlunegger F., 2014. The late Miocene to Holocene erosion pattern of the Alpine foreland basin reflects Eurasian slab unloading beneath the western Alps rather than global climate change. Lithosphere, 6/2, 124–131. https://doi.org/10.1130/L307.1 4. Baumann S., Robl J., Prasicek G., Salcher B., Keil M., 2018. The effects of lithology and base level on topography in the northern alpine foreland. Geomorphology, 313, 13–26. https://doi.org/10.1016/j.geomorph.2018.04.006 5. Bernard T., Sinclair H.D., Gailleton B., Mudd S.M., Ford M., 2019. Litho-logical control on the post-orogenic topography and erosion history of the Pyrenees. Earth and Planetary Science Letters, 518, 53–66. https://doi.org/10.1016/j.epsl.2019.04.034
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