A composite terrain-and-provenance analysis tied to specific times of a basement-foreland drainage system and its gravel-sand-clay deposits (Bohemian Massif, SE Germany)

Abstract

Provenance analysis and terrain analysis backed by radiometric age dating have been combined for the first time and conducted as a composite in a foreland-basement transition zone with mutual benefits for both disciplines. A meticulous provenance analysis enables a fine-tuning during studies of the landscapes and relief generations, while a detailed terrain analysis is essential for the disentanglement of lithological-geodynamic processes that often are telescoped into each other by sedimentological processes. The basic drivers for the denudation, transport and deposition processes of the various clast communities (gravel, sand, clay) are the climate change from a tropical (Neogene) to a glacial/temperate Earth and the brittle neotectonics along the margin of the study area (Rhine Graben Rift N-S, Eger/Ohře Graben Rift E-W). As a result of this composite approach the landscape formation in the study area is described as follows: (1) (Paleogene)-Neogene peneplanation in the basement, (2) Quaternary straight to low sinuosity drainage in the basement, (3) Late Pleistocene to Holocene high-sinuosity drainage in the proximal foreland and (4) Holocene (to Late Pleistocene) meandering fluvial rivers evolving in the distal foreland. In additions to these geomorphological results progress can be made in the geodynamic evolution of the study/source area. Five Proterozoic to Late Paleozoic lithological units are identified: (1) Para-metamorphic rocks, (2) greenstones, (3) basic volcano-sedimentary rocks, (4) sedimentary units abundant in chert and (5) felsic volcanics. By means of these sedimentological finds a more detailed picture of the Variscan orogeny can be presented.