Deriving basin-wide denudation rates of basaltic rocks using cosmogenic Kr isotopes, vulcanic complex Vogelsberg, Germany

The Vogelsberg area in Hessen, Germany, comprises the largest contiguous volcanic complex in Central Europe, covering an area of about 2300 km². After volcanic activity ceased during the mid-Miocene, the complex was subject to extensive erosion and weathering. Fluvial erosion has shaped the area, which is now characterised by Pleistocene valleys and a radial river system exposing primitive alkali basalts and basanites. However, the inference of catchment-wide weathering and erosion rates from the most commonly used cosmogenic nuclide – mineral pair (e.g. 10Be from quartz) remains challenging in such an environment due to the mafic nature and nominally quartz-free composition of the local bedrock. Due to these method-related obstacles only few cosmogenic studies have focused on basaltic regions until now, even though basalt weathering is globally an important CO2 sink.The development and establishment of the novel method using terrestrial cosmogenic krypton (Kr) in the weathering-resistant mineral zircon (Dunai et al. 2022) allows quantification of denudation on quartz-poor lithologies over hundreds of kyr timescales. We exploit the method’s advantage and sampled zircons from sediments of streams radially draining the Vogelsberg and measured Kr isotope abundances to assess the time-integrated erosion patterns shaping the volcanic complex. Integrating over millennial timescales, the 10Be(meteoric)/9Be system will be applied to the same catchments. The 10Be/9Be system can be measured on sediment of any type of lithology including mafic rock (Dannhaus et al. 2018), and thus presents an inter-method validation of the Kr method. We will present the krypton results and discuss basalt weathering in a currently temperate climate through the lens of the different methodological approaches applied. Dunai et al. (2022) Geochronology, https://doi.org/10.5194/gchron-4-65-2022Dannhaus et al. (2018) GCA, https://doi.org/10.1016/j.gca.2017.11.005