Denudation, erosion and weathering rates from meteoric cosmogenic nuclides in the basaltic volcanic field of the Vogelsberg, Germany

Accurate projections of climate tipping points require quantitative constraints on the nature and strength of feedbacks within the Earth’s surface carbon cycle. Among these, silicate weathering constitutes a key negative feedback by consuming atmospheric CO₂ through mineral dissolution. However, the feedback’s climatic sensitivity, expressed by the dependence of weathering rate on climate, remains poorly quantified. Basalt weathering plays an outstanding role in this process, due to basalt’s high abundance of CO₂-sequestering elements. For instance, increased basalt weathering fluxes may have caused global Cenozoic cooling. Determining weathering rates is key to this quantification. However, the quartz-free nature of basalt precludes the use of common in-situ cosmogenic nuclide approaches. We thus use the ¹⁰Be_meteoric/⁹Be cosmogenic nuclide method that has emerged as a powerful tool to simultaneously capture both physical erosion and chemical weathering in basaltic landscapes over millennial timescales.

We applied the ¹⁰Be_meteoric/⁹Be method to determine catchment-averaged denudation rates on river bedload and river waters, and local soil weathering rates on weathering profiles in the Vogelsberg (Germany). Denudation rates are consistent (~50 t km⁻² yr⁻¹ in rivers, ~40 t km⁻² yr⁻¹ in soils) and align with rates from other temperate basaltic regions. Weathering rates and intensities are high compared to other lithologies, which underlines the high reactivity of basalt. This first application of the method in basalt demonstrates its ability to simultaneously quantify denudation and weathering from multiple sample types. Extending this approach to other climates will help establish a baseline for detecting nonlinear or tipping responses in Earth’s surface carbon cycle.