Ambiguity of provenance studies in complex source-to-sink settings – sediment recycling, basement exhumation and signal mixing in the Schilfsandstein (Central European Basin)

Provenance studies in the Central European Basin are challenged by the complex geology of source areas. The Variscan orogen represents a puzzle of Cadomian terranes, Variscan-aged domains and Palaeozoic sediments with Baltica-/Gondwana-derived detritus. The Caledonian-Fennoscandian source area comprises the Caledonian Belt, Archean to Neoproterozoic domains (Baltica), Variscan molasse sediments and Permo-Carboniferous igneous rocks.

The low-maturity Schilfsandstein (Stuttgart Formation), composed of first- and second-cycle sands, is an ideal candidate to evaluate provenance tools in a complex setting. Within a basin-scale study, subsurface facies maps, heavy minerals, and U-Pb zircon ages were applied to samples from Germany and onshore UK. Results show that the Schilfsandstein represents variable mixtures of recycled sediments and eroded basement. Heavy minerals are dominated by the Gt-Zr assemblage in North Germany (Fennoscandia), by the Ap-Zr-Ep assemblage in southern NW Germany (Rhenish Massif), and by Gt-Zr, Ap-Zr or Ap-Gt-Zr assemblages in Central and South Germany (Bohemian Massif, Vindelician Land). The clear discrimination of Variscan and Fennoscandian sources based on heavy minerals and subsurface facies maps is less constrained by zircon age spectra. Samples from North Germany either show a mix of Fennoscandian and Variscan spectra or typical Variscan spectra comparable to spectra of samples from Central and South Germany. The statistically identical age spectra of samples from North and South Germany (except UK) suggests mixing of source signals in Schilfsandstein rivers or recycling of Variscan molasse sediments in Fennoscandian catchment areas. The results show that complex source-to-sink settings need integrated approaches, individual provenance tools may lead to ambitious results.