U-Pb-He detrital zircon double dating of Cretaceous synorogenic sandstones of the Eastern Alps

The Cretaceous period of the European Alps is constrained mostly by thermobarometric and geochronologic data obtained on metamorphic basement units complemented by investigations on the sedimentary record. Our advanced sediment provenance approach using detrital zircon double-dating reveals high- and low-temperature age constraints that allow for (i) assigning potential source formations to Cretaceous siliciclastic sequences of the Eastern Alps and (ii) derive a model of sediment pathways through space and time.

We performed U-Pb-He double dating on 970 detrital zircon grains from 12 samples, deposited from Early Cretaceous to early Eocene in the Eastern Alps. Additionally two reference samples from the Alps and from the Bohemian Massif were also dated. The detrital U-Pb age spectra are compared to published zircon U-Pb age distributions obtained on the potential source units. The Fflysch and Gosau samples show different age patterns: while the Flysch shows strong similarities to age patterns obtained on the Bohemian Massif, the characteristic Variscan and Caledonian age components are largely missing in the Gosau samples. The (U-Th)/He low-temperature cooling ages form three, well distinguishable age groups: 250-180 Ma, indicating provenance from the European craton; 160-100 Ma, indicating Upper Austroalpine hanging wall units and the Jurassic nappe complex; and 70-50 Ma hinting to the Austroalpine core complexes. The Flysch is dominantly European in origin with some Alpine detritus, while the Gosau sediment derived mostly from the Eoalpine core complexes. We present a reconstruction of the sediment supply pathways in four time slices for the Early Cretaceous to Paleogene Eastern Alps.