Detrital rutile geochronology of the Vahic Superunit helps to understand the closure of the Alpine Tethys in the Western Carpathians

The Vahic Unit represents a critical tectonic element of the Western Carpathians, proposed as the oceanic suture zone that separates the Central Western Carpathian (CWC) block from the North Europeanplatform. Interpreted as the eastern continuation of the South Penninic (Alpine Tethys) oceanic domain, the Vahicum is primarily represented by the Belice Unit, which preserves a sedimentary record of the Vahic Ocean's evolution. This sequence includes Upper Jurassic radiolarites and Lower Cretaceous pelagic limestones, conformably overlain by Upper Cretaceous flysch.

Structurally, the Vahicum occupies the lowermost position in the orogenic wedge, situated beneath the Tatric crystalline basement. It is believed that the closure of the Vahic Ocean occurred during the Late Cretaceous (Late Turonian to Maastrichtian), marked by the subduction of oceanic and attenuated continental crust beneath the prograding CWC overriding plate. This process was supposed to result in high-pressure/low-temperature (HP/LT) metamorphism, typical of Penninic-type subduction zones, although these signals are often fragmented due to subsequent tectonic reworking, and in larger scale non existent.

In this study, six sandstone samples were collected from the Vahic Unit to investigate, through a detrital rutile geochronological campaign, its tectonic and sedimentological evolution. From each sample, approximately 200 rutile grains were extracted, with roughly half selected for detailed age and trace element analysis.

These findings are compared with previously acquired data from the Magura and Silesia supernits to constrain regional provenance better. In the Magura transect, prominent age peaks align with Variscan (c. 400–280 Ma) and Alpine (c. 160–90 Ma) events, including dominant Alpine maxima at 137–126 Ma and 115–105 Ma. In contrast, the Silesian samples consistently exhibit a prominent Variscan peak, with Alpine tectonic signatures (e.g., a dominant peak at 95 Ma) appearing only in the young, Oligocene deposits. Integrating the rutile age data from the Vahic Superunit into this regional framework allows for a more comprehensive reconstruction of the evolving paleodrainage and tectonic maturation of the Carpathian orogenic wedge.