New paleomagnetic constraints for the large-scale displacement of the Hronic nappe system of the Central Western Carpathians

The thin-skinned Hronic nappe system represents the structurally highest tectonic unit in the Late Cretaceous thrust-stack of the Central Western Carpathians. It mostly comprises a Permian volcano-sedimentary sequence and Triassic carbonate sediments which crop out in different parts of the Central Western Carpathians. We carried out a systematic paleomagnetic study on 24 Permian and 20 Triassic localities geographically distributed over 300 km in W-E direction. Several samples from each locality were drilled and oriented in-situ and specimens cut from them subjected to standard paleomagnetic and magnetic mineralogy experiments. The results were evaluated using principal component analysis, statistical evaluation of the characteristic remanences, and applying inclination-only and tilt tests. We documented the pre-tilting age of remanences for the majority of both the Permian and Triassic age groups. However, the latter was interpreted as remagnetized during the Cretaceous Normal Super-Chron in the course of nappe stacking between 90-80 Ma. The Permian group is exhibiting about 70°, the Triassic about 34° clockwise vertical axis rotations with respect to the present north. There is no indication in our data set for oroclinal bending of the Hronic Unit. We interpret the difference in clockwise rotations (about 36°) between Permian and 90-80 Ma as a clockwise block rotation taking place during major extensional and/or compressive events between stable Europe and Africa. Taking into consideration the well-documented counterclockwise rotation observed for the overstep sequences in the Central Western Carpathians and in the Pieniny Klippen Belt, the remagnetization of the Triassic sediments was closely followed by about 94° clockwise rotation. Research in progress will serve to decide if this large clockwise rotation involved the whole Central Carpathian nappe stack or part of this was due to the thin-skinned nappe emplacement of the Hronic Unit

Provenance of synorogenic deposits of the Upper Cretaceous–Lower Palaeogene Jarmuta–Proč Formation (Pieniny Klippen Belt, Western Carpathians)

The Pieniny Klippen Belt contains thickening and coarsening upwards synorogenic sedimentary successions witnessing the collision of the Oravic ribbon continent with the Central Carpathian orogenic wedge after the closure of the Vahic Ocean in the Late Cretaceous to Early Palaeogene. The sedimentary record of this event is represented by flysch/wildflysch deposits of the Maastrichtian–Lower/Middle Eocene Jarmuta–Proč Formation. We present results of the provenance study of these deposits, based on the framework petrography, heavy mineral analysis and mineral chemistry. Turbiditic sandstones were classified as quarzolithic to lithic arenites. Lithic fragments are predominantly composed of carbonate rocks and low- to medium-grade metamorphic and occasional mafic volcanic rocks. The heavy mineral association is composed of both first-cycle derived and recycled ultrastable ZTR, garnets and Cr-spinels. The chemistry of the detrital tourmalines and garnets suggests a derivation from various low- to medium-grade metamorphic rocks. High-pyrope garnets, observed in the eastern part of the PKB, which were derived from high-grade granulites and eclogites, represent probably lower crustal complexes exhumed during rifting of the Vahic Ocean. The Cr-spinels show a mixed harzburgitic and lherzolitic provenance. The harzburgitic Cr-spinels might have been recycled from older exotic conglomerates of the Klape Flysch, thereby representing ophiolitic detritus of the Meliata Ocean. The lherzolitic Cr-spinels might represent a new contribution of ophiolitic detritus delivered from the exhumed subcontinental mantle forming the Vahic oceanic floor