Geology and tectonics of the contact zone of the Central and External Carpathians in western Slovakia – a review of new results and conceptions

New data gathered in the Pieniny Klippen Belt (PKB) and adjacent zones along the Central–External Carpathians boundary in western Slovakia allow for a formulation of an updated model of its structure and tectonic evolution. In general, these zones evolved as an accretionary complex in front of the prograding Central Western Carpathian orogenic wedge during the latest Cretaceous to Paleogene. Step-by-step forward accretion of Oravic units of the PKB (Šariš, Subpieniny, Pieniny) with piggyback frontal elements of the Fatric units (Drietoma, Manín, Klape) was followed by incorporation of the External Carpathian Biele Karpaty and Magura units and brought about transfer of the Oravic elements from the wedge tip to its rear. The wedge growth was accompanied by steepening of the PKB structures up to final overturning and backthrusting to the south in places. By this process, the PKB were ultimately placed in the centre or southern limb of an asymmetric fan-wise accretionary wedge, i.e. in a backstop position between the wedge and rigid Central Carpathian block. Consequently, the original fold-and-thrust structures of the PKB were modifi ed or largely obliterated by superimposed out-of-sequence thrusting, transpressional and transtensional deformation. In addition to a rather poor brittle structural record that is mostly related to younger post-thrusting deformation, these processes are nicely registered by synorogenic clastic sediments in both the trench-foredeep basins in the lower plate of the convergent system (Oravic units) and in the piggyback, wedge-top basins above the deformed wedge (Gosau-type basins). Sedimentary record in the wedge-top area is diff erentiated into several transgression/regression cycles that are interpreted in terms of the critical wedge theory.New data gathered in the Pieniny Klippen Belt (PKB) and adjacent zones along the Central–External Carpathians boundary in western Slovakia allow for a formulation of an updated model of its structure and tectonic evolution. In general, these zones evolved as an accretionary complex in front of the prograding Central Western Carpathian orogenic wedge during the latest Cretaceous to Paleogene. Step-by-step forward accretion of Oravic units of the PKB (Šariš, Subpieniny, Pieniny) with piggyback frontal elements of the Fatric units (Drietoma, Manín, Klape) was followed by incorporation of the External Carpathian Biele Karpaty and Magura units and brought about transfer of the Oravic elements from the wedge tip to its rear. The wedge growth was accompanied by steepening of the PKB structures up to final overturning and backthrusting to the south in places. By this process, the PKB were ultimately placed in the centre or southern limb of an asymmetric fan-wise accretionary wedge, i.e. in a backstop position between the wedge and rigid Central Carpathian block. Consequently, the original fold-and-thrust structures of the PKB were modifi ed or largely obliterated by superimposed out-of-sequence thrusting, transpressional and transtensional deformation. In addition to a rather poor brittle structural record that is mostly related to younger post-thrusting deformation, these processes are nicely registered by synorogenic clastic sediments in both the trench-foredeep basins in the lower plate of the convergent system (Oravic units) and in the piggyback, wedge-top basins above the deformed wedge (Gosau-type basins). Sedimentary record in the wedge-top area is diff erentiated into several transgression/regression cycles that are interpreted in terms of the critical wedge theory

Geology and tectonics of the contact zone of the Central and External Carpathians in western Slovakia – a review of new results and conceptions

New data gathered in the Pieniny Klippen Belt (PKB) and adjacent zones along the Central–External Carpathians boundary in western Slovakia allow for a formulation of an updated model of its structure and tectonic evolution. In general, these zones evolved as an accretionary complex in front of the prograding Central Western Carpathian orogenic wedge during the latest Cretaceous to Paleogene. Step-by-step forward accretion of Oravic units of the PKB (Šariš, Subpieniny, Pieniny) with piggyback frontal elements of the Fatric units (Drietoma, Manín, Klape) was followed by incorporation of the External Carpathian Biele Karpaty and Magura units and brought about transfer of the Oravic elements from the wedge tip to its rear. The wedge growth was accompanied by steepening of the PKB structures up to final overturning and backthrusting to the south in places. By this process, the PKB were ultimately placed in the centre or southern limb of an asymmetric fan-wise accretionary wedge, i.e. in a backstop position between the wedge and rigid Central Carpathian block. Consequently, the original fold-and-thrust structures of the PKB were modifi ed or largely obliterated by superimposed out-of-sequence thrusting, transpressional and transtensional deformation. In addition to a rather poor brittle structural record that is mostly related to younger post-thrusting deformation, these processes are nicely registered by synorogenic clastic sediments in both the trench-foredeep basins in the lower plate of the convergent system (Oravic units) and in the piggyback, wedge-top basins above the deformed wedge (Gosau-type basins). Sedimentary record in the wedge-top area is diff erentiated into several transgression/regression cycles that are interpreted in terms of the critical wedge theory.New data gathered in the Pieniny Klippen Belt (PKB) and adjacent zones along the Central–External Carpathians boundary in western Slovakia allow for a formulation of an updated model of its structure and tectonic evolution. In general, these zones evolved as an accretionary complex in front of the prograding Central Western Carpathian orogenic wedge during the latest Cretaceous to Paleogene. Step-by-step forward accretion of Oravic units of the PKB (Šariš, Subpieniny, Pieniny) with piggyback frontal elements of the Fatric units (Drietoma, Manín, Klape) was followed by incorporation of the External Carpathian Biele Karpaty and Magura units and brought about transfer of the Oravic elements from the wedge tip to its rear. The wedge growth was accompanied by steepening of the PKB structures up to final overturning and backthrusting to the south in places. By this process, the PKB were ultimately placed in the centre or southern limb of an asymmetric fan-wise accretionary wedge, i.e. in a backstop position between the wedge and rigid Central Carpathian block. Consequently, the original fold-and-thrust structures of the PKB were modifi ed or largely obliterated by superimposed out-of-sequence thrusting, transpressional and transtensional deformation. In addition to a rather poor brittle structural record that is mostly related to younger post-thrusting deformation, these processes are nicely registered by synorogenic clastic sediments in both the trench-foredeep basins in the lower plate of the convergent system (Oravic units) and in the piggyback, wedge-top basins above the deformed wedge (Gosau-type basins). Sedimentary record in the wedge-top area is diff erentiated into several transgression/regression cycles that are interpreted in terms of the critical wedge theory

The Pieniny Klipp en Belt – structure, evolution and position in the Carpathian tectonic framework

The current tectonic research in the western and eastern Slovakian parts of the Pieniny Klippen Belt (PKB) has revealed some important differences between these two segments. The western PKB segment is characterized, in addition to the presence of ubiquitous Oravic units, by a broad incorporation of frontal elements of the Central Carpathian Fatric cover nappe system (Manín, Klape, Drietoma nappes). These are overstepped by still synorogenic, Gosau-type Senonian–Palaeogene basins. On the contrary, the northern and eastern PKB parts are dominated by the Oravic complexes representing an independent, originally intra-Penninic palaeogeographic element. Though strongly affected by Miocene along-strike wrench movements, several PKB sectors still preserve original fold-andthrust structures that developed sequentially in a piggy-back manner during the Late Cretaceous to Early Eocene times. Timing of these thrust events is facilitated by the presence of syntectonic sediments in the footwalls of thrust sheets, as well as by overstep complexes sealing older structures. The syntectonic sediments typically include olistostromes and huge olistolites derived from the overriding nappe fronts. In such a way, three principal Oravic units have been recently defined in the eastern Slovakian PKB – the Šariš, Subpieniny and Pieniny nappes

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