The Saris Transitional Zone, revealing interactions between Pieniny Klippen Belt, Outer Carpathians and European platform

The Pieniny Klippen Belt (PKB) is a narrow structure delineating the boundary between the Central and Outer Carpathians. It is built of nappes stacked during the Cretaceous and Paleocene and then re-folded in the Miocene during the formation of the Outer Carpathian overthrusts. The internal structure of the PKB at the Polish/Slovakian border first formed during northward nappe thrusting processes, which were most intense at the turn of the Cretaceous to the Paleocene. A secondary factor is the change in strike of the PKB turning from W-E to WNW-ESE, associated with dextral strike-slip faulting in the Carpathian basement (North-European Platform). These NNW-SSE oriented strike-slip fault zones, broadly parallel to the Teisseyre-Tornquist Zone, are responsible for the segmentation of the down-going plate, which influenced the subduction and collision between the North-European Platform and the Central Carpathian Block. Among them, the most important role was played by the Krakw-Myszkw Fault Zone separating the Maopolska and Upper Silesian blocks in the Carpathian foreland. Shifts and interactions between the neighboring Pieniny and Outer Carpathian basins-during contemporaneous sedimentation and deformation-resulted in a difficult-to-define, transitional zone. Until now this zone had the rank of a tectonic unit, named Grajcarek Unit in Poland and ari Unit in the Slovak Republic. However, its northern boundary, often taken to represent the Central/Outer Carpathians boundary, is ambiguous. These problems are due to the spatial overlap of thrusting and gravitational flows resulting in chaotic breccias, olistoliths and olistostrome formation, which formed repeatedly and became deformed during the Maastrichtian to Early Miocene. Tectonic deformations in this area gradually vanished towards the north. This zone can therefore be defined as the Peri-Klippen part of the Magura Nappe that lacks a distinct northern tectonic limit. For this reason it is named ari Transitional Zone (TZ).