Paleomagnetic and magnetic fabric data from Lower Triassic redbeds of the Central Western Carpathians: new constraints on the paleogeographic and tectonic evolution of the Carpathian region

Abstract

In the Central Western Carpathians (CWC), most published paleomagnetic results from Permo-Mesozoic rocks document extensive remagnetizations and come from thin-skinned thrust units that have undergone multistage deformation. We present results from lower Triassic redbeds from the autochthonous cover overlying the basement that carry a primary magnetization. Petromagnetic results indicate that the dominant ferromagnetic carrier is hematite, while magnetic susceptibility and its anisotropy are controlled by both ferromagnetic and paramagnetic minerals. Magnetic fabrics document weak deformation related to Late Cretaceous shortening. The directions of the high unblocking temperature remanence components pass both reversal and fold tests, attesting to their primary nature. Paleomagnetic inclinations are flatter than expected from reference datasets, suggesting small latitudinal separation between the CWC and stable Europe. Paleomagnetic declinations are mostly clustered within individual mountain massifs, implying their tectonic coherence. They show only minor differences between the massifs, indicating a lack of significant vertical-axis tectonic rotations within the studied central parts of the CWC. The paleomagnetic declinations are therefore representative of the whole of the CWC in terms of regional paleogeographic interpretations, and imply moderate counterclockwise rotations (c. 26°) of the region with respect to stable Europe since the Early Triassic.

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

“…Kruczyk et al, 1992;Grabowski and Nemčok 1999;Grabowski et al, 2010). More recently paleomagnetic results were reported from Lower Triassic red beds resting directly upon the Tatric crystalline basement (Szaniawski et al, 2012;2020), which show virtually no rotation in relation to the present north (small black arrows in Fig. 15).…”

“…Kruczyk et al, 1992). However, recently documented primary magnetizations from the Tatric cover Unit (Szaniawski et al, 2012;2020) show concordant paleodeclinations relative to the present north, consistent through a considerable part of the Central Western Carpathians, and therefore challenge the oroclinal bending model.…”

“…They are complemented by sporadic data from the Tatric and Hronic units in the Tatry Mts. (Grabowski 1997;2000;Szaniawski et al, 2012) as well as from the Tatric and Fatric units of the remaining part of the "core mountains": Nízke Tatry, Malá Fatra, Veľká Fatra (Kruczyk et al, 1992;Pruner et al, 1998;Szaniawski et al, 2020), Strážovské vrchy Mts. (Grabowski et al, 2009;Szaniawski et al, 2020) and Malé Karpaty Mts.…”

“…Exceptions are the Lower Triassic siliciclastic deposits resting directly upon the Tatric crystalline basement (Szaniawski et al, 2012;2020) and Berriasian pelagic limestones of the Fatric Unit (Grabowski 2005;Grabowski and Pszczółkowski, 2006;Grabowski et al, 2009;2010) where magnetization has been interpreted as primary. Unlike the Cenozoic paleomagnetic directions showing consistent 50-60° CCW rotations in all principal tectonic units of the Western Carpathians (see comprehensive review by Márton et al, 2016), the pre-Cenozoic paleodirections display a more complex pattern.…”

“…Green and yellow, not numbered circles with arrows are for Gosau Group and CCPB sediments from the same overview. Short black arrows are locality mean directions obtained for Lower Triassic sandstones of the Tatric cover Unit interpreted as primary (Szaniawski et al, 2020).…”