Synthrusting remagnetization of the Krížna nappe: high resolution palaeo- and rock magnetic study in the Strážovce section, Strážovské vrchy Mts, Central West Carpathians (Slovakia)

Abstract

Palaeomagnetic studies of the uppermost Jurassic to lower Cretaceous pelagic carbonates in the Krížna nappe in the Strážovske vrchy Mts (Central West Carpathians, Slovakia) revealed the presence of secondary magnetite-related magnetization of exclusively normal polarity (component b), which was most probably acquired during the thrusting episode in the late Cretaceous. three formations exposed in the Strážovce section were the subject of investigation: Jasenina (Kimmeridgian–tithonian), osnica (lower–Middle berriasian) and Mraznica (Upper berriasian–hauterivian). Component b is ubiquitous throughout the section but is strongest in the Mraznica formation. this formation contains a lot of superparamagnetic particles and shows rock magnetic characteristics typical of chemically remagnetized carbonates. the remaining two formations, although also remagnetized, bear traces of an older, probably primary magnetization (component C). the fold test for component b is apparently positive; however the inclination in pre-folding coordinates is too steep for any expected palaeoinclination of Jurassic to recent age. additional tectonic correction must be applied to match the palaeoinclinations with expected values. although there is some uncertainty in this additional correction, all plausible options suggest that the rocks must have been magnetized when they dipped in the opposite direction to the thrusting direction. this interpretation is concordant with the internal tectonics of the Krížna nappe, consisting of imbricated units of duplex-type structure.