Palaeomagnetism of some Devonian carbonates from the Holy Cross Mts. (Central Poland): large pre-Permian rotations or strain modified palaeomagnetic directions?

Abstract

Palaeomagnetic studies of Middle and Upper Devonian carbonate rocks in the Holy Cross Mts. (Central Poland, SW foreland of the East European Craton — EEC) involved samples from the southern (Kielce) and northern (Łysogóry) unit. Haematite-bearing carbonates showed syn-folding remagnetisation of Early Permian age. The pole of this component is situated on the apparent polar wander path (APWP) of the EEC. The syn-folding age implies deformation of the Variscan syncline during Alpine uplift of the Holy Cross Mts. In dark limestones and dolomites magnetite was a dominant magnetic mineral. The age of magnetisation is interpreted as pre-Late Carboniferous: syn-folding in one locality and either pre- or syn-folding in four others. Four poles calculated from these components are shifted to the NW from the reference southern APWP for the EEC and one pole is concordant with its Early Carboniferous segment. The occurrence of rotated and unrotated palaeomagnetic poles could indicate that some fragments of both Kielce and Łysogóry units were subjected to local clockwise rotations during Variscan compression. An alternative explanation might be that Variscan pre- and/or syn-folding components could be strain modified or resultant magnetisations and they should not be used in palaeotectonic reconstruction.