S U M M A R YThe Carpathians belong to the European Alpine system, which was formed during the convergence and collision of the European and African plates. The study area, which comprises the Magura and Silesian nappes of the Outer Western Carpathians, were the locations of intensive folding and nappe transport during the Tertiary. There are a number of models depicting the changes in shapes and positions of the original sedimentary basins as a consequence of the above processes. However, it is this study that provides the first palaeomagnetic constraints for reconstructing the displacement history of the Silesian and Magura nappes during Tertiary.For the palaeomagnetic and anisotropy of the low-field magnetic susceptibility (AMS) studies 554 independently oriented cores were drilled, mostly from claystones, at 57 geographically distributed localities of Oligocene (and partly of Late Eocene in the Magura nappe) age. In the laboratory, the magnetic mineral identified was always magnetite, invariably accompanied by paramagnetic pyrite. The AMS measurements showed that the magnetic fabric was dominantly foliated. The foliation and bedding poles were very close at most of the localities, suggesting that the foliation was of sedimentary/compaction origin. Magnetic lineations, even if clustered at the locality level, did not exhibit a regional pattern for the Magura nappe. On the other hand, lineations related to folding were NE-SW oriented in the western and E-W oriented in the central and eastern segments of the Silesian nappe. Following the AMS measurements the samples were subjected to detailed stepwise demagnetization and analysis of the demagnetization curves that provided the input data for regional tilt tests. Both the tilt and inclination only tests suggested that the remanence is of post-folding age for the Magura nappe, showing a general 50 • counterclockwise (CCW) rotation. Similar palaeomagnetic directions were observed for the central and eastern segments of the Silesian nappe, whereas a significantly larger CCW rotation for the western segment. The orientations of the AMS lineation directions averaged for the central, the eastern and the western segments of the Silesian nappe correspond to a 'rotated' palaeomagnetic pattern, as they are practically E-W oriented for the first two and NE-SW oriented for the third.The palaeomagnetic results of this study are interpreted in terms of a 50 • 'en bloc' rotation in the CCW sense of the Magura and Silesian nappes during their Miocene emplacement. This result has two important implications. The first is that the CCW rotation of the nappes that accompanied the displacement of the flysch basins from SW to NE is not of Palaeogene age, as earlier suggested, but younger. The second is that the change in the stress field orientation during the Miocene, observed for the Silesian nappe is not a CW far field stress rotation, but the consequence of CCW block rotations. The larger CCW rotation observed in both the palaeomagnetic and AMS data sets for the western segment of ...

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AMS studies earlier carried out on the flysch sediments from the Outer Western Carpathians focused on the sandstone members deposited from turbidity currents. The main conclusion of these studies was that the dominant features of the AMS fabric developed during sedimentation and the tectonic overprint was weak. In recent years a large number of claystone (deposited also from turbidity currents, but in calm water) localities were sampled from the Krosno beds of the Silesian nappe, primarily for paleomagnetic study. Nevertheless, the AMS of the samples was also measured. The magnetic fabrics of the claystones were dominated by foliation, but lineations were also expressed and attributed to deformation. The question arose how different are the reactions of the claystone and the siltstone beds to deformation.Comparison was made between the upper, finest grained part of sandstone beds and claystones from the same outcrops of the Silesian nappe. It was found that the AMS ellipsoids for different lithologies were coaxial. The main difference was the higher degree of foliation in the claystones than in the siltstones which was attributed to stronger compaction in the former. Surprisingly, there was practically no difference in the degrees of lineation between the different lithologies from the same outcrop, suggesting that the siltstones and the intercalated claystones similarly react to tectonic deformation. Siltstone and claystone samples from a single outcrop from the Skole nappe behaved differently, since the siltstone had inverse fabric due to impregnation by siderite.It seems that the claystones of the flysch sequences, although technically more difficult to work with them, have advantages over the sandstones/siltstones when the goal of the AMS measurements is the study of deformation. One of the good aspects of the claystones is that their primary fabric is probably not or weakly oriented by paleocurrents. Therefore, the AMS lineation and the stress field orientation have a straightforward relation, while the sandstones often have a composite fabric, since it is the well developed flow oriented sedimentary fabric which is overprinted by deformation. The second is that the permeability of claystones is lower, thus secondary infiltration and impregnation by E. Márton et al. 122Stud. Geophys. Geod., 54 (2010) iron minerals dramatically influencing the orientation of the AMS fabric, as it was observed for the siltstones from a single locality from the Skole nappe, is practically impossible.