Anisotropy of magnetic susceptibility as an indicator for palaeocurrent analysis in folded turbidites (Outer Western Carpathians,Poland) |
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| Authors: | Aleksandra Stachowska Maciej Łoziński Michał Śmigielski Anna Wysocka Leszek Jankowski Piotr Ziółkowski |
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| Institution: | 1. Institute of Geological Sciences, Polish Academy of Sciences, 51/55 Twarda Street, 00-818 Warsaw, Poland;2. Faculty of Geology, University of Warsaw, 93 Żwirki & Wigury Street, 02-089 Warsaw, Poland;3. Polish Geological Institute – National Research Institute, Carpathian Branch, 1 Skrzatów Street, 31-560 Cracow, Poland |
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| Abstract: | The anisotropy of magnetic susceptibility is a well-known geological proxy in revealing the directional tectonic and sedimentological features of rocks, although it can be ambiguous in situations where these two factors co-occur. This paper demonstrates the usefulness of the anisotropy of magnetic susceptibility in determining palaeotransport directions in turbiditic rocks that underwent subsequent thrusting and folding. This study demonstrates that the magnetic lineation is largely unsuitable as a palaeocurrent direction proxy, and suggests that the imbrication of magnetic foliation is better in such cases. Moreover, the anisotropy of magnetic susceptibility results were analyzed in reference to a joint and fold study within the framework of the regional structural geology. Magnetic fabric investigations were conducted in the eastern part of the Outer Western Carpathians (south-east Poland). During the study, a total of 191 oriented palaeomagnetic samples were collected from three outcrops (Nasiczne, Dwernik and Hoczew) in the Krosno Beds, Silesian Unit. For the purpose of sedimentological analysis, 121 m of turbidite successions were documented and 126 directional sedimentary structures were measured. The magnetic anisotropy of sandstones revealed typical sedimentary fabrics, often overprinted by variably intense tectonic deformation. Oblate susceptibility ellipsoids from Nasiczne showed tilt coherent with the palaeoflow direction, whereas the rocks from Dwernik and Hoczew contained triaxial magnetic fabric developed during compressional palaeostress. This paper suggests that medium-grained and coarse-grained sandstones, preferably with high mica content, are the most suitable for palaeotransport reconstructions among the studied lithologies. |
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| Keywords: | Anisotropy of magnetic susceptibility (AMS) joint and fold analysis Outer Western Carpathians palaeocurrents turbidites |
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