The results of paleostress analyses in the eastern parts of the Nízký Jeseník and the Drahany Uplands


Authors: Havíř J

Published in: Bulletin of Geosciences, volume 75, issue 1; pages: 27 - 32;

Keywords: brittle deformation, faults with striations, paleostress analyses, Nízký Jeseník area, Drahany Uplands, Variscides,

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The orientation of the principal paleostress axes were studied in the Culmian sediments in the eastern parts of the Nízký Jeseník area (the Moravice and the Hradec-Kyjovice Formations) and of the Drahany Uplands (the Myslejovice Formation). The paleostress analyses were based on the fault geometry investigation. Several different Variscan paleostress fields were computed. In the case of compressional stress fields with subvertical orientation of the maximum extension, the axis of maximum compression σ1 were orientated from E-W to NW-SE, in south-eastern part of the Drahany Uplands up to NNW-SSE. In some cases, both the maximum compression axis and the maximum extension axis are orientated subhorizontally. The axis of σ1 was orientated NE-SW or E-W, axis of σ3 was orientated NW-SE or N-S. But at one site (the site 26) in the eastern part of the Nízký Jeseník area the inverse orientation of the σ1 axis and the σ3 axis were also computed. The extensional paleostress fields were computed only in the Nízký Jeseník area. The maximum extension axes were orientated approximately E-W (in wide range of orientations from NW-SE up to NE-SW). The orientations of the tensile fractures and the quartz veins measured in the eastern part of the Nízký Jeseník area do not agree to this result. The facts discussed in the article indicate the generally Variscan age of the found compressional stress fields. The younger extensional stress fields are probably late-Variscan and they can reflect the gravitational collapse of the Variscan orogene.