International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

STRUCTURAL HISTORY OF THE PORVA BASIN IN THE NORTHERN BAKONY MTS (WESTERN HUNGARY): IMPLICATIONS FOR THE MESOZOIC AND TERTIARY TECTONIC EVOLUTION OF THE TRANSDANUBIAN RANGE AND PANNONIAN BASIN

Pages: 183 - 190

Authors: ADA KISS, BALAZS GELLERT, LASZLO FODOR

Abstract: The authors made geological mapping and microtectonic measurements in the Northern Bakony Mts., around the Porva Basin. Using structural observations, a new structural-geological map was made for this area. Four tectonic phases were separated by the analysis of stress field. Map-scale neptunian dikes represent the Jurassic rifting episode. For this phase NNE-SSW tension was estimated. NW-SE compression of Albian (?) age resulted in gently dipping reverse and conjugate strike-slip faults. In the Ottnangian-Sarmatian (18.5–11 Ma) a strike-slip type stress field with NNW-SSE compression developed. This phase formed mainly NW-SE striking dextral and conjugate shorter sinistral strike-slip faults. NW-SE striking half-grabens formed along strike-slip or oblique-slip faults. Motion resulted in post-sedimentary tilting of the Eocene-Oligocene sequences toward the master faults. A late Miocene extensional phase with WNW-ESE tensional directions was also determined. During this phase the earlier half-grabens were reactivated, although with slightly different slip on boundary faults. Some of the young half-grabens are connected by transfer faults, which had a strike-slip character. Ottnangian-Sarmatian strike-slip faults occurred during the rifting phase of the Pannonian Basin, their main activity was coeval with important stretching in the northeastern Pannonian Basin. These relatively local strike-slip faults could accommodate differential extension between the northern and southern Pannonian Basin. On the other hand, the newly recognized Late Miocene tensional phase indicate, that the post-rift evolution of the Pannonian Basin was associated with considerable crustal extension.

Keywords: Cretaceous, Miocene, Pannonian Basin, Bakony Mts, structural geology, strike-slip fault, half-graben, stress field

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