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

Cenozoic structural evolution of the southwestern Bükk Mts. and the southern part of the Darnó Deformation Belt (NE Hungary)

Pages: 83 - 104

Authors: ATTILA PETRIK, BARBARA BEKE, LÁSZLÓ FODOR, RÉKA LUKÁCS

Abstract: Extensive structural field observations and seismic interpretation allowed us to delineate 7 deformation phases in the study area for the Cenozoic period. Phase D1 indicates NW—SE compression and perpendicular extension in the Late Oligocene—early Eggenburgian and it was responsible for the development of a wedge-shaped Paleogene sequence in front of north-westward propagating blind reverse faults. D2 is represented by E—W compression and perpendicular extension in the middle Eggenburgian—early Ottnangian. The D1 and D2 phases resulted in the erosion of Paleogene suites on elevated highs. Phase D2 was followed by a counterclockwise rotation, described in earlier publications. When considering the age of sediments deformed by the syn-sedimentary D3 deformation and preliminary geochronological ages of deformed volcanites the time of the first CCW rotation can be shifted slightly younger (~17—16.5 Ma) than previously thought (18.5—17.5 Ma). Another consequence of our new timing is that the extrusional tectonics of the ALCAPA unit, the D2 local phase, could also terminate somewhat later by 1 Myr. D4 shows NE—SW extension in the late Karpatian—Early Badenian creating NW—SE trending normal faults which connected the major NNE—SSW trending sinistral faults. The D5 and D6 phases are late syn-rift deformations indicating E—W extension and NW—SE extension, respectively. D5 indicates syn-sedimentary deformation in the Middle Badenian—early Sarmatian and caused the syn-sedimentary thickening of mid-Miocene suites along NNE—SSW trending transtensional faults. D5 postdates the second CCW rotation which can be bracketed between ~16—15 Ma. This timing is somewhat older than previously considered and is based on new geochronological dates of pyroclastite rocks which were not deformed by this phase. D6 was responsible for further deepening of half-grabens during the Sarmatian. D7 is post-tilt NNW—SSE extension and induced the deposition of the 700 m thick Pannonian wedge between 11.6—8.92 Ma in the southern part of the study area.

Keywords: Bükk Mts., Cenozoic, fault pattern, stress field, seismic profile, deformation band

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