DEM based morphotectonical analysis of the Kisgyőr Basin (Bükk Mts – Hungary)

The south-eastern part of the Bükk Mountains and the eastern side of its foothill, the Bükkalja are among the less explored regions of Hungary. Based on our examinations on the field, we found that the asymmetrical valley sections, the tipped escarpments and the formation of the Kisgyőr Basin cannot be explained by the differences in the rock quality. The asymmetrical shape of these landforms and the stream captures identified in the research area indicate significant structural geological changes. In our work, we proved the asymmetry in the topography by performing swath profile analysis, and we also examined the elevation data of the areas covered by the welded ignimbrites of the Tar Dacite Tuff Formation. The results confirmed our field observations. We found that, contrary to the results of previous research, the geological structural processes played a fundamental role in the formation of the Kisgyőr Basin and its surroundings.

Rock mass rating in Bükk Mts., N Hungary based on petrophysical parameters and parting conditions

In the region of Bánkút and Ómassa, Bükk Mountains the strength of the rocks of 29 outcrops was studied based on Rock Mass Rating (RMR). Strength of the rock masses showed no correlation with the material of the Formations they exposed, however, correlation between the orientation of valleys and ridges and the location of the most deformed rocks and thus that of the rock masses with poorest qualification could be observed.

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

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 synsedimentary 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.

In situ gamma ray survey for geological mapping of Kmetasomatized metavolcanics at Bükkszentkereszt, Bükk Mts, Hungary

The Middle-Upper Triassic Bagolyhegy Metarhyolite Formation of the Bükk Mts. (Hungary) hosts silicified bodies with high potassic feldspar content formed by Kmetasomatism. The rocks underwent a multistage deformation history including syn- and postmetamorphic folding and faulting. As the outcrop area is covered by soil and debris with some exposed silicified cliffs only, and potassium content is a characteristic feature of the metasomatized rocks, geological mapping was supported by a spectral gamma ray survey with a scintillation detector of NaI(Tl) crystal. A thunderstorm felling the beech forest made the soil horizon B also accessible in several pits, providing the opportunity to make measurements on the weathered debris instead of the topsoil (horizon A). Measurements in different arrangements were designed to test the effects of measuring time, measuring geometry and soil horizon. Our results show that concentration values obtained on the debris with a 2 min measuring time can be compared with those measured on exposed rock surfaces, producing a more reliable geological map than measurements on the topsoil with randomly variable K depletion. Pit geometry effects can be eliminated by the K/(eU+eTh) ratio. This results in a more realistic K distribution map if neither U nor Th enrichments are present. The survey successfully delineated the unexposed outcrop of K-enriched rocks on the survey area.