The role of neotectonics in fluvial landscape development in the Western Mecsek Mountains and related foreland basins (SE Transdanubia, Hungary)

The paper presents an integrated application of geomorphological and geological methods to investigate the recent activity of a strike-slip fault system. Spatial analysis of Neogene and Quaternary sedimentary sequences through 3D basement and isopach maps based on surface geology, boreholes and sparse geophysical data revealed the evolutionary history of pull-apart basins linked to strike-slip faults. A model of a repeatedly branching and southward-shifting dislocation zone is proposed for the Cenozoic. Calculations from valley incision and sedimentation data resulted in estimations of minimum subsidence rates of 0.15–0.30 mm/y and 0.07–0.17 mm/y, respectively. Morphological analysis of the DEM including hillshade, aspect, slope and curvature calculations indicated a geological structure made up of several relatively small blocks showing contemporaneous, contrasting vertical movements. The continuity of Plio-Quaternary pediments and of palaeo-valleys has been broken by the neotectonic uplift or subsidence of some areas, these geomorphic features are thus indicators of vertical displacement of the blocks. River captures and rapid valley incisions refer to present-day basin subsidence. Several geomorphic features linked to tectonics – fault lines, ridges uplifted along these, triangular facets, valley deflections – support evidence suggesting activity of the fault system. The presence or absence of alluvial fans roughly correspond to more or less closed or open basins. These features together permitted the delineation of areas of ongoing uplift and subsidence. Neotectonic activity has been present during all periods since the Late Miocene, while the most important basin of the mountain foreland, the Pécs Basin, probably appeared as a morphological depression near the Middle–Late Pleistocene boundary.