The transition zone of the Eastern Alps to the Pannonian Basin provides one of the best sources of information on landscape evolution of the Eastern Alpine mountain range. The region was non-glaciated during the entire Pleistocene. Thus, direct influence of glacial carving as a landscape forming process can be excluded and relics of landforms are preserved that date back to at least the Late Neogene. In this study, we provide a correlation between various planation surfaces across the orogen-basin transition. In particular, we use stream terraces, planation surfaces and cave levels that cover a vertical spread of some 700 m. Our correlation is used to show that both sides of the transition zone uplifted together starting at least about 5 Ma ago. For our correlation we use recently published terrestrial cosmogenic nuclide (TCN) burial ages from cave sediments, new optically stimulated luminescence (OSL) ages of a stream terrace and U–Th ages from speleothems. Minimum age constraints of cave levels from burial ages of cave sediments covering the last ~ 4 Ma are used to place age constraints on surface features by parallelizing cave levels with planation surfaces. The OSL results for the top section of the type locality of the Helfbrunn terrace suggest an Early Würm development (80.5 ± 3.7 to 68.7 ± 4.0 ka). The terrace origin as a penultimate gravel deposit (in classical Alpine terminology Riss) is therefore questioned. U-series speleothem ages from caves nearby indicate formation during Marine Isotope Stages (MIS) 5c and 5a which are both interstadial warm periods. As OSL ages from the terrace also show a time of deposition during MIS 5a ending at the MIS 5/4 transition, this supports the idea of temperate climatic conditions at the time of deposition. In general, tectonic activity is interpreted to be the main driving force for the formation and evolution of these landforms, whilst climate change is suggested to be of minor importance. Obvious hiatuses in Miocene to Pleistocene sediments are related to ongoing erosion and re-excavation of an uplifting and rejuvenating landscape.
The Meliata nappe of the Western Carpathian orogen is comprised of Triassic deep-sea metasedimentary rocks and fragments of blueschist-bearing ophiolite. These were structurally emplaced onto Permian/Triassic shelf sequences and its Variscan basement. The nappe records a succession of deformational events which formed under decreasing pressure conditions. Subduction-related burial and resulting blueschist metamorphism is dated by 40 Ar/ 39 Ar plateau ages recorded by four phengitic muscovite concentrates (160-150 Ma). These crystallized during ductile deformation characterized by predominantly coaxial NW-SE stretching. The structures were overprinted by semiductile, nonpenetrative fabric elements which formed under greenschist facies conditions and contemporaneously with fabrics which developed in footwall tectonic units. Kinematic indicators record top north to NW shear during Middle Cretaceous loading of the Meliata unit onto the Inner Carpathian nappe complex recorded by a 40 Ar/ 39 Ar whole rock phyllite age of 105.8 + 1.5 Ma. A subsequent southeastern sense of shear is interpreted to have resulted from extension during Late Cretaceous uplift along hinterland margins of the tectonic wedge. The Meliata unit is part of a major Late Jurassic/Early Cretaceous suture which initially extended from the Alps to the Hellenides. It has been subsequently disrupted as a result of later strike-slip faulting following Tertiary collision of the Cretaceous orogen, and was transported onto extra-Alpine European units.
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