Low temperature thermochronology in the Eastern Alps: Implications for structural and topographic evolution

Abstract

According to new apatite fission track, zircon- and apatite (U–Th)/He data, we constrain the near-surface history of the southeastern Tauern Window and adjacent Austrolapine units. The multi-system thermochronological data demonstrate that age-elevation correlations may lead to false implications about exhumation and cooling in the upper crust. We suggest that isothermal warping in the Penninic units that are in the position of a footwall, is due to uplift, erosion and the buildup of topography. Additionally we propose that exhumation rates in the Penninic units did not increase during the Middle Miocene, thus during the time of lateral extrusion. In contrast, exhumation rates of the Austroalpine hangingwall did increase from the Paleogene to the Neogene and the isotherms in this unit were not warped. The new zircon (U–Th)/He ages as well as zircon fission track ages from the literature document a Middle Miocene exhumation pulse which correlates with a period of enhanced sediment accumulation during that time. However, enhanced sedimentation- and exhumation rates at the Miocene/Pliocene boundary, as observed in the Western- and Central Alps, cannot be observed in the Eastern Alps. This contradicts a climatic trigger for surface uplift, and makes a tectonic trigger and/or deep-seated mechanism more obvious to explain surface uplift in the Eastern Alps.In combination with already published geochronological ages, our new data demonstrate Oligocene to Late Miocene fault activity along the Möll valley fault that constitutes a major shear zone in the Eastern Alps. In this context we suggest a geometrical and temporal relationship of the Katschberg-, Polinik–Möll valley- and Mur–Mürz faults that define the extruding wedge in the eastern part of the Eastern Alps. Equal deformation- and fission track cooling ages along the Katschberg–Brenner- and Simplon normal faults demonstrate overall Middle Miocene extension in the whole alpine arc.

Exhumation mechanisms of the Tauern Window (Eastern Alps) inferred from apatite and zircon fission track thermochronology

“…Reduced variance corresponding to each exhumation interval is shown in Figure 3 of the supporting information. The models are obtained by inversion of apatite fission track ages [this study; Dunkl et al ., ; Fügenschuh et al ., ; Mancktelow et al ., ; Most , ; Pomella , ; Steenken et al ., ; Stöckhert et al ., ; Viola et al ., ; Wölfler et al ., ], zircon fission track ages [ Grundmann and Morteani , ; Staufenberg , ; Coyle , ; Hejl , ; Mancktelow et al ., ; Most , ; Viola et al ., ; Steenken et al ., ; Foeken et al ., ; Wölfer et al ., , ; Pomella , ; Di Fiore , ], and K/Ar ages [ Luth and Willingshofer , ]. Black line represents the boundary of the Tauern Window.…”

“…Our new data and all available zircon and apatite fission track ages from the Tauern Window and surrounding Austroalpine areas [Grundmann and Morteani, 1985;Staufenberg, 1987;Coyle, 1994;Fügenschuh et al, 1997;Mancktelow et al, 2001;Viola et al, 2001;Steenken et al, 2002;Dunkl et al, 2003;Most, 2003;Foeken et al, 2007;Pomella, 2010;Wölfler et al, 2008Wölfler et al, , 2012Wölfler et al, , 2015Di Fiore, 2013] are compiled and interpolated using a natural neighbor algorithm tool of Esri ArcMap 10 ™ geographic information system (GIS) software (Figures 8b and 9b). Extended cells for the interpolation are of 500 m, and analytical errors are not taken into account.…”

Orogen-parallel extension and topographic gradients east of the Tauern window: a possible indication of intra-orogenic raft tectonics?

“…800 m have been eroded from the Schladming crystalline basement since the end of the Miocene. Wölfler et al (2008Wölfler et al ( , 2011Wölfler et al ( , 2012 suggest that exhumation constrained by apatite fission track ages of the Eastern Alps correlates well with increased sedimentation in the Middle Miocene. The estimated erosion rate of 0.04 km/Ma is in agreement with the AFT ages of Hejl (1997) and Reinecker (2000).…”

“…Published thermochronological data form the basis of this study (Stauffenberg, 1987;Hejl, 1997Hejl, , 1998Reinecker, 2000;Frisch et al, 2001;Foeken, 2007;Wölfler et al, 2008Wölfler et al, , 2011Wölfler et al, , 2012. In recent decades, a variety of thermochronological methods with increasing complexity was used to infer exhumation rates in the context of topographic gradients.…”

“…We plotted all published AFT, AHe and ZHe data from the Penninic basement of the Tauern window (Staufenberg 1987;Foeken et al 2007;Wölfler et al 2011Wölfler et al , 2012. The data refers to the Sonnblick Dome (SD) south of the Möll Valley fault and the Hochalm Dome (HD) north thereof (Fig.…”