Lateral extrusion in the Eastern Alps revisited: Refining the model by thermochronological, sedimentary, and seismic data

Abstract

[1] This study comprises a reassessment of the classical model of lateral extrusion in the Eastern Alps by using recently published geochronological data, sedimentary ages from intramontane basins, ages and distribution of magmatic rocks, and information from seismic profiles. Extrusion-related faulting continuously propagated from the western toward the central eastern part of the Eastern Alps during Oligocene to Middle Miocene times. This is confined by oblique convergence between the Adriatic and European plates. During Middle Miocene times, extrusion became not only lateral in terms of parallel to the trend of the Eastern Alps, but was characterized by a displacement vector at a high angle to the strike of the orogen. This resulted in the exhumation of the Schladming and Pohorje blocks that were exhumed within extensional bridges at the northern and southern terminations of the Pöls-Lavanttal fault system, respectively. From Middle Miocene to recent times, extrusion was controlled by overall extension between the Dinaric and Carpathian subduction zones. The influence of north directed compression triggered by the northward moving Adriatic plate diminished, and the influence of the retreating Carpathian subduction zone increased. This gave rise to Miocene volcanism that is exclusively found east of the Dinaric subduction zone. We therefore consider that lateral extrusion in the Eastern Alps can be subdivided into distinct tectonic phases, with less pronounced eastward extension-related displacement between Late Oligocene and Middle Miocene times. As soon as the Eastern Alps passed the Dinaric subduction zone, the entire domain became highly extensive.

Cretaceous to Miocene cooling of Austroalpine units southeast of the Tauern Window (Eastern Alps) constrained by multi-system thermochronometry

“…Hoke (1990); (6) Dunkl et al (2003); (7) Wölfler et al (2008); (8) Staufenberg (1987); (9) Lambert (1970). For closure temperature ranges we adopted the following values: K/Ar muscovite: ~430-375°C (Hames and Bowring, 1994;Kirschner et al, 1996); Ar/Ar muscovite: ~450-350°C (Hames and Bowring, 1994;Kirschner et al, 1996;Lips et al, 1996;Harrison et al, 2009); Ar/Ar biotite: 400-300°C (Grove and Harrison, 1996;Villa, 1998); zircon fission track: 300-200°C (Wagner and van den haute, 1992); apatite fission track: 120-60°C (Green et al, 1986 Ma, respectively (Kralik et al, 1987 Scharf et al, 2013;Wölfler et al, 2008Wölfler et al, , 2011Wölfler et al, , 2012 Selverstone, 1988;Genser and Neubauer, 1989;Fügen-schuh et al, 1997;Scharf et al, 2013;Schmid et al, 2013). The southern boundary of the Eastern Alps is represented by the Periadriatic fault system, separating the Austroalpine and Southalpine units (Fig.…”

“…During the lateral tectonic extrusion of the Eastern Alps in Oligocene-Miocene times (e.g. Ratschbacher et al, 1991a, b;Wölfler et al, 2011) the footwall Penninic units exposed in the Tauern Window (Figs. 2, 3), were tectonically exhumed from below the Austroalpine hanging wall (Frisch et al, 1998(Frisch et al, , 2000.…”

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.…”