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Int J Earth Sci. 2017;106(5):1557-1580. doi: 10.1007/s00531-016-1367-3. Epub 2016 Jul 13.

Postcollisional cooling history of the Eastern and Southern Alps and its linkage to Adria indentation.

Author information

1
1Department of Geography and Geology, University of Salzburg, Hellbrunner Str. 34, 5020 Salzburg, Austria.
2
2Geological Institute, ETH Zürich, Sonneggstrasse 5, 8092 Zurich, Switzerland.
3
3Department of Earth and Planetary Sciences, University of California, Berkeley, Berkeley, CA 94720 USA.
4
4Institute for Geochemistry and Petrology, ETH Zürich, Clausiusstrasse 25, 8092 Zurich, Switzerland.
5
5Geoscience Center, University of Göttingen, Goldschmidtstrasse 3, 37077 Göttingen, Germany.
6
6Department of Geosciences, University of Padua, Via G. Gradenigo 6, 35131 Padua, Italy.
7
7School of Geography, Environment and Earth Sciences, Victoria University of Wellington, PO Box 600, Wellington, 6012 New Zealand.

Abstract

Indentation of rigid blocks into rheologically weak orogens is generally associated with spatiotemporally variable vertical and lateral block extrusion. The European Eastern and Southern Alps are a prime example of microplate indentation, where most of the deformation was accommodated north of the crustal indenter within the Tauern Window. However, outside of this window only the broad late-stage exhumation pattern of the indented units as well as of the indenter itself is known. In this study we refine the exhumational pattern with new (U-Th-Sm)/He and fission-track thermochronology data on apatite from the Karawanken Mountains adjacent to the eastern Periadriatic fault and from the central-eastern Southern Alps. Apatite (U-Th-Sm)/He ages from the Karawanken Mountains range between 12 and 5 Ma and indicate an episode of fault-related exhumation leading to the formation of a positive flower structure and an associated peripheral foreland basin. In the Southern Alps, apatite (U-Th-Sm)/He and fission-track data combined with previous data also indicate a pulse of mainly Late Miocene exhumation, which was maximized along thrust systems, with highly differential amounts of displacement along individual structures. Our data contribute to mounting evidence for widespread Late Miocene tectonic activity, which followed a phase of major exhumation during strain localization in the Tauern Window. We attribute this exhumational phase and more distributed deformation during Adriatic indentation to a major change in boundary conditions operating on the orogen, likely due to a shift from a decoupled to a coupled system, possibly enhanced by a shift in convergence direction.

KEYWORDS:

Adria indentation; Exhumation; Low-temperature thermochronology; Southern and Eastern Alps

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