International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

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40Ar/39Ar dating of detrital white mica of Upper Paleozoic sandstones in the Carnic Alps (Austria): implications for provenance and tectonic setting

Published: Apr 2007

Pages: 133 - 144

Authors: DIETER MADER, FRANZ NEUBAUER, ROBERT HANDLER

Abstract: New information on the geodynamic development and the provenance for Carboniferous to Permian successions exposed within the Carnic Alps is supplied by an integrated approach of microprobe analysis and 40Ar/39Ar dating of detrital white mica. 40Ar/39Ar analyses of detrital white mica concentrates (4–10 grains) from syn- and post-orogenic Mississippian to Late Permian successions display an apparently uniform population and time lag of the isotopic ages with respect to the stratigraphic age of their host rock: early Variscan ages (373–396 Ma) are reported within syn-orogenic Visean-Namurian turbiditic sandstones, Variscan ages (333–309 Ma) in post-orogenic Pennsylvanian and Permian terrestrial and shallow marine sandstones. Detrital white micas from Mississippian syn-orogenic sandstones indicate an intermediate time interval between the cooling of the source rock and deposition, typical for compressional accretionary wedge settings. Furthermore, these ages argue for a Middle Devonian tectonothermal event in the hinterland. Detrital white micas from Pennsylvanian sandstones indicate a very narrow time lag between post-Variscan cooling of the source region and the depositional age. This points to a rapid exhumation of rocks in the source region from mid-crustal levels prior to the deposition of these sediments.

Keywords: Late Paleozoic, Southern Alps, Ar-Ar-dating, provenance, sandstones, detrital mica

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