Origin and tectonic evolution of the Eastern Alps deduced from dating of detrital white Mica
- Author(s)
- F. Neubauer, G. Friedl, J. Genser, R. Handler, D. Mader, D. Schneider
- Abstract
Results of dating of detrital white mica using the conventional K-Ar, conventional Ar/ Ar multi-grain and laser-probe Ar/ Ar multi-grain and single-grain methods contribute significantly to the unraveling of the palaeogeographic origin and tectonic evolution of the Eastern Alps since Late Ordovician times. Dating of Upper Ordovician and Silurian successions of Austroalpine and Southalpine domains consistently demonstrato a Panafrican/Cadomian source of these successions, and therefore an origin along northern margins of Gondwana. The source region significantly changed in Lower to lowermost Upper Carboniferous Variscan flysch successions when Gondwana collided wilh Laurussia. The Lower Carboniferous flysch mostly contains Devonian detritus from units, which are largely unknown in the present erosional level of Eastern Alps. In contrast, Upper Carboniferous molesse, and Permian and Triassic rift and shelf successions nearly exclusively contain Variscan detritus of Carboniferous age. These Carboniferous ages of the molasse indicate that upper crustat levels with pre-Variscan age signatures have been largely removed prior to molasse deposition. Beside dominant Variscan and Permian ages, subondinate Early-Middle Jurassic ages of detrital white mica within the Florianikogel Formation, a Middle Jurassic flysch succession originating within the Meliata ocean, support the idea that Maliata oceanic seaway underwent Jurassic subduction, In contrast, only Variscan respectively Permian ages have been found up to now in the Lower Cretaceous Losenstein-, Branderfleck- and Rossfeld formations. These units are considered to represent a trench-fill in front of the accreting Austroalpine nappe stack, which partly underwent late Early Cretaceous metamorpic overprint, in the subsequent Upper Cretaceous Collapse basins (Gosau basins), K-Ar ages Indicate the presence of a variable proporton of Cretaceous-aged low-to medium-grade metamorphic units in the source regions. The Lower Cretaceous to Eocene Rhenodanubian Flysch basin is characterized by mainly Variscan ages, although source Upper Cretaceous levels are rich in Cretaceous-aged. white mica, similarly suggesting a source in the Austroalpine mappe complex. In tme North-Alpine Molesse basin, detritus with Variscan, Permian and Cretaceous ages is dominant and considered to derive from the Austroalpine mappe stack. Oligocene mica ages indicating exposure of Oligocene metamorphic rocks of Penninic units in the Tauern window were only found in the uppermost, Neogene stratigraphic levels of the the Molasse basin. Although close to the Tauern window, exclusively Cretacecus-aged detritus is found in the intramontane, fault-bounded Wagrath basin. This supports the idea of large (>40 km) sinisteal strike-slip displacement along the confining Zalzach-Enne fault.
- Organisation(s)
- Department of Lithospheric Research
- External organisation(s)
- Paris-Lodron Universität Salzburg
- Journal
- Austrian Journal of Earth Sciences
- Volume
- 100
- Pages
- 8-23
- No. of pages
- 16
- ISSN
- 0251-7493
- Publication date
- 01-2007
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105123 Stratigraphy, 105121 Sedimentology, 105106 Geodynamics, 105101 General geology
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/d82a986a-55aa-40c6-b223-641e0410ad64