Kinematic evolution of the western Tethyan realm derived from paleomagnetic and geologic data

Wolfgang Thöny

Research output: ThesisDoctoral Thesis

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New paleomagnetic results from 140 sites in the Eastern and Southern Alps are presented. A first phase of clockwise rotation is active between Early Rupelian to Late Rupelian times (32-29Ma) affecting the Eastern Alps (EA), Southern Alps (SA) and the Southern Alpine Foreland Basin (SAFB). This rotation can be related to the thrusting of NCA, Flysch and Helvetic units and was possibly driven by a retreat of the European lower lithosphere. A second phase of clockwise rotation, still related to slab retreat of the European lower lithosphere, is dated to Middle to Latest Chattian (25-23Ma) and incorporates the Subalpine Molasse and the units of the Penninic Tauern window. The youngest, counterclockwise vertical axis rotation is postdating the folding of Messinian Montello conglomerates of the northern Venetian Alps and consequently must be younger than 5Ma. This rotation is observed in the Subalpine Molasse, EA, SA, SAFB and the northern parts of Adria. To the north, the rotating units are limited by the frontal Alpine thrusts as sites with synchronous magnetization ages north of the Alpine front (tilted Molasse, autochthonous Molasse) do not indicate any vertical axis rotation. The young counterclockwise rotation is probably related to the opening (5-3Ma) of the Tyrrhenian Sea/ Vavilov basin and the resulting young rotation of Adria. Data from Penninic nappes from previous studies indicate 30° of counterclockwise rotation relative to the Late Cretaceous/ Eocene reference direction. Most probably this rotation is caused by the subduction of the Penninic Ocean and was active post Middle Eocene. Comparison with the data from the Penninic units identified an additional counterclockwise rotation of 30° of Paleogene, post Early Eocene age in the Lechtal nappe of the western Northern Calcareous Alps (NCA), the Tirolic units and the Southern Alps, but this is not known in the Bajuvaric units of the central NCA east of the Inn valley according to the available literature. After restoring the Miocene to Eocene vertical axis rotations that affected NCA and Southern Alps Jurassic to Cretaceous paleomagnetic data are showing approximately N-directed declinations. Obviously during opening of the Central Atlantic and the counterclockwise rotation of Africa the Eastern/Southern Alps did not rotate and were probably separated from the rotating units by an approximately E-W striking shear zone.
Translated title of the contributionAnalyse der kinematischen Entwicklung der westlichen Tethys unter Verwendung paläomagnetischer sowie geologischer Daten
Original languageEnglish
  • Scholger, Robert, Assessor A (internal)
  • Ortner, Hugo, Co-Supervisor (external), External person
Publication statusPublished - 2008

Bibliographical note

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  • western Tethyan
  • paleomagnetism
  • geology
  • Austria
  • Eastern Alps
  • Southern Alps

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