Jura-Beckenentwicklung in der nördlichen Saalachzone (Unken, Salzburg, Österreich)

Research output: ThesisMaster's ThesisResearch

Organisational units

Abstract

Aim of this work was the reinvestigation of the controversially discussed northern Saalach Zone as part of the far-travelled Hallstatt Mélange with its complex tectonic setting. The Saalach Zone is bordered by the Unken syncline to the west and the Berchtesgaden Alps to the east. Thereby, the Unken syncline forms the tectonic footwall and the Berchtesgaden Alps the hanging wall. This nappe stack is proposed to be created in the Early Cretaceous. Due to geological mapping, biostratigraphic dating and analysis of the microfacies, following results are presented: The interpretation of an Early Cretaceous thrusting above the Rossfeld Formation by Triassic/Jurassic rocks cannot be confirmed. The footwall is represented by parautochthonous Dachstein limestone (Late Triassic) and red nodular limestones of the Adnet- and Klaus Formations (Early to Middle Jurassic). This succession was disintegrated by normal faults in northwestward directions. In late Middle Jurassic times the depositional environment changed and a new deep-water basin was established, containing at the base reworked material from the underlying parautochthonous basement. The lower part of the basin fill is represented by a red limestone breccia followed by a Dachstein limestone megabreccia, showing a coarsening upward trend. The sequence continues with red and black radiolarites, which contains exotic slides and mass flows derived from the proximal Hallstatt zone (Zlambach facies). A coarsening upward trend is also clearly identified here. This succession shows the evolution of a deep-water trench (Lammer Basin) in front of an advancing nappe stack. In Late Jurassic times the Sandlingalm Hallstatt Mélange (distal Hallstatt Limestones) was overthrusted with the Haselgebirgs Mélange at its base from SE onto the Lammer Basin. After this tectonic event a carbonate platform prograded over the older nappe stack, in younger times showing also northwards thrusting. This evolution suggests a far southward palaeogeographic position of the study area in the Late Jurassic. The actual position is the result of younger tectonic movements, characterized by pull-apart structures, block rotations and NW-SE directed sinistral strike-slip movements. Due to these results a potential HC system is hypothesized. Jurassic, organic-rich sediments (manganese shales, radiolarites and cherty limestones) represent source rocks, dolomites and limestones reservoir rocks. In addition, radiolarites and cherty limestones can be used as unconventional reservoirs. The evaporitic Haselgebirgs Mélange acts as seal as well as parts of the eroded cover. Due to the complex, polyphase tectonics, traps can be structural or stratigraphic.

Details

Translated title of the contributionJurassic basin evolution of the northern Saalach Zone (Unken, Salzburg, Austria)
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
Award date16 Dec 2011
Publication statusPublished - 2011