Portal de Periódicos da CAPES

Inherited tectonic structures controlling the deformation style: an example from the Helvetic nappes of the Eastern Alps

2014; Springer Nature; Volume: 107; Issue: 2-3 Linguagem: Inglês

10.1007/s00015-014-0167-7

1661-8734

Michael Zerlauth, Hugo Ortner, Hannah Pomella, O. Adrian Pfiffner, Bernhard Fügenschuh,

Hydrocarbon exploration and reservoir analysis

Based upon tectonic as well as facies arguments, two different Helvetic nappes can be distinguished in western Austria (Vorarlberg) and in southwestern Germany (Upper Allgäu): the Hohenems nappe and the overlying Vorarlberg Säntis nappe. Both encompass Middle Jurassic to Eocene strata deposited on the internal to external shelf of the southward deepening European margin of the Eurasian plate. Synsedimentary normal faults caused changes in thickness and facies of the various strata, which play a crucial role in deformation behavior. Arcuate fold axes in map view and an almost 3 km thick sequence of stacked Middle Jurassic shales and sandstones drilled below a Jurassic anticlinorium in the southern part of the Bregenzerwald are thought to be indicative of an inverted Jurassic basin. Inversion occurred during the Cenozoic Alpine nappe formation along synsedimentary normal faults, reactivated as ramps and tear faults. A lateral ramp, segmented by tear faults, running along the Iller Valley, and a supposed lateral ramp in the subsurface of the Rhine Valley mark the extension of the inverted former basin. Fault deformation style changes across the Rhine Valley. East of it, i.e. in Vorarlberg, the Vorarlberg Säntis nappe comprises a coherent succession of Jurassic and Cretaceous strata detached along Middle Jurassic sediments. In the west, on the other hand, Cretaceous strata of the Swiss Säntis nappe were largely detached from their Jurassic substrate (Gonzen-Walenstadt imbricates) along the Säntis thrust. This allows to correlate the Helvetic nappe stack of eastern Switzerland, comprising the Swiss Säntis nappe (together with the Gonzen-Walenstadt imbricates) and the underlying Mürtschen nappe, with the Vorarlberg Säntis nappe and the Hohenems nappe of Austria.