Deformation partitioning during polyphase oblique convergence in the Karawanken Mountains, southeastern Alps

Abstract

The Karawanken Mountains of southeastern Austria straddle the Insubric Line, a major fault zone that corresponds to the Austroalpine-South Alpine border of the eastern Alps. They display polyphase structural patterns that resulted from deformation partitioning at shallow crustal levels. Following a poorly constrained late Cretaceous deformation history, Paleogene contraction produced NW—SE-trending fold—thrust structures and possibly related sinistral (?) cross faults. Miocene deformation produced both NW- and SE-directed thrust faults and NW-striking high-angle dextral cross faults which merged with or displaced the W-striking Insubric Line. Distributed dextral strike-slip displacements of the order of 30–40 km and thrust displacement of 4–5 km along the northern Karawanken front initiated subsidence of a small foreland basin north of the Karawanken Mountains. Recent regional deformation seems to be concentrated along cross-cutting NNW-striking dextral faults within a shifting system of seismogenic transfer faults that probably merge with the convergent South Alpine thrust front to the west. There are conspicuous parallels in the style of deformation along the Karawanken Mountains with that found along other seismogenic convergent strike-slip faults, such as those of southern California, New Zealand and Anatolia.