Anatomy and tectono-sedimentary evolution of a rift-related detachment system: The example of the Err detachment (central Alps, SE Switzerland)

The discovery of hyperextended crust in present-day magma-poor distal rifted margins has major implications for the development of rift concepts. Indeed, the occurrence of low-angle detachment faulting changes the structural style and modifies the classical architecture of rifted margins, often represented by tilted blocks and bounded by high-angle normal faults. At present, little is known about the ways in which detachment systems form in distal margins through time and space and the way in which they control the formation of supradetachment rift basins. In this paper, we discuss a Jurassic rift-related detachment system of the fossil Adriatic distal rifted margin, today exposed in the Lower Austroalpine Err nappe in SE Switzerland. A palinspastic restoration of the Alpine units places the three-dimensional postrift architecture of this detachment system over more than 200 km(2) and 34 km in transport direction. Based on the description of a preserved supradetachment basin, we can show that the synrift sedimentary evolution records the formation of supradetachment extensional allochthons and the exhumation of basement rocks. Using this well-exposed example, we will show that detachment systems are intimately related to the overall tectono-sedimentary evolution of the most distal parts of the Adriatic rifted margin and possibly other Atlantic-type magma-poor hyperextended rifted margins.