The importance of tangential motion in the Central Alps: Kinematic analysis and Rb Sr dating of mylonitic rocks from the Pennine nappes in the eastern Central Alps

We discuss the important role of tangential stretching in Central Alps highlighting that are a truly three-dimensional orogen. A review pressure-temperature (P-T) conditions allows us to define three major breaks metamorphic pressure (P-breaks) across nappe pile. constrain kinematics mylonites associated with these P-breaks and report eight new RbSr multi-mineral isochrons age mylonites. Kinematic data geochronology indicate timing top-SE normal shearing Avers-Turba mylonite zone (?45–34 Ma; P-break1) distributed top-E (>35–30 Ma) above (ultra)high-P Adula distal, thinned European margin (P-breaks 2 3). The ages from both sets grading into each other at about 35–34 Ma. All appear postdate high-P metamorphism Pennine nappes but are, part, coeval predate underlying distal (Helvetic) margin. oldest 42.3 ± 2.5 Ma (2? uncertainties) dates waning stage mylonitization indicates started operate ?45 Ma, predated exhumation by ~10 suggest motion overlapped backfolding Schams an extrusion wedge. When this process started, was still being underthrust/underplated. for contemporaneous thrusting on top distinctly lower-P Helvetic nappes. thrust onto non-high-P necessary reduction its overburden largely accomplished faulting nappe, possibly ongoing shearing. occurred during lithospheric shortening. Our considerable (out-of-plane) movements overall top-N/NW propagation have implications current tectonic models Alps.