Late‐stage deformation in a collisional orogen (Western Alps): nappe refolding,back‐thrusting or normal faulting? |
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Authors: | Stefan Bucher Stefan M Schmid Romain Bousquet Bernhard Fügenschuh |
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Institution: | Department of Earth Sciences, Basel University, Bernoullistr. 32, CH-4056 Basel, Switzerland |
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Abstract: | ABSTRACT Nappe refolding, back-thrusting and normal faulting frequently cause severe late-stage overprinting of the architecture of an orogen. A combined investigation of nappe stack polarity, kinematics of shearing and metamorphic gradients in the Western Alps develops criteria for distinguishing between these three modes of late-stage deformation. This distinction is a prerequisite for any retro-deformation necessary for understanding the main tectonic and metamorphic evolution of collisional orogens. In the case of the Western Alps overprint was by mega-scale nappe refolding in the Oligocene. This implies exhumation of the HP-rocks prior to postnappe folding, i.e. during nappe stacking and by foreland-directed ascent within a subduction channel. |
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