Alpine and pre-Alpine tectonics in the Central Orobic Alps (Southern Alps)

A sequence of regional deformation episodes is described in the Permian cover and in the metamorphic basement of a portion of the Southern Alps, southeast of Sondrio (Valtellina). The earliest episode is contemporaneous with low to medium grade metamorphism in the basement; the second episode occurs during low temperature greenschist-facies retrogradation in the basement; these two synmetamorphic regional deformation episodes in the basement are pre-Alpine (probably of Variscan age) and predate the deposition of Permian sediments. Cover and basement are deformed together during a third tectonic episode of post-Triassic age, unrelated to regional metamorphic reactivation, and associated with nappe emplacement and regional folding, that took place at shallow levels of the Southalpine margin during Alpine time.