New insights on Suretta nappe structure and lithostratigraphy revealed by high-resolution geological survey of Val di Lei (Central Alps, Italy)

This contribution presents a 1:10.000 scale geological map of the Val di Lei basin (Italian Central Alps), produced within the framework of the Italian National Geological Mapping Project (CARG). The area mainly exposes rocks of the Suretta nappe (Middle Penninic) and minor portions of the Avers nappe (Upper Penninic). The Suretta nappe comprises a polymetamorphic basement, Carboniferous–Permian metaplutonites, and a Permian–Mesozoic metasedimentary cover. The structural framework reflects a polyphase Alpine deformation superimposed on relict pre-Alpine features. New field data refine the lithostratigraphy and the structural architecture of the Suretta nappe, providing new constraints on its polycyclic metamorphic evolution. Eclogite- and amphibolite-facies assemblages, together with localized evidence of partial melting, attest to a pre-Alpine evolution of the basement. These observations contribute to assessing the extent of Alpine overprinting on older metamorphic assemblages and may provide new constraints on the pre-Alpine evolution of basement units in this sector of the Central Alps.