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The continental crust involved in the Alpine orogeny was largely shaped by Paleozoic tectono‐metamorphic and igneous events during oblique collision between Gondwana and Laurussia. In order to shed light on the pre‐Alpine basement puzzle disrupted and reamalgamated during the Tethyan rifting and the Alpine orogeny, we provide sensitive high‐resolution ion microprobe U‐Pb zircon and geochemical whole rock data from selected basement units of the Grand St Bernard‐Briançonnais nappe system in the Western Alps and from the Penninic and Lower Austroalpine units in the Central Alps. Zircon U‐Pb ages, ranging from 459.0 ± 2.3 Ma to 279.1 ± 1.1 Ma, provide evidence of a complex evolution along the northern margin of Gondwana including Ordovician transtension, Devonian subduction, and Carboniferous‐to‐Permian tectonic reorganization. Original zircon U‐Pb ages of 371 ± 0.9 Ma and 369.3 ± 1.5 Ma, from calc‐alkaline granitoids of the Grand Nomenon and Gneiss del Monte Canale units, provide the first compelling evidence of Late Devonian orogenic magmatism in the Alps. We propose that rocks belonging to these units were originally part of the Moldanubian domain and were displaced toward the SW by Late Carboniferous strike‐slip faulting. The resulting assemblage of basement units was disrupted by Permian tectonics and by Mesozoic opening of the Alpine Tethys. Remnants of the Moldanubian domain became either part of the European paleomargin (Grand Nomenon unit) or part of the Adriatic paleomargin (Gneiss del Monte Canale unit), to be finally accreted into the Alpine orogenic wedge during the Cenozoic.

The geological map of the Saint-Marcel valley at the scale of 1:20,000 illustrates the tectonic setting of metaophiolites from the southern Aosta Valley, in the Italian side of the Western Alpine belt. The map highlights the sharp contact between the metaophiolitic basement and its metasedimentary cover, which mainly consists of quartzites, marbles, and calcschists. In spite of the Alpine tectonics, this contact is regarded as deriving from the original oceanic crust/sediments interface. Metaophiolites mostly consist of metabasalts hosting Fe-Cu sulphide mineralisations, characterised by high-pressure metamorphic imprint. These rocks likely represent the shallowest portion of the Tethyan oceanic lithosphere created near the axis of the slow-spreading ridge where hydrothermal fluid circulation was active. Selected key-sections through metasediments reveal a consistent internal lithostratigraphy, in spite of the pervasive metamorphic and tectonic reworking acting during the Alpine evolution. Metasediments reflect various sedimentation episodes starting from pelagic and proximal settings to the onset of the orogenic stage. The Saint-Marcel valley metasediments thus reflect a changing in the sedimentation environments through time and space during the overall geologic evolution. ARTICLE HISTORY

We present a 1:30,000 geological map resulting from detailed geostructural surveys carried out along the Italian segment of the design corridor for the Brenner Pass railway base tunnel (BBT), extending from Fortezza (Italy) to Innsbruck (Austria). The map covers the southern part of the Austroalpine-Penninic collisional wedge, the Periadriatic Fault System, associated Oligocene igneous bodies (Periadriatic magmatism) and part of the Southalpine basement. The Penninic Zone in the western Tauern Window is represented by the double domal structure of the Europe-derived Tux and Venediger-Zillertal basement and cover nappe system, capped by the ophiolitic Glockner nappe. The overlying Austroalpine nappe system is here represented by the polymetamorphic Merano-Mules basement and minor cover sheets. The Southern Alps domain includes the Bressanone Granite and pre-granite quartz-phyllites. Four Alpine ductile deformation phases have been recognized, followed by ductile-brittle shear zones, and finally brittle deformations along faults with extensional and strike-slip kinematics. The Quaternary is characterized by glacial deposits, large gravitational mass movements and landslides.

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