Fig. 14

Interpretation of the origin of the southern Cottian Alps metamorphic units at the expense of the subducted Briançonnais distal margin. The half-arrows feature the locus of detachment where each unit was sampled. Acronyms as follows: A: Acceglio-Longet; BI: Brossasco-Isasca; CC: Ceillac-Chiappera; MA: Marinet; MV: Monviso complex.RS: Rocca Solei; SP: Sanfront-Pinerolo; SL: Schistes lustrés (Queyras nappe); VG: Val Grana; VM-S: Val Maira-Sampeyre; The subduction channel is left “open” (white) for clarity; it is supposed to contain a mélange of Schistes lustrés-type metasediments and meta-ophiolites (mostly serpentinites) from the Piemonte-Liguria Ocean. The ophiolitic Schistes lustrés are divided into a lower-plate accretionary prism and an upper-plate system (e.g., Chenaillet; Schmid et al., 2017; Ballèvre et al., 2020; Agard, 2021). The occurrence of a southern prolongation of the Sesia-Dent Blanche unit in the Cottian transect is dubious but shown here to better suggest the correlation with this northern transect. Late Eocene–Oligocene emplacement of Helminthoid flysch nappes over External Briançonnais after Kerckhove (1963) and Kerckhove et al. (1984). Length and thickness of the Briançonnais crust inspired by the natural examples (e.g., Chenin et al., 2017). Approximate position of isotherms 400 °C and 600 °C after Zhao et al. (2020)