Fig. 13

Synthetic sketches of the SFZ evolution relative to the Southern Steep Belt. a, b Schematic structural map of the SFZ between 18.5–14.5 and 14.5–3 Ma. c, d Scenario A: NW–SE cross-section of an initially shallow SFZ crosscutting the Southern Steep Belt (18.5–14.5 Ma), with late shortening and steepening of the SFZ and a transecting relationship with regard to the Southern Steep Belt (14.5–3.0 Ma). e, f Scenario B: NW–SE cross-section of the SFZ with an initially steep geometry in the south (18.5–14.5 Ma), and late shortening and steepening of the SFZ but with a parallel relationship to the Southern Steep Belt (14.5–3.0 Ma). SSB Southern Steep Belt, PF Periadriatic Fault, CF Centovalli Fault, SL Simplon Line, Sm2 younger ductile-to-brittle mylonitic foliation related to the SFZ, Sm older ductile mylonitic foliation related to the SFZ, S _1/2 pre-existent regional fabric associated to the D1–D2 deformation phase, B Berisal backfold, G Glishorn backfold, V Vanzone backfold, M Masera backfold. Active faults are in bold and the axial planes indicate the active folds