Fig. 10

Structural observations and data from the Vals region between Leis and Zervreila Lake. a Gneiss with quartz veins (R: 731,992, H: 163,408). View of the X–Z plane of the Leis-Phase deformation (foliation 070/21, stretching lineation 055/16). Polycrystalline quartz aggregates have sigmoidal shape indicating dextral (top-to-the-NE) shear sense. b Stereoplot of Zapport foliation poles (black dots) on a great circle indicating fold axis orientation of the Leis phase (fold axis 055/15). This is similar to the orientation in Val Scaradra region (Fig. 4). Measured stretching lineations (green dots) also dip shallowly to the NE and belong to the Leis phase. c Orthogneiss at the front of the Adula Nappe at Fuorcla da Puozas, north of Lake Zervreila. The foliation, forming the outcrop surface, is oriented 345/52 and the obvious, strong stretching lineation 067/10. Both represent the Leis Phase. View towards south. d Thin section of quartz vein taken to the north of Zervreila Lake (F 033/18, L 053/11). Thin section (with crossed polarizers and gypsum plate inserted, width of thin section 6.9 mm) parallel to X–Z plane of the Leis Phase shows addition colours (blue), indicating quartz-c-axes rotated clockwise from the Z-direction (shear sense top-to-the-NE)