Sinistral Brittle-Ductile Shear Zone

Brittle-ductile shear zone marked by an en echelon slightly sigmoidal calcite-filled veins in quartz-bearing limestones, E. Dent de Morcles, Valais, Switzerland. The aproximate boundaries of the shear zone are indicated by the yellow lines. The intersection of the vein tips and the shear zone boundary defines a "V" (red), which points in the opposite direction of the shear sense on the shear-zone boundary. The shear-sense on the shear zone is left-lateral. The older, larger veins are more sigmoidal than the smaller, younger veins. Photo credit: John Ramsay.