Issues

COVER: Glacially polished outcrops of granodiorite in the Neves area, South Tyrol, Italy, looking approximately north. The white quartz vein of the north-south fracture set shows an asymmetric sinistral pull-apart step-over. It intersects an east-west aplite dike localizing dextral shear at the boundaries to form an intersection zone nearly perpendicular to the 345° shortening direction. The aplite dike is strongly thinned in this intersection zone. Note the new extensional fracture (joint) marked by iron-staining in the foreground, which is nearly perpendicular to the shortening direction, implying an intermittent switch in principal stress axes during fracturing. See Mancktelow and Pennacchioni, “Intermittent fracturing in the middle continental crust as evidence for transient switching of principal stress axes associated with the subduction zone earthquake cycle” p. 1072–1076.