both S-C and S-C' structures matches that of the shear zone in which they are found. Other microstructures which can give sense of shear include: sigmoidal veins mica fish rotated porphyroclasts asymmetric boudins (Figure 1) asymmetric folds Transpression Transpression regimes are formed during oblique collision of tectonic plates and during non-orthogonal subduction. Typically a mixture of oblique-slip thrust faults and strike-slip or transform faults are formed. Microstructural evidence of transpressional regimes can be rodding lineations, mylonites, augen-structured gneisses, mica fish and so on. A typical example of a transpression regime is the Alpine Fault zone of New Zealand, where the oblique subduction of the Pacific Plate under the Indo-Australian Plate is converted to oblique strike-slip movement. Here, the orogenic belt attains a trapezoidal shape dominated by oblique splay faults, steeply-dipping recumbent nappes and fault-bend folds. The Alpine Schist of New Zealand is characterised by heavily crenulated and sheared phyllite. It is being pushed up at the rate of 8 to 10 mm per year, and the area is prone to large earthquakes with a south block up and west oblique sense of movement. Transtension Transtension regimes are oblique tensional environments. Oblique, normal geologic fault and detachment faults in rift zones are the typical structural manifestations of transtension conditions. Microstructural evidence of transtension includes rodding or stretching lineations, stretched porphyroblasts, mylonites, etc. See also Convergent boundary Crenulation Fault (geology) Foliation (geology) Rock microstructure Strain partitioning Sense of shear indicators: dextral and sinistral References Diagrams and definitions of shear (Wayback Machine), by University of the West of England, Bristol. Archive copy incomplete, 12/31/2012. Structural geology Geological processes Deformation (mechanics)