Transpressional and transtensional deformation zones can be modeled as a simple shearing with a simultaneous component of pure shearing in the plane perpendicular to the zone. Four general types of deformation (pure shear- and wrench-dominated transpression/transtension) are distinguished on the basis of the instantaneous stretching axes. For each of these deformations the orientation of the finite strain ellipsoid, instantaneous stretching directions, flow apophyses, and rotation paths of lines and planes can be calculated. These quantities are reftected in the fabrics of deformed rocks ( orientation and intensity of lineations, foliations, etc.) which can be used to qualitatively or quantitatively describe the deformation of both active and ancient transpressional/transtensional deformation zones. Partitioning of transpressional/ transtensional displacement fields into pure shear-enhanced transpressional/transtensional domains separated by narrower strike-slip shear zones or faults can be modeled in the kinematic framework presented here, and may be applied to centimeter scale partitioning as well as to partitioning at the scale of plate boundary deformation zones.
H. Fossen, Statoil, GF/PETEK-GEO, N-5020 Bergen, Norway;
B. Tikoff & C. Teyssier, Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA