THE TRANSPRESSIONAL STRAIN MODEL APPLIED TO STRIKE-SLIP, OBLIQUE-CONVERGENT AND OBLIQUE-DIVERGENT DEFORMATION

Zones of distributed shear deformation associated with strike-slip and oblique-convergent or oblique-divergent systems accommodate complex three-dimensional strains. Current models suggest that structural orientations within the zones depend on not only the magnitude of shear strain but also the degree of convergence or divergence. The transpressional strain model of Sanderson and Marchini is further developed here, and this study also focuses on relating structural orientations in map view to the magnitude of shear and the degree of convergence or divergence, and to the magnitudes of horizontal and vertical strains. Results include both the mathematical derivation and a set of nomograms relating the model parameters. Applications of the model to field examples and laboratory analogs show how the model can be used to determine the degree of convergence or divergence, and to calculate strain parameters. The model provides geologists with a method to evaluate and predict structural orientations, and to test map and cross-section interpretations.