Geometry, kinematics, and mechanics of decollement folding

Despite much previous research, important issues regarding the geometry, kinematics, and mechanics of decollement folding remain unaddressed. This dissertation presents the results of investigations into problems regarding the geometric, kinematic, and mechanical evolution of decollement folds using empirical, analog modelling and theoretical approaches.; Displacement-distance analysis of fault propagation, fault bend, and decollement fold models reveals that displacement gradients on fault surfaces are not necessarily related to fault tip propagation. This suggests that measured relative stretch values can not be reliably used to determine the propagation histories of natural faults.; The geometries of decollement folds in the Boule and Fiddle Ranges of the Canadian Rocky Mountains originate on multiple decollement zones and exhibit a wide range of highly complex geometries. Because of this geometric complexity, folds in the Boule and Fiddle Ranges can not be approximated by existing decollement fold models.; Analysis of variations in chemical compositions around a similar fold in the Boule Range constrains the compositional evolution during fold-related deformation. Although textural evidence, such as cleavage and fibrous overgrowths, suggests local mass redistribution on the scale of millimeters, compositional trends support negligible volume flux at the scale of the fold.; Centrifuge modelling experiments designed to evaluate the influence of decollement properties on fold geometry reveal that, contrary to previous studies, decollement properties are as important as the material properties of the most competent structural lithic units in determining fold geometries. The observed wavelengths of decollement folds in the Boule and Fiddle ranges are largely consistent with these experimental results.; In the general shear similar fold model, deformation in the hinge zone is characterized by pure shear, and deformation on fold limbs is characterized by components of both simple and pure shear (general shear). Predicted strain distributions and fabric orientations for this model differ from those of existing models (oblique simple shear, chevron, and kink models), and are more consistent with observations from natural folds.