Extended models of transpression and transtension, and application to tectonic settings

Abstract

We introduce a spectrum of transpressional and transtensional deformations that potentially result from oblique plate interaction. Five separate types of deformation are designated, in which a simple shear deformation is combined with an orthogonal coaxial deformation. The types vary in the amount of extension v. contraction, both parallel to the margin and vertically. The interaction between the angle of convergence, kinematic vorticity, infinitesimal strain axes, finite strain, and rotation of material lines and planes is investigated. Quantification of the finite strain indicates that the orientation, magnitude, and geometry (flattening, constriction, etc.) change continually during steady-state transpression.These results are then applied to the cases of transpression, particularly resulting from oblique plate convergence of terranes. The obliquity of plate motion and the geometry of the plate margin determine which of the types of transpression or transtension is favoured. A component of margin-parallel stretching also potentially causes terrane motion to locally exceed oblique plate motion, or move opposite to the general direction of movement between the converging plate boundaries. The kinematic models also suggest that the boundaries between converging terranes are likely to exhibit vertical foliation, but either vertical or horizontal lineation. Finally, narrow transpressional zones between colliding blocks may have very high uplift rates, resulting in exhumation of high-grade metamorphic fabrics.

An Abrupt Transition in the Mechanical Response of the Upper Crust to Transpression along the Queen Charlotte Fault

“…The predicted transition from a pure shear to a simple shear-dominated transpressive regime occurs abruptly at the relatively small angle of 15°rather than at the predicted 20° (Fossen and Tikoff, 1993). Transpression (in the strict definition of Sanderson and Marchini, 1984) lies on a continuum with other types of deformation that could result from oblique convergence (Fossen and Tikoff, 1998). In particular, any along-strike component of elongation will lower the angle of convergence at which the change in behavior occurs.…”

“…Transpression is characteristic of dominantly transform plate boundaries that have a component of convergence (e.g., Sanderson and Marchini, 1984;McCaffrey, 1992;Fossen et al, 1994;Braun and Beaumont, 1995;Walcott, 1997;Fossen and Tikoff, 1998;Chéry et al, 2001). Analytical, numerical, and experimental studies indicate the angle of convergence should have a critical influence on the resulting transpressional deformation.…”

Flexural basin reworked by salt-related pull-apart structures: the Adony Basin

“…The relative importance of strike-slip and thrust faults in a transpressional orogen is determined by the orientation of structures to the regional SHmax, resulting in complex strain partitioning patterns (Jamison 1991;Teyssier et al 1995;Fossen and Tikoff 1998;Cunningham 2007). The evolution from a strike-slip dominated orogen to a thrust dominated one arises from vertical axis rotations (Cunningham 2007).…”

Introduction: the deformation of continental crust and Mike Coward's impact on its understanding

“…The benchmark description of 3D strain patterns by Coward & Potts (1983) provided a framework for many of the general strain studies associated with transpression or transtension (e.g. Fossen & Tikoff 1998). The key to these strain papers in the Moine thrust belt lay in relating the outcrop-scale deformation to the larger-scale geometric evolution of the system, especially to possible displacement gradients that originated from thrust zone propagation.…”