Styles of continental contraction: A review and introduction
Published:January 01, 2006
Continental lithosphere within sites of relative plate convergence can display a wide range of different styles of contractional deformation. Traditionally, crustal-scale deformation can be described in terms of end-member behaviors—thin-skinned (dominated by substantial detachment horizons) and thick-skinned (dominated by crustal-scale ramps). Consequently, these descriptions have implied different degrees of basement involvement in thrust belts. Additionally, tracts of ductile deformation can be described as approximating to one of two end-member, plane strain models: simple shear and pure shear. While strongly localized high-strain zones require large simple shear components, this need not be the case for broad tracts of continuous ductile deformation.
Studies of ancient systems have emphasized the role of simple shear. In contrast, insights from active orogens from geodetic and seismological studies suggest that substantial volumes of the continental lithosphere deform in a continuous fashion that does not approximate to simple shear. Broadly distributed strain involving volumes of weak crust might be promoted by enhanced temperatures and/or the widespread development of weak, hydrated minerals. These rheological controls are likely to evolve during the development of complex orogenic systems and lead to changes in the deformation styles through the continental lithosphere in space and time.