Emplacement of foreland thrust systems

Abstract

Emplacement‐driving mechanisms for thrust systems have been briefly reviewed and compared with distinctive structural styles in thrust belts. A B‐type mode, which implies a push from the rear and an elastic‐brittle behavior of the rock mass, appears to be suitable as a general model for the emplacement of thrust sheets in thin‐skinned fold and thrust belts where stratal shortening of sedimentary covers and imbrication of upper level crustal rocks occur. In such an environment that the mechanical behavior of the crustal section involved the mode, and timing of deformation, and the geometry of thrust systems are all strongly dependent upon the coupling between induced tectonic strain and transient, close to lithostatic pore fluid pressure buildup over a critical areal extent. The model presented here does not require a weak basal horizon for the detachment of thrust sheets, and pore pressure Pp does not need to be high at once under the entire length of the thrust wedge. Rather, the transient buildup of Pp and hence the spatial and temporal progressive weakening of the rock mass are directly coupled with deformation.