Patterns of imbricate thrusting

Through the use of seismic reflection profiles, satellite images, and balanced kinematic models, we describe patterns that help to identify imbricate structures and define the sequence of thrusting in fold-and-thrust belts. Measures of folding shear strains are employed to define break-forward systems in which younger, deeper faults refold overlying thrust sheets. In contrast, break-backward sequences form a wide range of viable geometries that are not expected to conserve these folding strains. Thus, measures of folding shear strains provide a means to define thrusting sequence. We also explore map-view patterns of imbricate thrusting by using three-dimensional models and stereoscopic satellite images. We present an example from the Peruvian Andes in which these map patterns are combined with seismic reflection profiles to define a complex imbricate system with components of both break-forward and break-backward thrusting. These integrated methods provide new tools for understanding the deformational histories of fold-and-thrust belts, including the definition of complex structural closures with opportunities for hydrocarbon-reservoir duplication.