Lateral Heterogeneity in Compressional Mountain Belt Settings

Abstract

Analysis of convergent orogens reveals important orthogonal/cross structures and laterally heterogenous deformation style, igneous activity, metamorphic grade geomorphology and seismic activity. To assess the occurrence, causal mechanisms, and implications of these lateral heterogeneities, we review a selection of convergent orogens with different tectonic settings and history. We find that heterogeneities are primarily driven by the preexisting deformational history of the cratonic blocks involved, lateral change in lithology of crustal rocks, variations in rheologic properties, or changes in plate kinematics. The Appalachian orogenic front mimics the Iapetan rift margin. As seen in the Zagros and the Cordillera, preexisting basement structures have control on preorogen and synorogenic sedimentation, which subsequently impact how the orogenic wedge evolves. Several cross faults in the Himalaya spatially coincide with basement structures on the downgoing plate. Similarly, physiography of the subducting oceanic plate influences deformation in the overriding plate of Andean-type margins. Orogenic extension in the Alps has been accompanied by a system of orogen-parallel strike slip faults and extensional cross faults. It is evident that lateral heterogeneities can form crucial control on the evolution of orogenic belts and can influence seismic rupture patterns, resource occurrence, and landslide hazards.