A study of fold characteristics and deformation style using the evolution of the land surface: Zagros Simply Folded Belt, Iran

Abstract

AbstractDeformation styles within a fold–thrust belt can be understood in terms of the spatial organization and geometry of the fold structures. In young fold–thrust belts such as the Zagros, this geometry is reflected topographically by concordant landform morphology. Thus, the distribution of deformation structures can be characterized using satellite image analysis, digital elevation models, the drainage network and geomorphological indicators. The two distinct fold types considered in this study (fault-bend folds and detachment folds) both trending NW–SE, interact with streams flowing NE–SW from the High Zagros Mountains into the Persian Gulf. Multiple abandoned stream channels cross fault-bend folds related to deep-seated thrust faults. In contrast, detachment folds, which propagate laterally relatively rapidly, are characterized by diverted major stream channels and dendritic minor channels at the fold tips. Thus these two fold types can be differentiated on the basis of their geometry (fault-bend folds, being long, linear and asymmetrical, can be distinguished from detachment folds, which tend to be shorter and symmetrical) and on their associated geomorphological structures. The spatial organization of these structures in the Zagros Simply Folded Belt indicates that deformation is the result of the interaction of footwall collapse and the associated formation of long, linear fault-bend folds, and serial folding characterized by relatively short periclinal folds. Footwall collapse occurs first, followed by serial folding to the NE (i.e. in the hanging wall of the fault-bend folds), often on higher detachments within the sediment pile.