Clues to inferred different thrust-related fold models and thin-thick skinned tectonics within a single folded structure in Iraqi Zagros, Kurdistan region

摘要

The Maqloub-BardaRash structure is situated at the Low Folded Zone within the NW of the Zagros fold-thrust belt in the Iraqi Kurdistan region. One of the main goals of this work is to reveal the variation in the fold architecture and fault shape with depth to build a plausible fold model, as well as to explain the kinematic evolution of the Maqloub-BardaRash structure. The middle part of the anticlinal hinge line of the studied structure shows deviation and anticlockwise rotation. This character is ascribed to the presence of a north-south trending left-lateral strike-slip fault. This fault is considered to be a deep-seated basement fault that likely caused segmentation of Maqloub-BardaRash structure into two parts: the northwestern Maqloub structure which exhibits a normal asymmetry and the southeastern BardaRash structure with a reverse asymmetry. The balanced cross sections based on the top of Middle Miocene Fatha Formation from the studied structures displays a maximum total horizontal shortening of 14% for the Maqloub structure and 9.89% for the BardaRash segment at the same stratigraphic level. Through the Maqloub section, the thrust-related shortening increases downsection, whereas the fold-related shortening increases upsection. Whereas along BardaRash section, the fold-related shortening smaller irregular variations at different stratigraphic levels are evidenced. The Maqloub segment is interpreted as a fault-propagation fold, but the BardaRash segment is interpreted as a faulted detachment fold based on the geometrical analysis of deformed models. Based on the resulting deformed geometries from the balanced cross sections, the propagation of the Maqloub segment is associated with the activation of an underlying basement fault, whereas the BardaRash segment is decoupled along the Triassic ductile sequence. The structural characterization of two different models of the fault-related deformation along the individual Maqloub-BardaRash folded structure will enh