Date of this Version
Zebari, M., 2013, Geometry and evolution of fold structures within the High Folded Zone: Zagros Fold-Thrust Belt, Kurdistan Region-Iraq: M.S. Thesis, University of Nebraska-Lincoln.
Understanding the deformation style within the Zagros Fold-Thrust Belt is crucial for understanding the convergence between the colliding Arabian and Eurasian plates and nature of structures that trap hydrocarbons within the belt. The Zagros Fold-Thrust Belt has propagated ~250 km southwest-ward in Northern Iraq. In this study, deformation style of a number of fault-related folds within a part of the belt has been considered. The research intends to understand the geometry and formation mechanisms of these folds, via constructing models for the deformation geometry of folds and associated thrusts at depth using field data and seismic lines and detecting their growth using geomorphic criteria. Aspect ratio of the folds and fold symmetry index were used to categorize fault-related folds. The estimated depth of the detachment level within the sedimentary cover was considered. Folds in the area are broad and box-shaped with close to gentle inter-limb angles and spaced at wavelengths of 5-10 km. The aspect ratio and the fold symmetry index imply that the folds are transitional between fault-bend folds and fault propagation folds. Thick carbonate units in addition to the geometry of related faults govern the broadness and wavelength of the folds. The main detachment level was estimated to be within the Triassic units and the geomorphology of the folds suggests some basement involvement via reactivated basement faults. Thus, cross-sections are constructed with the main structures as fault-bend or fault-propagation folds down to the Triassic level. Geomorphological criteria along folds point to variations along strike and northwest-ward growth of the northwestern side of the Harir, Shakrok/Khatibian, Safin and Bani Bawi/Pirmam Anticlines. Lateral growth of folds is constrained by presence NE-SW oriented strike-slip basement faults. Clear understanding of fold/thrust geometries leads to improved predictions of trapping potential in individual structures in the area. Traps may be segmented via lateral growth of folds and/or influence of basement faults. Comprehending the deformation of sedimentary cover (especially thrust geometry and detachment levels) requires further investigations.
Advisor: Caroline M. Burberry