GEOMETRY AND EVOLUTION OF FOLD STRUCTURES WITHIN THE HIGH FOLDED ZONE: ZAGROS FOLD-THRUST BELT, KURDISTAN REGION-IRAQ

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. Burberr

Late Pleistocene‐Holocene Slip Rates in the Northwestern Zagros Mountains (Kurdistan Region of Iraq) Derived From Luminescence Dating of River Terraces and Structural Modeling

Abstract A significant amount of the ongoing shortening between the Eurasian and Arabian plates is accommodated within the Zagros Fold‐Thrust Belt. However, the spatial and temporal distribution of active shortening within the belt, especially in its NW part, is not yet well constrained. We determined depositional ages of uplifted river terraces crossing the belt along the Greater Zab River using luminescence dating. Kinematic modeling of the fault‐related fold belt was then used to calculate long‐term slip rates during the Late Pleistocene to Holocene. Our results provide new insight into the rates of active faulting and folding in the area. The Zagros Mountain Front Fault accommodates about 1.46 ± 0.60 mm a −1 of slip, while a more external basement fault further to the SW accommodates less than 0.41 ± 0.16 mm a −1 . Horizontal slip rates related to detachment folding of two anticlines within the Zagros Foothills are 0.40 ± 0.10 and 1.24 ± 0.36 mm a −1 . Basement thrusting and thickening of the crust are restricted to the NE part of the Zagros belt. This is also reflected in the regional topography and in the distribution of uplifted terraces. In the southwestern part, the deformation is limited mainly to folding and thrusting of the sedimentary cover above a Triassic basal detachment. In the NE, deformation is associated with slip on basement thrusts. Our study sheds light on the distribution of shortening in the Zagros Mountains and helps to understand the regional tectonic system. Our results may be the foundation for a better seismic hazard assessment of the entire area.Plain Language Summary In active mountain belts, river terraces found above the present‐day river level can be indicative of differences in uplift rates due to the thickening, faulting, and folding processes in the Earth's crust. These processes, driven by the motion of tectonic plates, are responsible for the formation of mountain belts. Here, we took sediment samples from uplifted river terraces along the Greater Zab River that crosses the Zagros Mountains in the Kurdistan Region of Iraq. We determined their deposition age using luminescence dating. From their age and elevation, we calculated uplift rates. We built a geometrical model of the fault zones in the area and determined how fast the slip occurs on these faults based on the uplift rates. Our results indicate that there were less than two millimeter per year of slip on these faults on average during the last 60 thousand years. This motion is a result of the convergence between the Arabian and Eurasian plates. With studies like this we can measure how fast fault blocks move, even if they were not associated with large earthquakes in the recent past. This approach helps to better assess the potential earthquake hazard in the area under investigation.Key Points We estimated fault slip rates in the NW Zagros Mountains by luminescence dating of river terraces and structural modeling There is c. 1.46 mm a −1 slip on the Mountain Front Fault and c. 1.64 mm a −1 slip from detachment folding in the NE part of the Foothill Zone Crustal thickening and basement thrusting occur in the NE parts of the Foothill Zone and only cover deformation occur in the SW part

Geomorphology of the northwestern Kurdistan Region of Iraq: landscapes of the Zagros Mountains drained by the Tigris and Great Zab Rivers

We present the geomorphological map of the northwestern part of the Kurdistan Region of Iraq, where the landscape expresses the tectonic activity associated with the Arabia-Eurasia convergence and Neogene climate change. These processes influenced the evolution of landforms and fluvial pathways, where major rivers Tigris, Khabur, and Great Zab incise the landscape of Northeastern Mesopotamia Anticlinal ridges and syncline trough compose the Zagros orogen. The development of water and wind gaps, slope, and karsts processes in the highlands and the tilting of fluvial terraces in the flat areas are the main evidence of the relationship between tectonics, climate variations and geomorphological processes. During the Quaternary, especially after the Last Glacial Maximum, fluctuating arid and wet periods also influenced local landforms and fluvial patterns of the area. Finally, the intensified Holocene human occupation and agricultural activities during the passage to more complex societies over time impacted the evolution of the landscape in this part of Mesopotamia

Structural style and long-term slip rates in the Zagros Fold-Thrust Belt (Kurdistan Region of Iraq) derived from structural modeling, luminescence dating of river terraces and tectonic geomorphology

The Zagros Mountain Front Flexure is one of these major boundaries and forms a prominent topographic and structural step in the frontal part of the Zagros Belt. This study focuses on the Mountain Front Flexure in Kurdistan Region of Iraq. the structural style at depth is constrained from the balanced cross-section and structural forward modeling. The long-term fault slip rates are calculated for several structure from the uplifted river terraces on the banks of the Greater Zab River. The landscape maturity of several frontal anticlines was assessed to estimate difference in their relative uplift time using geomorphic indices and landscape evolution modeling. The results show that the structural evolution is represented by a multi-stage deformation. The thin-skinned deformation above the Triassic detachment was evolved first. Then, a basement thrust was evolved in the deformation and the basement thrusting is responsible for the structural step across the Mountain Front Flexure. The faults in the area are active. The basement fault below the Zagros Mountain Front Fault accommodates about 1.46±0.60 mm a-1 of slip, while a more external basement fault further to the SW accommodates less than 0.41±0.16 mm a-1. Horizontal slip rates related to detachment folding of Safin and Sarta anticlines within the Zagros Foothills are 0.40±0.10 and 1.24±0.36 mm a-1, respectively. There is difference in the landscape maturity of the frontal anticlines, and their relative uplift time. The resulting interpretation from the landscape maturity is that Akre Anticline was the first to uplift among the studied anticlines, followed by Perat Anticline and Harir Anticline. It can be inferred that uplift of the Akre and Perat anticlines started 160200 and 80100 kyr, respectively, before that of the Harir Anticline

4-D evolution of anticlines and implications for hydrocarbon exploration within the Zagros Fold-Thrust Belt, Kurdistan Region, Iraq

The Zagros Fold-Thrust Belt, extending from southern Iran, through northern Iraq and into Turkey, is characterized by elongate NW-trending anticlines that house large hydrocarbon accumulations. In recent years, the Kurdistan region of northern Iraq has become an area of interest for both structural studies and petroleum exploration-related investigation. Key questions to be answered concern the nature of the anticlines and whether the geometry of any associated thrusts can be predicted from surface geomorphology, as well the 4-D evolution of the area and along-strike continuity of the anticlines. To address these questions, this study combines field data, remote-sensing data concerning the structure and geomorphology of the anticlines, and structural modeling in order to produce robust interpretations of the geometries of the reverse fault structures that core the majority of these anticlines. Results indicate that this methodology can be used to constrain potential thrust configurations at depth and the probable style of fold amplification and lateral propagation. In addition, this study shows that the growth of the anticlines can be considered in 4-D, with consideration given to the interaction of the Zagros-age deformation with the pre-existing basement fabric. We demonstrate that combining both structural and geomorphological methodologies can lead to a better understanding of the geometry and evolution of the trap-forming structures in the Kurdistan region of Iraq and thus is expected to be of interest to the petroleum industry

Geomorphology of the Central Kurdistan Region of Iraq: landscapes of the Erbil Plain between the Great Zab and Little Zab Rivers

ABSTRACTWe present the result of the geomorphological mapping of the central sector of the Kurdistan Region of Iraq. Therein, landscape evolution was mostly overseen by the regional geodynamic, related to the Arabia-Eurasia convergence, and in the Quaternary, regional climate fluctuations contributed to shaping landforms. The combination of such processes affected the distribution, types, and evolution of landforms (related to structural, hillslope, fluvial, and karst processes), with a noteworthy influence on the development of the local drainage network, which belongs to Tigris River catchment. The Great Zab and Little Zab Rivers – the main left tributaries of Tigris River – progressively cut anticline ridges growing in the area. Our analyses suggest that the structural deformation of the Zagros also controlled the evolution of the low-order channels of the hydrographic network. Since the Holocene, landforms dynamic was altered by intense human exploitation of the landscape and increased fluctuations between arid and humid conditions

Late Pleistocene‐Holocene Slip Rates in the Northwestern Zagros Mountains (Kurdistan Region of Iraq) Derived From Luminescence Dating of River Terraces and Structural Modeling

A significant amount of the ongoing shortening between the Eurasian and Arabian plates is accommodated within the Zagros Fold‐Thrust Belt. However, the spatial and temporal distribution of active shortening within the belt, especially in its NW part, is not yet well constrained. We determined depositional ages of uplifted river terraces crossing the belt along the Greater Zab River using luminescence dating. Kinematic modeling of the fault‐related fold belt was then used to calculate long‐term slip rates during the Late Pleistocene to Holocene. Our results provide new insight into the rates of active faulting and folding in the area. The Zagros Mountain Front Fault accommodates about 1.46 ± 0.60 mm a−1 of slip, while a more external basement fault further to the SW accommodates less than 0.41 ± 0.16 mm a−1. Horizontal slip rates related to detachment folding of two anticlines within the Zagros Foothills are 0.40 ± 0.10 and 1.24 ± 0.36 mm a−1. Basement thrusting and thickening of the crust are restricted to the NE part of the Zagros belt. This is also reflected in the regional topography and in the distribution of uplifted terraces. In the southwestern part, the deformation is limited mainly to folding and thrusting of the sedimentary cover above a Triassic basal detachment. In the NE, deformation is associated with slip on basement thrusts. Our study sheds light on the distribution of shortening in the Zagros Mountains and helps to understand the regional tectonic system. Our results may be the foundation for a better seismic hazard assessment of the entire area.Plain Language Summary: In active mountain belts, river terraces found above the present‐day river level can be indicative of differences in uplift rates due to the thickening, faulting, and folding processes in the Earth's crust. These processes, driven by the motion of tectonic plates, are responsible for the formation of mountain belts. Here, we took sediment samples from uplifted river terraces along the Greater Zab River that crosses the Zagros Mountains in the Kurdistan Region of Iraq. We determined their deposition age using luminescence dating. From their age and elevation, we calculated uplift rates. We built a geometrical model of the fault zones in the area and determined how fast the slip occurs on these faults based on the uplift rates. Our results indicate that there were less than two millimeter per year of slip on these faults on average during the last 60 thousand years. This motion is a result of the convergence between the Arabian and Eurasian plates. With studies like this we can measure how fast fault blocks move, even if they were not associated with large earthquakes in the recent past. This approach helps to better assess the potential earthquake hazard in the area under investigation.Key Points: We estimated fault slip rates in the NW Zagros Mountains by luminescence dating of river terraces and structural modeling. There is c. 1.46 mm a−1 slip on the Mountain Front Fault and c. 1.64 mm a−1 slip from detachment folding in the NE part of the Foothill Zone. Crustal thickening and basement thrusting occur in the NE parts of the Foothill Zone and only cover deformation occur in the SW parts.German Academic Exchange Service (DAAD) http://dx.doi.org/10.13039/501100001655German Research Foundation (DFG) http://dx.doi.org/10.13039/50110000165

Luminescence Dating of River Terraces along the banks of the Greater Zab River in the Northwestern Zagros Mountains in Kurdistan Region of Iraq

This dataset contains details of 15 samples of the river terraces that were collected along the banks of the Greater Zab River (Kurdistan Region of Iraq) that crosses the Zagros Fold-Thrust Belt. These terraces were dated using luminescence dating including both Infrared Stimulated Luminescence (IRSL) and post-IR IRSL (pIR) to determine their depositional ages. The dataset includes details about the locations, dosimetry, and determined ages of the collected samples. The ages of the dated river terraces range from c. 165 ka to c. 6 ka. The terraces were deposited at the river level. Their present-day elevation above the river is interpreted as the amount of incision by the river that occurred in response to the uplift. The uplift rates of river terraces were integrated with kinematic modeling of the fault-related fold belt in the area to calculate long-term slip rates during the Late Pleistocene to Holocene. Our results provide new insight into the rates of active faulting and folding in the area. The Zagros Mountain Front Fault accommodates about 1.46±0.60 mm a-1 of slip, while a more external basement fault further to the SW accommodates less than 0.41±0.16 mm a-1. Horizontal slip rates related to detachment folding of two anticlines within the Zagros Foothills are 0.40±0.10 and 1.24±0.36 mm a-1, respectively

The role of salt supply, dissolution, and erosion on the surface deformation of emergent salt diapirs based on analysis of Persistent Scatterer Interferometry data

In the emergent (subaerial) salt diapirs, the salt faces negative buoyancy when extruded to the surface, and flows outward around their vent by gravity spreading. It also faces dissolution and erosion. Salt supply, salt flow, dissolution, and erosion also influence the diapir’s shape. Although satellite geodesy monitors the surface deformation of the salt-caprock glacier system, the interpretation of the resulting deformation pattern in terms of salt supply, dissolution, and erosion is not straightforward. To overcome these shortcomings, we analyze surface deformation pattern of a fountain-shaped and nearly symmetrical diapir (Finu) within the Zagros Belt of Iran using Persistent Scatterer Interferometry (PSI). The PSI data are extracted from the Sentinel-1 SAR images using the Integrated Wide Area Processor (IWAP) at the German Aerospace Center (DLR) covering four years from October 2014 to December 2018. The line-of-sight signal from the PSI data is decomposed into the vertical and horizontal deformation signals. Within the diapir, the deformation signal is then spatially correlated with the influencing factors, including local position within the diapir, slope, karstification, and drainage. Along an E-W profile across the diapir, two-dimensional deformation vectors reflect salt supply and spreading; therefore, the magnitude and direction of these vectors are influenced by their local position within the diapir and the slope. There is a slight uplift in the central part of the salt domes with active salt extrusion. The deformation vectors divert outward in the slope direction, and the deformation reaches its maximum magnitude at the upper flanks of the central dome. The deformation decreases in the outer flat plateau regions of the extrusions and continues to decrease in the steep slopes at their lateral terminations. Along the same profile, relatively higher subsidence is detected in areas where sinkholes are abundant. In these regions, salt is removed in the subsurface by dissolution-driven karst development in contrast to areas where the surface drainage system is developed, and fluvial erosion is dominant. In the future, a better understanding of the factors controlling salt spreading around the vent and the impacts of dissolution/erosion mechanisms on the deformation will improve our ability to interpret surface deformation of the salt-caprock system at unprecedented spatial and temporal resolution