E Tavakolian; A Yassaghi
Abstract
The Zagros fold-thrust belt has been cut out by various transverse faults with segments displaying en-echelon pattern. Depending on the type of overlapping and fault mechanisms, restraining and releasing zones have been developed between these en-echelon segments. The NW-trending dextral Sabzpushan fault ...
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The Zagros fold-thrust belt has been cut out by various transverse faults with segments displaying en-echelon pattern. Depending on the type of overlapping and fault mechanisms, restraining and releasing zones have been developed between these en-echelon segments. The NW-trending dextral Sabzpushan fault is one of these transverse strike-slip faults located in the Fars province of the Zagros belt. Since the Sabzpushan fault zone consists of several en-echelon segments of clockwise pattern, restraining zones have been generated between them. One of these restraining zones is developed on the NW nose of the Chaghal anticline. Detailed field studies and interpretation of satellite images resulted in identification of several dextral en-echelon faults in the western part of the Chaghal anticline. This fault zone consists of two en-echelon faults called Qir and Harm. Different kinds of structures such as dextral faults with reverse component, thrust faults, minor duplexes and young minor folds were mapped in these restraining zones. These structural assemblages are similar to those that are developed in the restraining zones produced in physical models of en-echelon strike-slip faults. In addition, similar restraining zones which are also observed across the Ghol Ghol and Sefidar anticlines to the south and north of the Chaghal anticline, respectively, are attributed to other en-echelon segments of clockwise array along the Sabzpushan fault zone. These dextral en-echelon faults along the Sabzpushan fault, which are interpreted as surface ruptures in the sedimentary cover with basal detachment zone, formed as a result of the activity of Sabzpushan fault in the basement.
H Hajialibeigi
Abstract
The E-W trending deep-seated Balarud fault zone is formed the part of Mountain Front Fault in north of Andimeshk. This strucutre has been separated the Lurestan zone (in North) from the Dezful Embayment (in South) that has operated as a faulted zone. Several subsurfaial and surface anticlines are affected ...
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The E-W trending deep-seated Balarud fault zone is formed the part of Mountain Front Fault in north of Andimeshk. This strucutre has been separated the Lurestan zone (in North) from the Dezful Embayment (in South) that has operated as a faulted zone. Several subsurfaial and surface anticlines are affected by this fault zone. In this paper for some of these anticlines have been drawn the cross-sections that based on well data, interpreted seismic profiles and field observations. The geometrical characteristics of these anticlines analyzed from cross-sections. The achievement of these analyses is used for distinguishing the tectonics and the deformational pattern in the Balarud fault zone. These anticlines formed by following mechanism: detachment folding, fault-propagation folding and fault-bend folding. The change of the deformational style and type of these anticlines are related to present and absence of the intermedate detachment horizons and also contorted by influence of this fault zone. These anticlines that have less 100 km lengths are En echelon arrayeh, asymmetric, disharmonic, noncylindrical, convolute folds with SW vergence and helicoidally axial surfaces. The Lurestan zone is more folded than the Dezful Embayment zone. The Balarud fault zone is a sinistral simple shear zone due to influence of strike-slip fault with E-W trending in basement. It seams the strike-slip movement sinisteral component of deap-seated fault is provided a helicoidally geometry in the study area. Different mechanism of fault-related folds of these anticlines and the results of the demonstration of the style of layer folded confirm the helicoidally geometry. Direction of fault is generally due to North and gradually become vertical to subvertical in adjacent to basement. The Balarud fault zone is an oblique footwall-ramp system with oblique convergence and the Kazerun fault zone is also another member of this system. The sinistral and dextral movements respectively, have been caused by a part of the promontory of Arabian plate between these fault zones. A transition zone is formed that the structural geology process and tectonics mechanism in duration of this ramp are different. The Balarud fault zone is not continuous, and has been displaced by many strike-slip basement involved faults. A NW-SE basement fault (α fault) as a tear fault cuts the sheet of the Balarud fault parallel to the Kabir Kuh anticline.
S Rezaei; A Yassaghi
Abstract
The aspect ratio of folds is among the most important parameters indicating geometrical features of folds. Based on the aspect ratio, folds are categorized into two groups of buckle and forced folds. The NW-SE trending Qitoleh anticline, which is located in NW of the Lurestan structural subzone and in ...
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The aspect ratio of folds is among the most important parameters indicating geometrical features of folds. Based on the aspect ratio, folds are categorized into two groups of buckle and forced folds. The NW-SE trending Qitoleh anticline, which is located in NW of the Lurestan structural subzone and in the vicinity of the High Zagros Fault, has unique structural characteristics that make it different from other folds in the Zagros Folded Belt. In rock units older than Cretaceous, the anticline consists of four en-echelon buckle folds whereas shows high aspect ratio and forced fold geometry in Tertiary units. Such a variation in the fold style from the surface down to the depth is interpreted as the imposed influence of the High Zagros Fault on intermediate detachment horizons. Such a fold style, which is also observed in other anticlines neighboring the SE part of High Zagros Fault, can be used as a model to interpret similar folds adjacent to the major reverse basement faults in other parts of the Zagros belt.
