Document Type : Original Research Paper
Author
Assistant Professor, Department of Geology, Faculety of Earth Sciences, Shahid Beheshti University, Tehran, Iran
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 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.
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