The geometric and kinematic analyzing of the anticlines and their relation with the large-scale structures are used to determine the structural evolution of the area. The Dorbadam anticline is located in the Kopet-Dagh structural zone, 45 km due north of Quchan and on the Razavi and North Khorasan provinces border. The field study and geometric analysis indicate that the Dorbadam anticline has two culminations with an en-echelon arrangement and different structural evolution. The NW culmination (DA.1) is analyzed as a fault propagation fold geometry, while the SE culmination is known as a simple folding. The axial trend of the Dorbadam anticline has been changed and shows harmonic and Horizontal inclined, 1C subclass of Ramsay's classification, close, asymmetrical over fold in DA.1 part; upright and horizontal, open and symmetrical upright fold in DA.2 part. Aspect ratio on the Dorbadam anticline is 0.64 and has a parabolic appearance. The joint study revealed the existence of five major joints in this area which are bedding and strike joints (tension and compression joints parallel to the axial fold) or dipping joints (tension joints). The systematic joints analyzing of Tirgan Formation with T-Tecto software determined that the trend of maximum stress in the Cretaceous was S07W. The paleo-stress direction determined S25W with axial plane analysis. The Analysis of large-scale faults indicated a change in the stress direction during the time and specified they are post-tectonic and the activity of faults occurred in some various stress systems. تفاصيل المقالة

Lali sub-surface structure, with a NW-SE Zagros trending is located in Dezful Embayment. To determine the folding mechanism, structural geometric parameters including limbs dip, amplitude, wavelength, and crestal length were determined in four stages during deformation. In order to investigate the lateral folding mechanism, these geometric parameters were analyzed in three parts in the Lali structure including northwest, central and southeast. Lali structure in all three sections, show detachment folding mechanism. At the initial stage, due to the rheology of the region's stratigraphic units, the folding mechanism was fault-bend fold and due to the thickness of incompetent units, folding mechanism changes from the fault-bend fold to fault detachment fold and growth of this structure continues with this mechanism. As the deformation continues, detachment folding, the Dahlstrom type inclined to migration type. By identifying the folding mechanism of the Lali structure, determination of the detachment depth was necessary with two computational and graphical methods. Therefore, the depth of this surface was estimated at about 7500-8500 m for Lali structure. This amount is determined at the maximum thickness of the stratigraphic sequence of the region due to the migration of incompetent units to the core of the Lali structure. تفاصيل المقالة