Deformation analysis and folding style in the Marun and Kupal anticlines based on seismic reflection data, Dezful Embayment

Despite hydrocarbon importance of the Dezful Embayment, there is no systematic study on generation of its structures. This study aims the folding style and stages of progressive deformation, revealed based on 5 interpreted horizons, from top Kangan to top Gachsaran Member-6, on 15 seismic profiles in the Marun and Kupal anticlines. Results show that at first stage of folding harmonic and similar fold has been formed, then with the increasing deformation the faults have been generated. In addition, wavelength and shape of folds in younger Formations, Mishan and Aghajari, are different from those of older pre-Gachsaran Formations. This evidence confirms that Gachsaran has been acted as a major detachment from the early stages of folding. Long gently dipping backlimb and short gently dipping forelimb exhibit that a regional slope of layers has been existed before inception of folding. During the progressive deformation, primary gentle symmetric folds with rounded hinge areas have been changed into open asymmetric folds with angular hinge zones. With deformation increasing, Triassic Dashtak evaporative unit is activated first as a middle detachment level. Then, in further stages of deformation, Lower Cretaceous shale, Garu Formation, has been activated. Based on the available data, folding style in the Marun and Kupal anticlines is of faulted detachment folding type, with limb rotation fold growth kinematic mechanism that changed into a combination of limb rotation and hinge migration with increased deformation. The Kupal anticline exhibits more simple deformation in comparison with the Marun anticline. Thus, it seems that the Kupal shows us previous stages of deformation in the Marun anticline.