Influence of the Gachsaran Formation lithostratigraphy on its decoupling behaivior on Zagros Frontal Fault hanging wall anticlines in the southern Dezful Embayment

The mechanical properties of incompetent rocks play a crucial role in controlling the deformation style of fold-thrust belts. Disharmonic folding occurs due to the act of detachment layers, in which surficial fold shapes doesn’t reflect their deeper geometry. The Gachsaran Formation is the most significant detachment layers across the Zagros folded belt zone. In this study, field data, interpretation of subsurface data (2D seismic lines, UGC maps and well data) together with surface geological mapping, permit to measure crestal shift of anticlines, Aghajari, Pazanan, Rage-sefid, BibiHakimeh, Sulabdar and Nargesi in the southern Dezful Embayment. The results show the effect of the Gachsaran Formation on the folding style. Since the Gachsaran Formation has different lithology in the southern Dezful Embayment, the results of this study indicated that salt content and thickness variations of the Gachsaran Formation controls its behavior as a decoupling level and their effect on disharmonic, change in folding styles and in shifting of folds’ hinge zone.