Folding style of the Jarik Anticline, NE Dezful Embayment of Zagros Belt, the role of thickness changing of the folded layers and syntectonic deposition

Abstract

Detecting the style changes and folding mechanism of anticlines in the Dezful Embayment, an oil-rich area, in the SW Zagros Fold-Thrust Belt have important applications for hydrocarbon exploration. The present study, according to the field, seismic and well data, investigates the effects of multiple factors such as detachment horizon, halokinetic process, syn-tectonic sedimentation and thickness variation on the folding style through the Jarik Anticlines in the northeast of Dezful embayment. Due to the above-mentioned factors, the Jarik Anticline shows a variable folding geometry both along the anticline strike and from the surface to the depth. The Jarik Anticline, as a detachment fold, was formed in the Fars passive Group and decoupled from the deep structures by Gachsaran evaporites (as strong detachment horizon). In the northwestern termination where the Passive Group has a considerable thickness (up to 2500 m); the Jarik Anticline displays the Lift-off detachment geometry. In contrast, from the middle segment to SE termination of the anticline thickness reduction of the Passive Group led to the formation of the asymmetric faulted detachment fold. These thickness changes of the Passive Group are the result of the interaction between deposition of this group (as syn-tectonic deposits), both laterally and vertically movements of the Gachsaran evaporites and folding of the Competent Group under the detachment horizon. Based on the results of this research, the possible development of the large subsurface anticlines under the uplifted surface growth synclines must be considered in the future exploration studies.