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


1 Department of Geology, Tarbiat Modares University, Tehran, Iran

2 Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, Iran

3 National Iranian South Oil Company (NISOC)


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.


Bahroudi, A., Koyi, H.A., 2003. Effect of spatial distribution of Hormuz salt in deformation style in the Zagros fold-and-thrust belt: An analog modeling approach. Journal of the Geological Society 160, 719–733. DOI:10.1144/0016-764902-135.
Casciello, E., Vergés, J., Saura, E., Casini, G., Fernandez, N., Blanc, E. J.P., Homke, S., Hunt, D., 2009. Fold patterns and multilayer rheology of the Lurestan Province, Zagros Simply Folded Belt (Iran). Journal of the Geological Society 166, 947–59. DOI:10.1144/0016-76492008-138.
Cotton, J.T., Koyi, H.A., 2000. Modeling of thrust fronts above ductile and frictional detachments: Application to structures in the Salt Range and Potwar Plateau, Pakistan. Geological Society of America Bulletin 112, 351 – 363. DOI: 10.1130/0016-7606.
Farzipour-Saein, A., Yassaghi, A., Sherkati, S., Koyi, H., 2009. Mechanical stratigraphy and folding style of the Lurestan region in the Zagros Fold–Thrust Belt, Iran. Journal of the Geological Society 166, 1101–1115. DOI: 10.1144/0016-76492008-162.
Motamedi, H., Sherkati, S., Sepehr, M., 2012. Structural style variation and its impact on hydrocarbon traps in central Fars, Southern Zagros folded belt, Iran. Journal of Structural Geology 37, 124-133. DOI: 10.1016/j.jsg.2012.01.021.
Pattinson R., Jazayeri B., 1972. Structural analysis of the Zagros anticlines. Iranian Oil Operating Companies, Report No. 1188.
Sherkati, S., Letouzey, J., 2004. Variation of structural style and basin evolution in the central Zagros (Izeh zone and Dezful Embayment), Iran. Marine and Petroleum Geology 21, 535–554. DOI:10.1016/j.marpetgeo.2004.01.007.
Sherkati, S., Letouzey, J., Frizon de Lamotte, D., 2006. The Central Zagros fold-thrust belt (Iran): New insights from seismic data, field observation and sandbox modeling. Tectonics 25, TC4007. DOI: 10.1029/2004TC001766.
Spratt, D.A., Dixon, J.M., Beattie, E.T., 2004. Changes in structural style controlled by lithofacies contrast across transverse carbonate bank margins Canadian Rocky Mountains and scaled physical models. In: McClay, K.R. (eds) Thrust tectonic and hydrocarbon systems. AAPG Memoir 82, 259–275.
Stewart, S., 1996. Influence of detachment layer thickness on style of thin-skinned shortening. Journal of Structural Geology 18/10, 1271-1274.