Document Type : Original Research Paper


1 Ph.D. Student, Department of Geology, Faculty of Earth science, Shahid Beheshti university, Tehran, Iran

2 Professor, Department of Geology, Faculty of Earth science, Shahid Beheshti university, Tehran, Iran

3 Associate Professor, Research Institute for Earth Sciences, Geological Survey of Iran (GSI), Tehran, Iran

4 P.h.D. Exploration directorate, NIOC, Tehran, Iran


The significance of mechanical stratigraphy of rocks in kinematics of folds has long been of interest to structural geologists. Parameters such as sedimentary facies variations and thickness of incompetent layers play major role in activity of these layers as detachment horizons. The purpose of this study is to investigate the role of mechanical stratigraphy on fold geometry in the Aghajari and Pazanan anticlines within the Dezful Embayment zone. For this purpose, we have used seismic profiles, stratigraphic data and petrophysical logs as well as the previous stratigraphic works in study area. Results show that the Garau Formation is the major intermediate detachment level in the Aghajari structure, and has a significant control on folding geometry of the competent sequences of the Fahliyan to Asmari Formations. The Dashtak Formation and other incompetent evaporatic Formations of Middle-Upper Jurassic also have been active in the Aghajari structure. In contrast, in most parts of the Pazanan structure, the Garau and the Jurassic Formations do not have appropriate mechanical properties to act as intermediate detachment levels due to their change into hemipelagic facies and limestone (Surmeh Formation) respectively. Based on the evidences, the facies change in the abovementioned Formations occurs between the Pazanan and Aghajari anticlines. It seems that activity of the Hendijan-Izeh paleo-high also has some control on facies of the Garau Formation. Based on geometric characteristics and a geometric conceptual model provided for development of these structures, the folding style of the anticlines is suggested as an asymmetric faulted detachment fold type.


Main Subjects

Abdollahi Fard, I., Braathen, A., Mokhtari, M. and Alavi, S. A., 2006- Interaction of the Zagros Fold thrust belt and the Arabian type, deep-seated folds in the Abadan Plain and the Dezful Embayment, SW Iran. Petroleum Geoscience, v.12, p.347–62. doi: 10.1144/1354-079305-706.
Aqrawi, A. M., Goff, J. C., Horbury, A. D. and Sadooni, F. N., 2010- The Petroleum Geology of Iraq. Scientific Press, p.423. ISBN: 978-0-901360-36-8.
Armstrong, F. C. and Oriel, S. S., 1965- Tectonic development of Idaho-Wyoming thrust belt. AAPG Bulletin, v.49, p.1847-1866.
Berberian, M. and King, G. C. P., 1981- Towards a paleogeography and tectonic evolution of Iran. Canadian J. of Earth Sciences, v.18, p.210–285.
Blanc, E. P., Allen, M. B., Inger, S. and Hassani, H., 2003- Structural styles in the Zagros simple folded zone, Iran. Journal of the Geological Society, v.160, p.401-412.
Bordenave, M. L. and Hegre, J. A., 2005- The influence of tectonics on the entrapment of oil in the Dezful Embayment, Zagros fold belt, Iran. Journal of Petroleum Geology, v.28, p.339–368.
Bordenave, M. L. and Huc, A.Y., 1995- The Cretaceous source rocks in the Zagros foothills of Iran. Revue de L'institut Français du Petrole, v.50, no.6, p.727-752.
Briggs, S. E., Davies, R.J., Cartwright, J. A. and Morgan, R., 2006- Multiple detachment levels and their control on fold styles in the compressional domain of the deepwater west Niger Delta. Basin Research, v.18, p.435-450.
Buchanan, P. G. and McClay, K. R., 1991- Sandbox experiments of inverted listric and planar fault systems. Tectonophysics, v.188, p.97-115.
Cooke, M. L., 1997- Predicting fracture localization in folded strata from mechanical stratigraphy and fold shape: case study of East Kaibab Monocline, Utah. International Journal of Rock Mechanics and Mining Sciences, v.34, p.56-63.
Corbett, K., Friedman, M. and Spang, J., 1987- Fracture development and mechanical stratigraphy of Austin chalk, Texas. AAPG Bulletin, v.71, p.17–28.
Dalton, T. J. S., Paton, D. A. and Needham, D. T., 2017- Influence of mechanical stratigraphy on multi-layer gravity collapse structures: insights from the Orange Basin, South Africa. Geological Society, London, Special Publications, v.438, p.211-228.
Dixon, J. M. and Liu, S., 1992- Centrifuge modelling of the propagation of thrust faults. In: McClay, K.R. (Ed.). Thrust Tectonics. Chapman & Hall, London, p.53-69.
Edgell, H. S., 1992- Basement tectonics of Saudi Arabia as related to oil field structures. Basement tectonics, 9, p.169-193.
Edgell, H. S., 1996- Salt tectonism in the Persian Gulf basin. Geological Society, London, Special Publications, v.100, p.129-151.
Erickson, S. G., 1996- Influence of mechanical stratigraphy on folding vs faulting. Journal of Structural Geology, v.18, p.443-450.
Falcon, N. L., 1974- Southern Iran: Zagros Mountains. In: Mesozoic-Cenozoic orogenic belts. Geological Society of London. Special Publication, Ed. by A.M. Spencer, p.199-212.
Ghanadian, M., Faghih, A., Grasemann, B., Abdollahie Fard, I. and Maleki, M., 2017- Analogue modeling of the role of multi-level decollement layers on the geometry of orogenic wedge: an application to the Zagros Fold–Thrust Belt, SW Iran. International journal of earth science, v.106, p.2837–2853.
Gross, M., Fischer, M., Engelder, T. and Greenfield, R., 1995- Factors controlling joint spacing in interbedded sedimentary rocks; integrating numerical models with field observations from the Monterey Formation, USA. In: Ameen, M.S. (Ed.). Fractography. Geological Society Special Publication, London, p.215-233.
Gwinn, V. E., 1964- hin-skinned tectonics in the Plateau and northwestern Valley and Ridge provinces of the central Appalachians. Geological Society of America Bulletin, v.75, p.863-900.[863:TTITPA]2.0.CO;2.
Harris, L. D. and Milici, R. C., 1977- Characteristics of thin-skinned style of deformation in the southern Appalachians, and potential hydrocarbon traps. United States: Geological Survey Professional Papers, v.1018, Washington, DC.
Harrison, J. C. and Bally, A. W., 1988- Cross-sections of the Parry Islands fold belt on Melville Island, Canadian Arctic Islands: Implications for the timing and kinematic history of some thin-skinned decollement systems. Bulletin of Canadian Petroleum Geology, v.36, p.311-332.
Iacopini, D. and Butler, R. W., 2011- Imaging deformation in submarine thrust belts using seismic attributes. Earth and Planetary Science Letters, v.302, p.414-422.
Kobraei, M., Rabbani, A. R. and Taati, F., 2017- Source rock characteristics of the Early Cretaceous Garau and Gadvan formations in the western Zagros Basin–southwest Iran. Journal of Petroleum Exploration and Production Technology, p.1-20.
Letouzey, J., Colletta, B., Vially, R. and Chermette, J. C., 1995- Evolution of salt-related structures in compressional settings. In: Jackson MPA, Roberts DG, Snelson S (eds.) Salt tectonics: a global perspective AAPG Memoir 65, p.41–60.
Mitra, S., 2002- Structural models of faulted detachment folds. AAPG Bulletin, v.86, p.1673–1694. doi: 10.1306/61EEDD3C-173E-11D7-8645000102C1865D.
Nemcok, M., Schamel, S. and Gayer, R., 2005- Thrustbelts: Structural Architecture, Thermal Regimes and Petroleum Systems. Cambridge University Press, Cambridge, p.541.
Pierce, W. G., 1966- Jura tectonics as a decollement. Geological Society of America Bulletin, v.77, p.1265-1276.[1265:JTAAD]2.0.CO;2.
Sepehr, M. and Cosgrove, J. W., 2004- Structural framework of the Zagros fold–thrust belt, Iran. Marine and Petroleum Geology, v.21, p.829–843.
Sepehr, M., 2001- The tectonic significance of the Kazerun Fault Zone, Zagros fold-thrust belt, Iran. PhD thesis, Imperial College, University of London.
Sepehr, M., Cosgrove, J. W., Moieni, M., 2006- The impact of cover rock rheology on the style of folding in the Zagros fold-thrust belt: Tectonophysics, v.427, p.265–281.
Setudehnia, A., 1978- The Mesozoic sequence in southwest Iran and adjacent area. Journal of Petroleum Geology, v.1, p. 3–42.
Sherkati, S. and Letouzey, J., 2004- Variation of structural style and basin evolution in the central Zagros (Izeh zone and Dezful Embayment), Iran. Marine and Petroleum Geology, v.21, p.535–554.
Stewart, S. A., 1996- Influence of detachment layer thickness on style of thin-skinned shortening. Journal of Structural Geology, v.18, p.1271-1274.
T’Hart, B., 1970- Tectonic framework and paleogeography of the agreement area. National Iranian Oil Company, Report 1179 (unpublished).
Takin, M., 1972- Iranian geology and continental drift in the Middle East. Nature, v.235, p.147-150.
Talbot, C. J., 1992- Centrifuged models of Gulf of Mexico profiles. Marine and Petroleum Geology, v.9, p.412-432.