Document Type : Original Research Paper

Authors

1 Ph.D. Student, Department of Geology, Tarbiat Modares University, Tehran, Iran

2 Associate Professor, Department of Geology, Tarbiat Modares University, Tehran, Iran

3 Assistant Professor, Department of Geology, Zanjan Advance Studies in Basic Science, Zanjan, Iran

Abstract

In the east of high Zagros – in Faraghan Anticline- sedimentary cover with more than 10 km thickness has decoupled from basement above the Hormuz salt and has deformed. Mention anticline is cut by High Zagros Fault. By attention to lack of paleostress study and kinematic interpretation on north east of Fars Arc structures, in this paper we reconstructed stress field and interoperated its role in evolution of Faraghan Anticline. Inversion method used for determination of reduced stress tensor parameters and discrimination faults of every brittle tectonic phase. Maximum shortening axis determined by using Stylolite's and attitude of Minimum main stress determined by using veins. The present stress field was calculated by inversion of earthquake focal mechanism data. According to our data and the deduced results,  some of veins developed with an N27° - 29°E direction of σ1 stress axis before late of middle Miocene (before folding and faulting). During the late Miocene, sedimentary cover deformed as detachment and faults related folds in a general compressional stress regime with an N27° - 29°E direction of σ1. The basement faults were reactivated during late Miocene- early Pliocene in a general strike slip regime with an N4°E direction of σ1 stress axis. The High Zagros Fault was reactivated at that time and cross- cuts the entire cover section and its associated structures. In the late Pliocene, direction of σ1 stress axis temporally changed to N025°W in strike slip tectonic regime. Strike- slip and reverse faults were reactived in new stress field. Earthquakes Focal mechanism data analysis indicate that direction of σ1 stress axis is N-S now.

Keywords

References
Ahmadhadi, F., Lacombe, O., Daniel, J. M., 2007- Early reactivation of basement faults in Central Zagros (SW Iran): evidence from pre-folding fracture populations in Asmari Formation and lower Tertiary paleogeography. In: Thrust Belts and Foreland Basins. Springer, 205-228
Ahmadhadi, F., Daniel, J. M., Azzizadeh, M. and Lacombe, O., 2008- Evidenceforpre- folding veindevelopmentintheOligo-Miocene Asmari Formation in the Central Zagros Fold Belt, Iran. Tectonics: 27(1), TC1016.
Angelier, J., 1979- Determination of mean principal directions of stresses for a given fault population. Tectonophysics: 56, 17- 26.
Angelier, J., 1984- Tectonic analyses of fault slip data sets. J. Geophys. Res. 89 (B7): 5835–5848.
Angelier, J., 1989- From orientation to magnitudes in paleostress determinations using fault slip data. J. Struct.Geol 11 (1/2): 37–50.
Angelier, J., 1990- Inversion of field data in fault tectonics to obtain the regional stress. III. A new rapid direct inversion method by analytical means. Geophys. J. Int 103: 363–376.
Angelier, J., 2002- Inversion of earthquake focal mechanisms to obtain the seismotectonic stress: a new method free of choice among nodal planes. Geophys. J. Int 150 (3): 588–609.
Aubourg, C., Smith, B., Bakhtari, H., Guya, N., Eshraghi, S. A., Lallemant, S., Molinaro, M., Braud, X. and Delaunay, S., 2004- Post-Miocene shortening pictured by magnetic fabric across the Zagros–Makran syntaxis (Iran). In: Sussman, A.J., Weil, A.B. (Eds.), Orogenic Curvature: Integrating Paleomagnetic and Structural analyses. Geol. Soc. Amer. Special Paper, Boulder, Colorado: 383, 17– 40.
Authemayou, C., Chardon, D., Bellier, O., Malekzadeh, Z., Shabanian, E. and Abbassi, M. R., 2006- Late Cenozoic partition- ing of oblique plate convergence in the Zagros fold and thrust belt (Iran), Tectonics 25, TC3002.
Bakhtari, H. R., Frizon de Lamotte, D. and Aubourg, C., 1998- Magnetic fabrics of Tertiary sandstones from the Arc of Fars (Eastern Zagros Iran). Tectonophysics: 284, 299–316.
Bayer, R., Chery, J., Tatar, M., Vernant, Ph., Abbasi, M., Masson, F., Nilforoushan, F., Doerflinger, E., Regard, V. and Bellier., O, 2006- Active deformation in Zagros–Makran transition zone inferred from GPS measurements. Geophysical Journal International 165: 373-381.
Berberian, M., 1995- Master blind thrust faults hidden under the Zagros folds : active basement tectonics and surface morphotectonic, Tectonophysics 241: 193-224.
Carey-Gailhardis, E. and Mercier, J. L., 1987- A numerical method for determining the state of stress using focal mechanism of earthquake populations: application to Tibetan teleseisms and microseismicity of southern Peru. Earth Planet. Sci. Lett 82: 165–179.
Delvaux, D., Moeys, R., Stapel, G., Petit, C., Levi, K., Miroshnichenko, A., Ruzchich, V. and San’kov, V., 1997- Paleostress reconstructions and geodynamics of the Baikal region, Central Asia, Part 2. Cenozoic rifting. Tectonophysics 282:1-38.
Delvaux, D., 2014- WINTENSOR, VERSION 5.0.5, Royal Musem for Central Africa, Tervuren, Belgium Dept. Geology- Mineralogy.
Hessami, K., Nilforoushan, F. and Talbot, C. J., 2006- Active deformation within the Zagros Mountains deduced from GPS measurements. J. Geol. Soc. (Lond.) 163: 143–148.
Javadifakhr, B., Bellier, O., Shabanian, E., Ahmadian, S. and Saidi, A., 2011- Plio–Quaternary tectonic regime changes in the transition zone between Alborz and Kopeh Dagh mountain ranges (NE Iran).
Lacombe, O., Amrouch, K., Mouthereau, F. and Dissez, L., 2007- Calcite twinning constraints on late Neogene stress patterns and deformation mechanisms in the active Zagros collision belt. Geology 35, 263–6.
Lacombe, O., Mouthereau, F., Kargar, S. and Meyer, B., 2006- Late Cenozoic and modern stress fields in the western Fars (Iran): implications  for the tectonic and kinematic evolution of Central Zagros. Tectonics  25, TC1003.
Martinez-Dıaz, J. J., 2002- Stress field variation related to fault interaction in areverse oblique- slipfault:the Alhamade Murciafault, Betic Cordillera, Spain, Tectonophysics 356: 291–305.
McQuarrie, N., Stock, J. M., Verdel, C. and Wernicke, B. P., 2003- Cenozoic evolution of Neotethys and implications for the causes of plate motionmols. Geophys. Res. Lett 30 (20).
Molinaro, M., Leturmy, P., Guezou, J. C., Frizon de Lamotte, D., Eshraghi, S. A., 2005- The structure and kinematics of the south-eastern Zagros fold thrust belt; Iran: from thin-skinned to thick-skinned tectonics. Tectonics 24, TC3007.
Mouthereau, F., Tensi, J., Bellahsen, N., Lacombe, O. Deboisgrollier, T. and Kargar, S., 2007- Tertiary sequence of deformation in a thin-skinned/thick-skinned collision belt: the Zagros Folded Belt (Fars, Iran). Tectonics, 26, TC5006, doi:10.1029/2007TC002098.of Taiwan, J. Struct. Geol: 28, 1977 – 1993. Pl. Sc., 34, 419-466.
Navabpour, P., Angelier, J. and Barrier, E., 2007- Cenozoic post-collisonal brittle tectonic history and stress reorientation in the High zagros Belt (Iran, Fars Province). Tectonophysics, 432: 101-131.
Navabpour, P., Angelier, J. and Barrier, E., 2008- Stress state reconstruction of oblique collision and evolution of deformation partitioning in W-Zagros (Iran, Kermanshah). Geophysical Journal International 175: 755-782.
Navabpour, P., Angelier, J. and Barrier, E., 2010- Mesozoic extensional brittle tectonics of the Arabian passive margin, inverted in Zagros collision (Iran, Interior Fars). Brittle tectonic reconstruction of palaeo-extension inherited from Mesozoic rifting in W-Zagros (Iran, Kermanshah). Journal of the Geological Society, London.
Navabpour, P. and Barrier, E., 2011- Palaeostress review of the Zagros fold-and thrust belt and tectonic implications. EGU General Assembly, Vienna, 3-8 April 2011.
Navabpour, P., Angelier, J. and Barrier, E., 2011- Brittle tectonic reconstruction of palaeo-extension inherited from Mesozoic rifting in W-Zagros (Iran-Kermanshah). Journal of the Geological Society, London.
Ortner, H., Retter, F. and Acs, P., 2002- Easy Handing of tectonic data: the programs Tectonics VP for Mac and Windows, Computer and Geosience 28: 1193-n 11200.
Ramsay, J. G. and Huber, M. I., 1983- The Techniques of Modern Structural Geology, 1; Strain Analysis: London, Academic Press, 258 p.
Shabanian, E., Bellier, O., Abbassi, M. R., Siame, L. and Farbod, Y., 2010- Plio–Quaternary stress states in NE Iran: Kopeh Dagh and Allah Dagh-Binalud mountain ranges. Tectonophysics 480: 280–304.
Shadmon, A., 2008- Stylolites, A diagnostic tool. Retrieved from www.litosonline.com/articles/73/ar730ue.shtml.
Talebian, M. and Jackson, J., 2004- A reappraisal of earthquake focal mechanisms and active shortening in the Zagros mountains of Iran. Geophys. J. Int. 156, 506–526.
Tavakoli Sherazi, S., 2012- The Geology of the High Zagros (Iran) Tectonic and Thermal Evolution during the Paleozoic, [PhD. Thesis]: University of Cergy-Pontoise, 234p.
Tavakoli, F., Walpersdorf, A., Authemayou, C., Nankali, H. R., Hatzfeld, D., Tatar, M., Djamour, Y., Nilforoushan, F., Cotte, N., 2008- Distribution of the right lateral strike– slip motion from the Main Recent Fault to the Kazerun Fault System (Zagros, Iran): Evidence from present-day GPS velocities, Earth Planet. Sci. Lett 275: 342–347.
Vernant, P., Nilforoushan, F., Hatzfeld, D., Abbassi, M. R., Vigny, C., Masson, F., Nankali, H., Martinod, J., Ashtiani, A., Bayer, R., Tavakoli, F. and Chery, J., 2004- Present-day crustal deformation and plate kinematics in the Middle East constrained by GPS measurements in Iran and northern Oman. Geophys. J. Int 157: 381–398.
Yamaji, A., Tomita, S. and Otsubo, M., 2005- Bedding tilt test for paleostress analysis. Journal of Structural Geology 27: 161-170.
Yamini-Fard, F., Hatzfeld, D., Tatar, M., Mokhtari, M., 2006- Microseismicity on the Kazerun fault system (Iran): Evidence of a strike-slip shear zone and a thick crust, Geophys166: 186-196