Document Type : Original Research Paper

Authors

1 Islamic Azad University, Sciences and Researches Campus, Basic Sciences Faculty, Tehran , Iran.

2 Shahid Beheshti University, Earth Sciences Faculty, Tehran , Iran

3 Tarbiat Modarres University, Basic Sciences Faculty, Tehran, Iran.

Abstract

Fars region in southwest Iran lies at the Zagros foreland and is bounded to the north and east by the Zagros thrust, to the west by the Kazerun fault, and to the south by the HormozStrait and the Persian Gulf. Thrust faults and associated folds are the main structures in the Fars region. The structures are trending NW to SE, the same trends as in the Zagros fold- thrust belt. The structural analysis of four anticlines in the interior Fars region based on the interpretation of seismic reflection lines and construction of structural sections on the basis of well data and field measurements indicates that fault propagation folds and fault detachment folds can be distinguished taking into consideration the geometry of the folds and the fault-fold relations. Based on measured parameters, the Ghareh Bulagh anticline is consistent with a fault propagation structure, while the Derz and Shirkhan anticlines with fault detachment structures. According to seismic reflection profiles and structural cross sections, the Chahkileh antiform is converted to a syncline at depth. The extent of shortening, based on the balanced structural cross sections, has been calculated to be around 14 percent. 

Keywords

References
Berberian, M., 1995- Master blind thrust faults hidden under the Zagros folds, Active basement tectonics and surface morphotectonics. Tectonophysics. V.241, P.193-244.
Boyer, S. E. & Elliot, D., 1982- Thrust Systems., AAPG Bull, v 66, p 1196-1230.
Comby, O., Lambert,C. & Coajou, A., 1977- An approach to the structural Studies of the Zagros fold belt in the EGOCO Agreement Area , in Proceeding of the Second Geological Symposium of Iran , Tehran , pp.133-159.
Dahlstrom, C.D.A., 1969- Balanced cross sections., Can.J.Earth Sci, v.6, p.743-757.
Elliot, D., 1983- The construction of balanced cross-section: Journal of Structural Geology, v.5, p. 101.
Gibbs, A.D., 1983- Balanced cross-section construction from seismic sections in areas of extensional tectonics. Jl.Struct.Geol.5, p.153-160.
Gibbs, A.D., 1984 – Structural evolution of extensional basin margins . Journal of Geological Society of London.v.141; no.4; p.609-620.
Hossack, J.R., 1979- The use of balanced cross sections in the calculation of orogenic contraction: A review. Journal of Geological Society of London. 136, 705-711.
Jamison, W.R., 1987- Geometric analysis of fold development in overthrust terranes. Journal of Structural Geology v.9 , p.207-219.
MacClay, K., 2001- Advanced Structural Geology in Petroleum Exploration.
MacClay, K. & Whitehouse, P.S. & Dooley, T. & Richards M., 2004– 3D evolution of fold and thrust belts formed by oblique convergence. Marine and Petroleum Geology . Vol. 21 , Issue 7, p.857-877.
Marshak, S. & Woodward, N., 1988 -Basic Methods of structural geology. -(Introduction to cross section balancing).
Rich, J.L., 1934- Mechanics of low angle overthrust faulting illustrated by Cumberland thrust block, Virginia, Kentucky and Tennessee. Bull. Geol. Soc. Amer. 18, 1584-1596.
Rodgers, J., 1949– Evolution of thought on structure of middle and Southern  Appalachians :  AAPG , v.33 ; no.8 ; p. 1643-1654.
Rodgers, J., 1963– Mechanics of Appalachian forland folding in Pennsylvania and West Virginia AAPG Bulletin, v.47 ; no.8 ; p. 1527-1563.
Setudehnia, A., 1978- The Mesozoic sequence in southwest Iran and adjacent area. Journal of Petroleum Geology, 1 (1), 3-42.
Thorbojohnson , Land Dunne, W. M., 1997- Origin of a thrust related fold, geometric vs kinematic tests. Journal of structural geology. v.19, p. 303-314.
Wernicke, B. & Burchfiel, B.C., 1982- Modes of extensional tectonics. Jl. Structural Geology ,4,105-115.