Document Type : Original Research Paper

Authors

1 Department of Economic Geology, Tarbiat Modares University, Tehran

2 Department of Geology, Faculty of science, Tarbiat Modares University, Tehran, Iran.

Abstract

Lower-red, Qom and Upper-red Formations with Pliocene conglomerates were all folded in Shurab syncline containing northwest-southeast axial trace in southeast Qom city. In the southeastern part of the northern limb of the Shurab syncline, gypsum and marl elastic units of the Qom Formation have played a detachment surface role against the most competent layers of the Upper-red Formation due to high competency contrast. Rock units of the Qom Formation were thickened and locally folded with about north-northeast orientation in the southeastern part of the northern limb of the Shurab syncline. The thickening and folding in this part of the Shurab syncline is interpreted as the shearing process which has been produced in a shear zone initiated between the detachment surface and the Qom fault segment in the northern part of the Shurab syncline that was activated by right-lateral strike-slip displacement of the Qom fault in post Miocene.

Keywords

Bahroudi, A., Koyi, H.A., 2003. Approach effect of spatial distribution of Hormuz salt on deformation style in the Zagros fold and thrust belt: an analogue        modelling approach. Journal of the Geological Society, v. 160, p. 719-733.##
Bahroudi, A., 2003. The effect of mechanical characteristics of basal decollement and basement structures on deformation of the Zagros basin, Apsala University, Ph.D thesis.##
 Berberian, M., 1976. Contribution to the seismotectonics of Iran (part2). Geological Survey of Iran, Report No. 39, pp: 518.##
 Costa, E., Vendeville, B.C., 2002. Experimental insights on the geometry and kinematics of fold-and-thrust belts above weak, viscous evaporatic decollement. Journal of Structural Geology, 24, 1729-1739.##
Costa, E., Vendeville, B.C., 2004. Experimental insights on the geometry and kinematics of fold-and-trust belts above weak, viscous evaporatic devolvement: reply to comments by Hemin Koyi and James Cotton. Journal of Structural Geology, 26, 2139–2143.##
Cotton, J.T., Koyi, H.A., 2000. Modeling of thrust fronts above ductile and frictional detachments: applications to structures in Salt Range and Potwar Plateau, Pakistan. Geological Society of America Bulletin 112, 351-368.##
Davis, M.G. and Engeder, T., 1985. The role of salt in fold-and-thrust belts. Tectonophysics, 119, 67-88.##
 Luja´na, M., Stortib, F., Balanya´a, J., Crespo-Blanca, A., Rossetti, F., 2003. Role of decollement material with different rheological properties in the structure of the Aljibe thrust imbricate (Flysch Trough, Gibraltar Arc): an analogue modelling approach. Journal of Structural Geology, 25, 867–881.##
 Nogol-sadat, M.A.A., & Almasian, M., 1993. Tectonic map of Iran, scale 1/1,000,000. ##
Safaei, H., Taheri, A. & Vaziri-moghaddam, H., 2008. Structural analysis and evolution of the Kashan (Qom – Zefreh) fault Central Iran. Journal of Applied Sciences, 1426-1434.##
Suppe, J., 1983. Principles of structural geology. Prentice-Hall. Inc., Englewood Cliff, New Jersey 07632. 537 pages.##
Vendeville, B. C., 1991. Thin-skinned compressionl structures above frictional-plastic and viscous decollement layer. Geological Society of America, Abstract with Programs.##