Document Type : Original Research Paper

Authors

Tectonic Group, Tarbiat Modares University, Tehran, Iran.

Abstract

Abundant chevron folds were produced in well-bedded red thin layers radiolarites in Kermanshah area. Various fold hinge area structures were produced due to competency contrast and change of thickness in radiolarian shale and thick-bedded limestone intercalation in radiolarite sequence. Different styles of folding exist in massive to thick-bedded limestone and shale where they are inter-bedded with radilarites. Unique thin layers of the radolarite layers were folded in parallel shape but change of folds shape and mechanism were produced where thick bedded limestone or thin layers of radiolarian shale intercalations exist. Fold accommodation faults were generated in cases during folding. Geometry and style of folding indicate that deformation in radiolarites was produced by parallel folding due to buckling mechanism with southwest vergence. Thrust faults were generated during later stages, displacing some parts of the folded radiolarites.

Keywords

References
Agard, P., Omrani, J., Jolivet, L., Mouthereau, F., 2005- Convergence history across Zagros (Iran): Constraints from collisional and earlier deformation, Int. J. Earth Sci., 94, 401 – 419, doi: 10.1007/ S00531-005-0481-4.
Alavi, M., 1994- Tectonics of the Zagros Orogenic belt of Iran: new data and interpretations. Tectonophysics 229, 211–238.
Bastida, F., Aller, J., Toimil, N. C., Lisle, R. J., Bobillo-Ares, N. C., 2007- Some consideration on the kinematics of chevron folds. Journal of Structural Geology, 29, 1185-1200.
Bechennec, F., Le Metour, J., Rabu, D., Bourdillon-de-Grissac, Ch., De Weaver, P., Beurrier, M., Villey, M., 1990- The Hawasina Nappes: stratigraphy, palaeogeography and structural evolution of a fragment of the south-Tethyan passive continental margin. In: Robertson, R.H.F., Searle, M.P., Ries, A.C. (Eds.), the Geology and Tectonics of the Oman Region, Geological Society of London. Special Publication, 49, pp. 213–223.
Berberian, M. and King, G. C. P., 1981- Towards a paleogeography and tectonic evolution of Iran, Canadian Journal of Earth Sciences, V. 18, pages, 210– 265.
Braud, J., 1987-  Paleogeographique, magmatique et structural de la region Kermanshah. Iran these the etate, universite de Paris farance, 489p. Bugq.j.p and cheng.GM, 1984- tectonic and structural zonation of southern Tibet, nature, 311:219-255.
Cooper, D. J. W., 1988-  Structure and sequence of thrusting in deep- water sediments during ophiolite emplacement in the south-central OmanMountains, J. Struct. Geol.10, 473-485.
Cooper, D. J. W., 1990-  Sedimentary evolution and palaeoceanographic reconstruction of the Mesozoic continental rise in Oman: evidence from the Hamrat Duru Group. In: Robertson, A.H.F., Searle, M.P., Ries, A.C. (Eds.), the Geology and Tectonics of the Oman Region. Special Publication-Geological Society of London, vol. 49, pp. 161– 168.
Coward, M., 1994 -  Inversion tectonics. In: Hancock, p. (Ed) Continental deformation. Pergamon press, p.421.
Dercourt, J., Ricou, L. E., Vrielynck, B., (Eds)., 1993-  Atlas Tethys plaeoenvironmental maps. Gauthier-Villars, 260 pp, 14 maps.
Dubey, A. K., Cobbold, P. R., 1977- Noncylindrical flexural slip folds in nature and experiment. Tectonophysics 38, 223-239.
Fluty, M. J., 1964 - The description of folds geological Society of London. 75, 461-492.
Fowler, T. J., Winsor, C. N., 1996 - Evolution of chevron folds by profile shape changes: comparison between multilayer deformation experiments and folds of the Bendigo-Castlemaine goldfields, Australia. Tectonophysics 258, 125-150.
Ghosh, S. K., 1968 - Experiments of buckling of multilayers which permit interlayer gliding. Tectonophysics, 6, 207-249.
Graham, G., 1980 - Ophiolites. In: Panayiotou, A. (Ed.), Proceedings International Ophiolite Symposium Cyprus 1979. Cyprus Geological Survey Department, pp. 414– 423.
Johnson, A. M., Ellen, S. D., 1974 - Theory of concentric, kink and sinusoidal folding introduction. Tectonophysics 21, 301-339.
Johnson, A. M., Honea, E., 1975 - A theory of concentric, kink, and sinusoidal folding and of monoclinal flexuring of compressible, elastic multilayers. Part III, transition from sinusoidal to concentric-like to chevron folds. Tectonophysics 27, 1-38.
Kazmin, V. G., Ricou, L. F., Sbortshikov, I. M., 1986 - Structure and evolution of the passive margin of the eastern Tethys.Tectonophysics 123, 153–179.
Mitra, S., 2002 - Fold-accomodation faults. AAPG bull. 86(4), 671-693.
Mohajjel, M., Fergosson, C. L., Sahandi, M. R., 2003 - Cretaceous–Tertiary convergence and continental collision Sanandaj–Sirjan Zone, western Iran Journal of Asian Earth Sciences 21, 397–412.
Paterson, M. S., Weiss, L. E., 1966 - Experimental deformation and folding in phyllite. Geological society of America Bullitin, Vol.77, pp 343-374.
Ramberg, H., 1963 - Strain distribution and geometry of folds. Upps Univ Geol Inst Bull 42:1–20.
Ramberg, H., 1964 - Selective buckling of composite layers with contrasted rheological properties. A theory for simultaneous formation of several orders of folds. Tectonophysics 1, 307-341.
Ramberg, I. B., Johnson, A. M., 1976 - Asymmetric folding in interbedded chert and shale of the Franciscan Complex, San FranciscoBay area, California. Tectonophysics 32, 295-320.
Ramsay, J. G., Huber, M., 1983 - The Techniques of Modern Structural Geology. Academic Press, v. 1, p. 1-308.
Ramsay, J. G., Huber, M., 1987 - The Techniques of Modern Structural Geology. Academic Press, v. 2, p .309-700.
Sherkati, S., Molinaro, M., deLamotte, D. F., Letouze., J., 2005 - Detachment folding in the central and eastern Zagros fold belt (Iran):salt mobility, multiple detachment, late basement control. Journal of Structural Geology, 27, 1680-1696
Twiss, J.  R., Moores, M., 1992 - Structural Geology. Academic Press, v. 2, p .1_532.
Yousefi, E., Friedberg, J. L., 1978- Aeromagnetic map of Iran, Quadrangle no.c6. Kermanshah.