Document Type : Original Research Paper
Author
Department of Geology, Faculty of Earth Sciences, Shahid Chamran University of Ahvaz, Ahvaz, Iran
Abstract
In this research, using deformed chert nodules in the calcareous units of Sarvak Formation in Pyun anticline, quantitative strain values in different parts of this anticline have been investigated. In a perpendicular fold axis survey, the anticline was divided into seven different areas. At least 40 nodules were measured in each area and finite strain analysis was carried out using Rf/Ø and polar methods. The results of strain studies show an increase mode in strain values from the fold limbs (Rs = 1.7) to the fold hinge (Rs = 2.9). Kinematic vorticity analysis shows the range between 0.68<Wk<0.91 and the effect of both simple and pure shear strain components and the occurrence of the strain partitioning in the Pyun anticline. The amounts of kinematic vorticity number indicate the increase of pure shear strain components in the hinge of anticline and the predominance of simple shear strain components in the limbs of the Pyun anticline. According to the results of strain analyses the amounts of bulk shortening was estimated about 47- 50 percent in the Pyun anticline.
Keywords
Main Subjects
Aghanabati, A., 2014. Geology of Iran. Samar press, 640p.(In Persian).
Alavi, M., 1994. Tectonics of the Zagros orogenic belt of Iran: new data and interpretation. Tectonophysics 229, 211–238, doi: 10.1016/0040-1951(94)90030-2.
Alavi, M., 2004. Regional stratigraphy of the Zagros fold-thrust belt of Iran, and its proforeland evolution. American Journal of Science 304,1–20, doi: 10.2475/ajs.304.1.1.
Alavi, M., 2007. Structures of the zagros fold-thrust belt in Iran. American journal of science, vol. 307, 1064-1095.
Al-Azzawi, N. K., 2008. Local Shortening of Folds and Detachment Surface Depth with Examples from the Foreland Belt of Iraq. Iraqi Journal of Earth Sciences- Vol. 8. No. 1- May.
Antonellini, M., Del Sole, L., and Mollema, P.N., 2020. Cherts nodules in plagic limestones as paleo-stress indicators: A 3D geomechanical analysis. Journal of Structural Geology 132: 103979.
Azhdari, A., Abiyat, A., Judaki, M., 2018. Geological map of Khozestan province 1/50000. Geological survey of Iran. .(In Persian).
Bailey, C.M., Gilmer, A.K., and Marquis, M.N., 1999. A tale of two shear zones: the vorticity and strain path of two greenschist facies shear zones, Geological Society of America Abstracts with Programs 31 (7), 59.
Berberian, M., 1995. Master ‘blind’ thrust faults hidden under the Zagros folds: active basement tectonics and surface morphotectonics, Tectonophysics, 241, 193–224.
Berberian, M., and King, G.C.P., 1981. Towards a paleogeography and tectonic evolution of Iran. Canadian Journal of Earth Sciences 18, 210–265.
Blanc, E.J.P., Allen, M.B., Inger, S., Hassani, H., 2003, Structural styles in the Zagros Simple Folded Zone, Iran. Journal of Geological Society 160: 401–412. doi:10.1144/0016-764902-110.
Darvishzadeh, A., 2006. Geology of Iran: stratigraphy, tectonic, metamorphism and magmatism. Amirkabir press, 436p. .(In Persian).
Dunnet, D., 1969. A technique of finite strain analysis using elliptical particles. Tectonophysics 7: 117–136.
Falcon, N.L., 1969. Problems of the relationship between surface structures and deep displacements illustrated by the Zagros range. Geological Society of London. Spec. Pub. 3, 9–22.
Fossen, H., 2010. Structural geology, Cambridge University Press, 481p.
Fossen, H., 2016. Structural Geology, 2nd edn. Cambridge University Press, Cambridge.
Frehner, M.D., and Grasemann, B., 2012. Mechanical versus kinematical shortening reconstructions of theZagros High Folded Zone (Kurdistan region of Iraq), Tectonics, 31, TC3002, doi:10.1029/2011TC003010.
Fry, N., 1979. Random point distribution and strain measurements in rocks. Tectonophysics 60: 89–105.
Galvez, R., and Orozco, M., 1974. Strain determinations using deformed Radiolaria. Malaguide Complex, Southern Spain. Acta Geologica Hispanica 14: 129-134.
Galvez, R., and Orozco, M., 1979. Strain determinations using deformed Radiolaria. Malaguide Complex, Southern Spain. Acta Geologica Hispanica 14: 129-134.
Haynes, S.J., and McQuillan, H., 1974. Evolution of the Zagros Suture zone, southern Iran. Geological Society of America Bulletin 85: 739–744.
Imber, J., Perry, T, Jones, R., and Wightman, R.H., 2012. Do cataclastic deformation bands form parallel to lines of no finite elongation (LNFE) or zero extension direction? Journal of Structural Geology 45:158–172.
Jackson, J., Haines, J., and William, H., 1995. The accommodation of Arabian-Eurasia plate convergence in Iran. Journal of Geophysical Research 100: 15205-15219.
Jackson, J.A., and McKenzie, D.P., 1984. Active tectonics of the Alpine–Himalayan Belt between Western Turkey and Pakistan. Geophysical Journal of the Royal Astronomical Society 77, 185–284.
Jessup, M.J., Law, R.D., Frassi, C., 2007. The rigid grain net (RGN): an alternative method for estimating mean kinematic vorticity number (Wm). Journal of Structural Geology 29: 411–421.
Keshavarz, S., and Faghih, A., 2020. Heterogeneous sub-simple deformation in the Gol-e-Gohar shear zone (Zagros, SW Iran): Insights from microstructural and crystal fabric. International Journal of Earth Sciences 109: 421- 438.
McQuarrie, N., 2004. Crustal scale geometry of the Zagros fold–thrust belt, Iran. Journal of Structural Geology 26: 519–535.
Means, WD., Hobbs, B.E., Lister, G.S., and Williams, P.F., 1980. Vorticity and noncoaxiality in progressive deformations. Journal of Structural Geology 2:371–378.
Molinaro, M., Zeyen, H., and Laurencin, X., 2005. Lithospheric structure beneath the southeastern Zagros Mountains, Iran: Recent slab break-off? Terra Nova 17, 1–6. doi:10.1111/j.1365-3121.2004.00575.x.
Mouthereau, F., Lacombe, O., and Verges, J., 2012. Timing, strain distribution and the dynamics of Arabia/Eurasia plate convergence. Tectonophysics 532–535: 27–60.
Partabian, A., and Faghih, A., 2021. Doming along the Zagros transpression zone, SW Iran: insights from microstructural analysis of heterogeneous deformation. Arabian Journal of Geosciences 14: 1-19.
Passchier, C.W., 1988. Analysis of deformation paths in shear zones. Geologische Rundschau 77: 309-318.
Perry, J.T., and Setudehnia, A., 1966. Geological map of Kuh-e Asmari 1/100000. National Iranian oil company.
Ramsay, J.G., 1967. Folding and Fracturing of Rocks. McGraw-Hill, New York, 568p.
Ramsay, J.G., and Huber, M.I., 1983. The Techniques of Modern Structural Geology. Strain Analysis, Academic Press, London, 1: 307p.
Samani, B., 2013. Quartz c-axis evidence for deformation characteristic in the Sanandaj-Sirjan belt Iran. Journal of African Earth Sciences 81: 28-34.
Samani, S., Faghih, A., 2014. Finite strain analysis in the Seydan anticline using ammonoid spiral shells, Zagros, Iran. Journal of African Earth Sciences 90: 25-30.
Samani, S., Faghih, A., and Grasemann, B., 2019. Strain pattern and vortisity analysis of deformed conglomerate in the Heneshk area within the Sanandaj-Sirjan metamorphic belt, Zagros Mountain, Iran. International Journal of Earth Sciences 109: 145-157.
Sarkarinejad, K., 2007. Quantitative finite strain and kinematic flow analyses along the Zagros transpression zone, Iran. Tectonophysics 442: 49–65.
Sarkarinejad, K., and Goftari, F., 2019. Thick-skinned and thin-skinned tectonics of the Zagros orogen, Iran: Constraints from structural, microstructural and kinematics analyses. Journal of Asian Earth Sciences 170, 249-273.
Sarkarinejad, K., Faghih, A., and Grasemann, B., 2008. Transpressional deformations within the Sanandaj–Sirjan Metamorphic Belt (Zagros Mountains, Iran). Journal of Structural Geology 30: 818–826.
Sarkarinejad, K., Keshavarz, S., Faghih, A., and Samani, B., 2016. Kinematic analysis of rock flow and deformation temperature of the Sirjan thrust sheet, Zagros Orogen, Iran. Geological Magazine 154 (1):147-156.
Sarkarinejad, K., Partabian, A., Faghih, A., and Kusky, T. M., 2012. Usage of strain and vorticity analyses to interpret large-scale fold mechanisms along the Sanandaj–Sirjan HP-LT metamorphic belt, SW Iran. Geological Journal, 47(1), 99-110.
Sarkarinejad, K., Samani, B., Faghih, A., Grasemann, B., and Moradipoor, M., 2010. Implications of strain and vorticity of flow analyses to interpret the kinematics of an oblique convergence event (Zagros Mountains, Iran). Journal of Asian Earth Sciences 38, 34–43.
Sherkati, S., and Letouzey, J., 2004. Variation of structural style and basin evolution in the central Zagros (izeh zone and Dezful Embayment), Iran. Marin and Petroleum Geology 21:535-554.
Sherkati, S., Molinaro, M., Frizon deLamotte, D., and Letouzey, J., 2005. Detachment folding in the Central and Eastern Zagros fold-belt (Iran): salt mobility, multiple detachments and late basement control. J.Struct. Geol. 27:1680–1696.
Simpson, C., and De Poar, D.G., 1997. Strain and kinematic analysis in general shear zones, Journal of Structural Geology, 15: 1–20.
Stöcklin, J., 1968. Structural history and tectonics of Iran. A review. American Association of Petroleum Geologists Bulletin 52: 1229–1258.
Talebian, M., and Jackson, J., 2002. Offset on the Main Recent Fault of NW Iran and implications for late Cenozoic tectonics of the Arabia–Eurasia collision zone. Geophysical Journal International 150: 422–39.
Tavakkoli, R., Sarkarinejad, K., Keshavarz, S., and Hosseini, S.R., 2022. Strain geometry and vorticity analysis of the deformed radiolarian rocks in the Abade-Tashk area, the Zagros suture zone, Iran. Journal of Earth Science 33:525-540.
Tikoff, B., and Teyssier, C., 1994. Strain and fabric analysis based on porphyroclast interaction. Journal of Structural Geology 16: 477-492.
Twiss, R.J., and Moores, E.M., 2004. Structural Geology second edition, W.H. Freeman and Company, New York, 552 p.
Twiss, R.J., and Unruh, J.R., 1998. Analysis of fault slip inversion: Do they constrain stress or strain? Journal of Geophysical Research 103: 12205-12222.
Vernant, P., Nilforoushan, F., Hatzfeld, D., Abbasi, M.R., Vigny, C., Masson, F., Nankali, H., Martinod, J., Ashtiani, A., Bayer, R., Tavakoli, F., and Chery, J., 2000. Present-day crustal deformation and plate kinematics in the Middle East constrained by GPS measurement in Iran and northern Oman. International Journal of Geophysics 157: 381–398.
Vitale, S., and Mazzoli, S., 2008. Heterogeneous shear zone evolution: the role of shear strain hardening/softening. Journal of Structural Geolology 30:1383–1395.
Vitale, S., Mazzoli, S., 2008. Heterogeneous shear zone evolution: the role of shear strain hardening/softening. Journal of Structural Geology 30:1383–1395.
Vollmer, F.W., 2011. EllipseFit 2.0. http://www.frederickvollmer.com/ellipsefit/.
Wallis, S.R., 1992. Vorticity analysis in a metachert from the Sanbagawa belt, SW Japan. Journal of Structural Geology 14: 271–280.
Xypolias, P., 2010. Vorticity analysis in shear zones: Areview of methods and applications, Journal of Structural Geology 42: 1-21.
Xypolias, P., Doutsos, T., 2000. Kinematics of rock flow in a crustal-scale shear zone: implication for the rogenic evolution of the southwestern Hellenides. Geological Magazine 137, 81–96.
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