مدل‌سازی آزمایشگاهی برهم‌کنش گسل‌ها در تکامل ساختاری تاقدیس‌های رگ سفید و تنگو (جنوب غرب ایران)

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه زمین‌شناسی، دانشکده علوم، دانشگاه بیرجند، بیرجند، ایران

2 گروه زمین شناسی، دانشکده علوم، دانشگاه بیرجند، بیرجند، ایران

چکیده

در فروبار دزفول جنوبی با توجه به توالی فاز­های دگرشکلی زاگرس و رخداد وارونگی تکتونیکی در گسل­ راندگی رگ سفید و همچنین تجدید فعالیت گسل­ پی سنگی هندیجان، بر هم­کنش عمودی بین گسل­ها در پیش بوم زاگرس اتفاق افتاده است؛ که این اثر متقابل تاثیراتی مهم بر الگوی ساختاری و تشکیل تاقدیس­های رگ سفید و تنگو دارد. فاز چین خوردگی اصلی در پیش بوم زاگرس و در تاقدیس­ رگ سفید در پلیوسن رخ داده است. جهت مدل­سازی آزمایشگاهی تکامل تکتونیکی، با توجه به محاسبه میزان کوتاه­شدگی عمود بر بخش مرکزی تاقدیس رگ سفید، با اعمال فشردگی به میزان 16 درصد و با حرکت فک­های متحرک دستگاه برش با سرعت ثابت، وارونگی تکتونیکی و تبدیل حرکت از کشش به راندگی در گسل رگ سفید سبب می­شود توالی لایه­ها دگرشکل شوند و چین خوردگی وابسته به گسل در تاقدیس رگ سفید تشکیل گردد. با ورود جبهه دگرشکلی زاگرس به پیش بوم منطقه کوهزایی در پلیوسن، علاوه بر برخاستگی تاقدیس تنگو در راس گسل هندیجان، محور تاقدیس رگ سفید به علت حرکت امتداد لغز راستگرد در گسل هندیجان، به میزان 30 درجه به صورت ساعتگرد می­چرخد. مدل­سازی ما نشان می­دهد که دلیل طول موج بیشتر بخش باختری تاقدیس رگ سفید به علت ضخامت زیاد لایه نمکی سازند گچساران و همچنین مقدار بالای نسبت  ضخامت لایه نامقاوم به لایه مقاوم است که در اثر واقع شدن بخش باختری تاقدیس رگ سفید در یک پهنه گسلی راستگرد و چرخش ساختاری حاصل از آن، پهن شدگی و افزایش طول موج تاقدیس تسهیل شده است.

کلیدواژه‌ها


عنوان مقاله [English]

Analog modeling of faults interaction in the structural evolution of the Rag Sefid and Tango anticlines (SW Iran(

نویسندگان [English]

  • Mehdi Yousefi 1
  • Seyed Morteza Moussavi 2
  • Mohammad Mehdi Khatib 2
1 Department of Geology, Faculty of Science, University of Birjand, Birjand, Iran
2 Department of Geology, Faculty of science, University of Birjand
چکیده [English]

Extended abstract
Introduction
The subduction systems are located in the continental collision phase. Due to the tectonic regime reversion from the tensile phase to the compressive phase and due to the reactivation of the normal and transverse basement faults, constitute folded belts that are in their tectonic evolution, have experienced multiple fault interactions. Therefore, based on the angle of post-collision shortening axis, relative to each of these old basement faults, their reactivation in the form of thrust or strike-slip components and their effects on the structural pattern of the folds, are justified. In the Zagros foreland, there are several fault lineaments with different trends and mechanisms. They have been reactivated during the collision phase of the Iranian and Arabian sheets. The present study tries to show the effect of the Zagros thrust faults and the Arabian strike slip faults interaction on the development and structural evolution of the Rag Sefid and Tango anticlines using analog modeling.
Materials and Methods
In order to model the interaction of basement faults in the South Dezful embayment, first, in accordance with the structural realities of the region, the topography of the basement is simulated using the cutting of wooden boards. The arrangement and cutting of the boards are according to the slope of the Rag Sefid thrust fault. First the wooden board is cut at an angle of 47 degrees. Also, considering that about one third of the Rag Sefid anticline has an axial curvature, and due to the slope of approximately 80 degrees at Hendijan fault, which is perpendicular to the Rag Sefid fault, the wooden board is cut into two unequal parts with an 80-degree slope. According to the interpretation of reflective seismic sections and drilled well data, the stratigraphic sequences detectable in the southern Dezful embayment are Aghajari, mobile Gachsaran formation and Middle Resistance Group between Asmari to Gadvan, respectively. Therefore, in order to model these stone units, clay with a thickness of 3 and 2 cm was used for upper and middle resistant units, respectively. Also, in order to simulate the Gachsaran moving formation, a combination of sifted rock powder and 3 cm thick engine oil is used at the beginning of modeling.
Results and discussion
The northwest-southeast trend of Rag Sefid anticline located in Zagros foredeep, has been raised due to the Zagros orogenic phase in the Pliocene. After the collision of the plates from the Late Eocene onwards, in addition to folding on the northwest-southeast faults, the north-south basement faults during the Late Cenozoic have been reactivated by the entry of the Zagros deformation front into the study area. The reactivation of these faults has caused changes in sedimentary cover, such as facies change and sediment thickness as well as changes along the axis of surface anticlines. Oblique convergence after collision between Iran and the Arabian Plate has shortened the succession of the Zagros basement; so that the northwest-southeast longitudinal faults that were extensional at the time of the rift formation are now basement thrusts in this belt. The north-south faults, which have trends similar to those of the north-south basement fault in the eastern Arabian Block, are reactivated as a result of this compression.
Conclusion
Due to the general compression trend of N22E in southwestern Iran and the trend of the southern part of the Hendijan fault (N20E), the small-scale fold at the Tango anticline located on the Hendijan fault is due to the parallelism of this transverse fault and the overall compression direction. In contrast to the Rag Sefid anticline, where the trend of the main fault is approximately perpendicular to the direction of total compression (N100), a clear fold with large structural dimensions is created in the Rag Sefid anticline. Our results show that with the entry of the Zagros deformation front into the foreland of the orogenic region in the Pliocene, in addition to the Tango anticline rising at the top of the Hendijan fault, the Rag Sefid anticline has rotated axially by 30 degrees clockwise due to the movement of the right-hand slip in the Hendijan fault. Our modeling shows that the reason for the higher wavelength of the western part of the Rag Sefid anticline is due to the high thickness of the salt layer and also the high value of the ratio number. Due to the location of the western part of the Rag Sefid anticline in a right-sided fault zone and the resulting structural rotation, the widening and increasing wavelength of the anticline is facilitated.

کلیدواژه‌ها [English]

  • Fault interaction
  • Modeling
  • Rag Sefid anticline
  • Hendijan fault
-Abdollahi Fard, I., Braathen, A., Mokhtari, M. and Alavi, S.A., 2006. Interaction of the Zagros Fold thrust belt and the Arabian type, deep-seated folds in the Abadan Plain and the Dezful Embayment, SW Iran: Petroleum Geoscience, v. 12, p. 347-362.
-Agard, P., Omrani, J., Jolivet, L. and Mouthereau, F., 2005. Convergence history across Zagros (Iran): Constraints from collisional an earlier deformation: International Journal of Earth Science, v. 94, p. 401-419.
-Audet, P. and Burgmann, R., 2011. Dominant role of tectonic inheritance in supercontinent cycles: Natral Geoscience, v. 4, p. 184-187.
-Butler, R.W.H., Tavarnelli, E. and Grasso, M., 2006. Structural inheritance in mountain belts: an Alpine-Apennine perspective: Journal of Structural Geology, v. 28, p. 1893-1908.
-Burberry, C.M., 2015a. The effect of basement fault reactivation on the Triassic- Recent geology of Kurdistan, N Iraq: Journal of Petroleum Geology, v. 38 (1), p. 37-58.
-Del Ventisette, C., Montanari, D., Sani, F. and Bonini, M., 2006. Basin inversion and fault reactivation in laboratory experiments: Journal of Structural Geology, v. 28, p. 2067-2083.
-Dubois, A., Odonne, F., Massonnat, G., Lebourg, T. and Fabre, R., 2002. Analogue modelling of fault reactivation: tectonic inversion and oblique remobilization of grabens: J. Struct. Geol, v. 24, p. 1741-1752.
-Eisenstadt, G. and Withjack, M.O., 1995. Estimating inversion: results from clay models. In: Buchanan, J.G. and Buchanan, P.G. (Eds.), Basin Inversion, 88: Geological Society of London Special Publication, p. 119-136.
-Hessami, K., Koyi, K.A. and Talbot, C.J., 2001. The significance of strike-slip fauting in the basement of the Zagros fold and thrust belt: journal of petroleum geology, v. 24, p. 5-28.
-Huerta, A.D. and Harry, D.L., 2012. Wilson cycles, tectonic inheritance, and rifting of the North American Gulf of Mexico continental margin: Geosphere, v. 8, p. 374-385.
-Jolley, S.J., Fisher, Q.J. and Ainsworth, R.B., 2010. Reservoir compartmentalization: an introduction. In: Jolley, S.J., Fisher, Q.J., Ainsworth, R.B., Vrolijk, P.J. and Delisle, S).Eds.): Geological Society of London, v. 347, p. 1-8.
-Kattenhorn, S.A., Aydin, A. and Pollard, D.D., 2000. Joints at high angles to normal fault strike: an explanation using 3-D numerical models of fault-perturbed stress fields: Journal of Structural Geology, v. 22, p. 1-23.
-Koop, W. and Stoneley, R., 1982. Subsidence history of the Middle East Zagros basin, Permian to Recent: Philosophical Transactions of the Royal Society of London, v. 305, p. 149-168.
-Macedo, J. and Marshak, S., 1999. Controls on the geometry of fold-thrust belt salient: Geological Society of American Bulletin, v. 111(12), p. 1808-1822.
-Maerten, L., Gillespie, P. and Pollard, D.D., 2002. Effects of local stress perturbation on secondary fault development: Journal of Structural Geology, v. 24, p. 145-153.
-McMechan, M.E., 2012. Deep transverse basement structural control of mineral systems in the southeastern Canadian Cordillera. Canadian Journal of Earth Science, v. 49 (5), p. 693-708.
-Molliex, S., Bellier, O., Terrier, M., Lamarche, J., Martelet, G. and Espurta, N., 2010. Tectonic and sedimentary inheritance on the structural framework of Provence (SE France): importance of the Salon-Cavaillon fault: Tectonophysics, v. 501, p. 1-16.
-Panien, M., Schreurs, G. and Pfiffner, A., 2005. Sandbox experiments on basin inversion: testing the influence of basin orientation and basin fill: Journal of Structural Geology, v. 27, p. 433-445.
-Peacock, D.C.P., Nixon, C.W., Rotevatn, A., Sanderson, D.J. and Zuluaga, L.F., 2017- Interacting faults: Journal of Structural Geology, v. 97, p. 1-22.
-Sepehr, M. and Cosgrove, J.W., 2004. Structural framework of the Zagros fold-thrust belt, Iran: Marine and Petroleum Geology, v. 21, p. 829-843.
-Sherkati, S., Letouzey, J. and Frizon de Lamotte, D., 2006. The Central Zagros fold-thrust belt (Iran): New insights from seismic data, field observation and sandbox modeling: Tectonics, v. 25, p. 1-27.
-Soleimany, B. and Sàbat, F., 2010. Style and age of deformation in the Northwest Persian Gulf: Petroleum Geosciences, v. 15, p. 1-10. DOI: 10.1144/1354-079309-837.
-Twiss, R.J. and Moores, E.M., 1992. Structural Geology: W.H. Freedman & Company, New York, 532 p.
-Verges, J., Goodarzi, M.G.H., Emami, H., Karpuz, R., Efstathiou, J. and Gillespie, P., 2011. Multiple detachment folding in Pusht-e Kuh arc, Zagros: role of mechanical stratigraphy. In Thrust Fault Related Folding: American Association of Petroleum Geologists Memoir, v. 94, p. 1-26.
-Willingshofer, E., Sokoutis, D. and Burg, J.P., 2005. Lithospheric-scale analogue modelling of collision zones with a pre-existing weak zone. In: Gapais, D., Brun, J.P., Cobbold, P.R. (Eds.), Deformation Mechanisms, Rheology and Tectonics: from Minerals to the Lithosphere: Geological Society of London, Special Publication, v. 243, p. 277-294.