الگوی زایش و فرگشت حوضه‏ های کششی مرتبط با ادامه گسله اصلی جوان زاگرس در شمال‏ باختر ایران

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری، دانشگاه تربیت مدرس، تهران، ایران

2 دانشیار، دانشکده علوم زمین، دانشگاه تحصیلات تکمیلی علوم پایه، زنجان، ایران

3 پژوهشگر، گروه لرزه ‏زمین‏ساخت و زلزله‌شناسی، سازمان زمین‌شناسی کشور، تهران، ایران

4 استادیار، بخش زمین‌شناسی، دانشگاه تربیت مدرس، تهران، ایران

چکیده

گسله اصلی جوان زاگرس یک سامانه گسله بزرگ است که در مرز شمالی زاگرس و مرز جنوبی ایران‏ مرکزی قرار گرفته است. هدف اصلی این بررسی توصیف هندسه و کینماتیک امروزی ادامه ناشناخته گسله اصلی جوان زاگرس در شمال باختری ایران و جنوب شرق آناتولی است. ما سازوکار امروزی گسله‌ها را از بررسی تصویرهای ماهواره‏ای و تلفیق آنها با برداشت‌های ساختاری میدانی، داده‌های ریخت‏‌زمین‏‌ساختی و نیز نتایج حاصل از وارون‌سازی داده‌های سازوکار کانونی زمین‌لرزه‌ها تعیین کرده‌‏ایم. سامانه‌ی گسله اصلی جوان زاگرس از پیرانشهر به‌سوی شمال و در راستای شاخه‏‌ای از زمین‌درز نئوتتیس، در مرز ایران- آناتولی خاوری، ادامه می‌یابد و در شمال‌ باختر با سامانه‌ی گسله‏‌های NE-SW چپ‏‌بر خوی- بسکل (در جنوب باختر آناتولی) پایان می‏‌پذیرد. سامانه گسله شناسایی شده، یک سامانه‌ی تراکششی راست‏‌بر است که در دل خود رژیم‌های تنش محلی راستالغز و کششی محض ایجاد کرده‌ است. دسته‌ای از حوضه‌‏های کششی، در خمش‏‌های گسلی یا در پهنه‌های میان تکه گسله‏‌های هم‌پوش راست‌پله راست‌بر ایجاد شده‌اند. با ورود به پهنه برخورد سامانه راست‌بر گسله با سامانه‌ی چپ‌‏بر خوی- بسکل، برش راست‏‌بر میان ورقه‌ی عربی و ایران مرکزی با گسله‌های چپ‌‏بر سد می‌شود و حرکت رو به ESE ایران نسبت به آناتولی، سبب ایجاد حوضه‏‌های کششی شمالی- جنوبی می‌شود که با گسله‌های نرمال شمالی- جنوبی محدود می‌شوند. این کشش، مشکل فضا در حرکت میان شمال ‌باختر ایران و جنوب خاور آناتولی را حل کرده‌ است. این بررسی، اهمیت گسله‌های راستالغز را در ایجاد رژیم‌های تنش محلی و زمین‌ساخت ناحیه‌ای کششی در جایگاه‌های برخوردی با رژیم تنش چیره ترافشارش نشان می‌دهد.

کلیدواژه‌ها


عنوان مقاله [English]

Evolution pattern of pull-apart basins related to the continuation of the Main Recent Fault in NW Iran

نویسندگان [English]

  • Mehrdad Niassarifard 1
  • Esmaeil Shabanian 2
  • Shahryar Solaymani Azad 3
  • Saeed Madanipour 4
1 Ph.D. Student; Department of Geology, Tarbiat Modares University, Tehran, Iran
2 Associate Professor; Department of Earth Sciences, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan Iran
3 Researcher, Seismotectonics and Seismology Department, Geological Survey of Iran, Tehran, Iran
4 Professor Assistant; Department of Geology, Tarbiat Modares University, Tehran, Iran
چکیده [English]

The continental suturing in Zagros was mainly occurred between the Arabian Plate in the southeast and Central Iran in the northeast along the Main Zagros Thrust. During the Pliocene time, the suture zone was reorganized and the belt-parallel component of the Arabia – Central Iran convergence has been localized along the Main Recent Fault (MRF). The Main Recent Fault is a major active strike-slip fault system on the border between the northern Zagros belt and Central Iran. Both geometry and kinematics of the fault system is rather well known along its central part and at its SE termination, while its possible continuation to the northwest is ambiguous. Moreover, less regard has been paid to possible relationships between this major intracontinental fault system and other strike-slip faults in NW Iran – SE Anatolia. The aim of this study is to describe both the genesis and evolution of Quaternary extensional basins in relation with the present-day geometry and kinematics of the NW continuation of the Main Recent Fault between SE Anatolia and NW Iran. We have used a combined approach including fault-slip data analysis and tectonic geomorphology to investigate active faulting of the MRF in NW Iran. Our results indicate that, to the north of latitude 37°N (NW from Piranshahr town), the main zone of the Main Recent Fault continues northwards along a less known branch of the Neotethyan suture up to the sinistral Khoy – Baskale fault zone in SE Anatolia. The recognized fault network in addition to the well-known NW part of the Main Recent Fault is divided into three distinct southern, central and northern structural zones. The almost 200 km long active fault system affecting the central and northern structural zones is transtensional dextral in character and is constituted by several strike-slip and normal faults and fault zones. The structural linkages of different zones occur through direct structural connections or soft linking releasing fault relay zones between overlapping fault strands. Our results also reveal that the NW continuation of the MRF clearly terminates to a NE-striking sinistral fault zone. At that place, the intracontinental dextral shear dies out and active deformation is transferred to N-S normal fault zones at the intersection zone of the NNW-SSE dextral and NE-SW sinistral faults. The crustal-scale ESE extension induced to these N-S fault zones has produced elongated extensional basins which, in the west of Lake Urmia and SE of Lake Van, resolve the space problem at the termination of the intracontinental dextral shear. These large elongated extensional basins show significant differences in both geometry and structural pattern with respect to the usual pull-apart basins formed in releasing fault relay zones of the dextral Main Recent Fault. According to our observation, the Marivan, Piranshahr, and Sardasht tectonic depressions are among the pull-apart basins formed in this kind of fault relay zones, while the Silvana – Serow and Başkale depressions are the result of crustal extension at the end of the dextral system. Considering the evolution stage of all the investigated extensional basins, those are classified into three distinct groups of active, transitional and inactive basins. Active basins are undergoing active extension and deposition, while inactive basins are transected by shortcut strike-slip faults and have entered the erosional stage. Basins in the transitional stage are filled by recent deposits affected by retrogressive erosion and incision. Active extension ended in the mature basins due to a direct structural connection of the overlapping main fault segments through a shortcut fault zone.
This erosion – deposition balance in the extensional basins (whatever their genesis) suggests that the extensional basins are more evolved southwards along the Main Recent Fault implying a probable northwards propagation for the dextral fault system. The distribution pattern of extensional basins described in this study reveals the importance of strike-slip faulting in producing special tectonic geomorphology features that are usually seen in extensional tectonic settings, while a dextral transpression is prevailing over the region.

کلیدواژه‌ها [English]

  • Main Recent Fault
  • fault-slip data analysis
  • Strike-slip Fault
  • NW Iran
  • SE Anatolia
  • extensional basin
1. Thatcher, W. (1995) Microplate versus continuum descriptions of active tectonic deformation. J. Geophys. Res., 100, 3885-389411. 
2. Sylvester, A.G. (1988) Strike-slip faults. Geological Society of America Bulletin, 100, 1666-1703.
3. Aydin, A. and Nur, A. (1982) Evolution of pull-apart basins and their scale independence. Tectonics, 1, 91-105.
4. Dooley, T.P. and Schreurs, G. (2012) Analogue modelling of intraplate strike-slip tectonics: a review and new experimental results.  Tectonophysics, 574-575, 1-71.
5. Smit, J., Brun, J.-P., Cloetingh, S., and Ben-Avraham, Z. (2008) Pull-apart basin formation and development in narrow transform zones.
6. Bellier, O. and Sebrier, M. (1994) Relationship between tectonism and volcanism along the Great Sumatran Fault zone deduced by SPOT image analyses. Tecronophysics, 233, 215-231. 
7. Baniadam, F., Shabanian, E., and Bellier, O. (2020) The kinematics of the Dasht-e Bayaz earthquake fault during Pliocene-Quaternary: implications for the geodynamics of eastern Central Iran, Tectonophysics, 772, 228-218. 
8. Braud J. and Ricou, L.E. (1971) L'accident du Zagros ou Mainthrust, un charriage et un collissement, C. R. Ac. Sc., Paris, ser. D, CCLXXII, 203-206. 
9. Tchalenko, J.S. and Braud, J. (1974) Seismicity and structure of the Zagros: the Main Recent Fault between 33 and 35N. Phil. Trans. R. Geol. Soc. Lond., 277, 1-25. 
10. Talebian, M., Jackson, J. (2004) A reappraisal of earthquake focal mechanisms and active shortening in the Zagros mountains of Iran. Geophys. J. Int., 156, 506-526.
11. Motaghi, K., Shabanian, E., and Kalvandi, F. (2017) Underplating along the northern portion of the Zagros Suture Zone, Iran, Geophysical Journal International, 210(1), 375-389.
12. Jackson, J.A. (1992) Partitioning of strike-slip and convergent motion between E Arabia in eastern Turkey and Caucasus, J. Geophys. Res., 97, 12471-12479.
13. Copley, A. and Jackson, J. (2006) Active tectonics of the Turkish–Iranian plateau. Tectonics, 25, 1-19.
14. Talebian, M. and Jackson, J. (2002) Offset on the Main Recent Fault of NW Iran and implications for the late Cenozoic tectonics of the Arabia-Eurasia collision zone. Geophys. J. Int., 150, 422-439.
15. Authemayou, C., Chadon, D., Bellier, O., Malekzade, Z., Shabanian, E., and Abbassi, M. (2006) Late Cenozoic partitioning of oblique plate convergence in the Zagros fold-and-thust belt (Iran). Tectonics, 25, TC3002.
16. Mohajjel, M. and Rasouli, A. (2014) Structural evidence for superposition of transtension on transpression in the Zagros collision zone: Main Recent Fault, Piranshahr area, NW Iran. J. Struct. Geol., 62, 65-79.
17. Niasarifard, M., Ghorashi, M., and Talebian, M. (2003). New View on investigation of active tectonic in Piranshahr fault. 23th Geosciences congress, Geological Society of Iran, Tehran (in Persian).
18. Niasarifard, M. (2005) Investigation of Seismotectonics and Morphotectonics of South West and West of Uremia Lake (With Emphasis of Piranshahr and Salmas Faults). M.Sc. Thesis, Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran, 138p (in Persian).
19. Nowroozi, A.A. (1971) Seismo-tectonics of the Persian plateau, eastern Turkey Caucasus, and himdu-Kush regions. Bull. Seismol. Soc. Am., 61, 317-341.
20. Shabanian, E., Bellier, O., Abbassi, M.R., Siame, L., and Farbod, Y. (2010) Plio-Quaternary stress states in NE Iran: Kopeh Dagh and Allah Dagh Binalud mountain ranges, Tectonophysics,     480(1-4), 280-304. 
21. Agard, P., Omrani, J., Jolivet, L., and Mouthereau, F. (2005) Convergence history across Zagros (Iran): constraints from collisional and earlier deformation. Int. J. Earth Sci., 94 (3), 401-419.
22. Solaymani Azad, S., Philip, H., Dominguez, S., Hessami, K., Shahpasandzadeh, M., Foroutan, M., Tabassi. H., and Lamothe, M. (2015) Paleoseismological and morphological evidence of slip rate variations along the North Tabriz fault (NW Iran). Tectonophysics, 640-641, 20-38.
23. Solaymani Azad, S., Faridi, M., Shokri, M.-A., Sartipi, A., and Alikhanzadeh, R. (2015) New Results of Seismicity Atlas of Urmieh, NW Iran, Specialized Journal for Urmieh Lake, Geol. Surv. Iran (in Persian).
24. Taghipour, K., Khatib, M.M., Heyhat, M.R., Shabanian, E., and A. Vaezihir (2018) Evidence for distributed active strike-slip faulting in NW Iran: The Maragheh and Salmas fault zones, Tectonophysics, 742, 15-33.
25. Solaymani Azad, S., Nemati, M., Abbassi, M., Foroutan, M., Hessami, Kh., Dominguez, S., Bolourchi, M., and Shahpasandzadeh, M. (2019) Active-couple indentation in geodynamics of NNW Iran: Evidence from synchronous left- and right-lateral co-linear seismogenic faults in western Alborz and Iranian Azerbaijan domains. Tectonophysics, 754, 1-17.
26. Gaudemer, Y., Tapponnier, P., and Turcotte, D.L. (1989) River offsets across active strike-slip faults. Annales Tectonicoe, 3, 55-76.
27. Shabanian, E., Acocella, V., Gioncada, A., Ghasemi, H., and O. Bellier (2012) Structural control on volcanism in intraplate post collisional settings: Late Cenozoic to Quaternary examples of Iran and Eastern Turkey, Tectonics, 31(3), TC3013.
28. Karakhanian, A.S., et al. (2004) Active faulting and natural hazards in Armenia, eastern Turkey and northwestern Iran, Tectonophysics, 380, 189-219.
29. Carey-Gailhardis, E. andMercier, J.-L. (1987) A numerical method for determining the state of stress using focal mechanism of earthquake populations: application to Tibetan teleseisms and microseismicity of southern Peru. Earth Planet. Sci. Lett., 82,165-179.
30. Harvard catalogue available at http://www. globalcmt.org/CMTsearch.html.
31. ISC catalogue available at http://www.isc.ac.uk/ iscbulletin/search/bulletin.
32. Jackson, J. and McKenzie, D. (1984) Active tectonics of the Alpine-Himalayan Belt between western Turkey and Pakistan. Geophys. J. R. Astron. Soc., 77(1), 185-264
33. Karasözen, E., Nissen, E., Bergman, E.A., and Ghods, A. (2019) Seismotectonics of the Zagros (Iran) from orogen-wide, calibrated earthquake relocations. Journal of Geophysical Research: Solid Earth, 124. 
34. Angelier, J. and Mechler, P. (1977) Sur une méthode graphique de recherche des contraintes principales egalement utilisable en tectonique et en seismologie: la methode des diedres droits. Bull. Soc. Géol. France, 19(6), 1309-1318.
35. Carey-Gailhardis, E. and Vergely, P. (1992) Graphical analysis of fault kinematics and focal mechanisms of earthquakes in term of stress; the right dihedra method, use and pitfalls. Annales Tectonics, VI(1), 3-9.
36. Javidfakhr, B., Bellier, O., Shabanian, E., Ahmadian, S., and Saidi, A. (2011), Plio–Quaternary tectonic  regime changes in the transition zone between Alborz and Kopeh Dagh mountain ranges (NE Iran), Tectonophysics, 506, 86-108.
37. Lacombe, O. (2012) Do fault slip data inversions actually yield “paleostresses” that can be compared with contemporary stresses? A critical discussion. C. R. Geoscience, 344, 159-173.
38. Ghods, A., Shabanian, E., Bergman, E., Faridi, M., Donner, S., Mortezanejad, G., and A. Aziz-Zanjani (2015) The Varzaghan–Ahar, Iran, Earthquake Doublet (Mw 6.4, 6.2): implications for the geodynamics of northwest Iran, Geophys. J. Int., 203, 522-540.
39. Carey, E. (1979) Recherche des directions principales de contraintes associees au jeu d'une population de failles. Rev. Geol. Dyn. Geogr. Phys., 21, 57-66.
40. Allen, M.B., Mark, D.F., Kheirkhah, M., Barfod, D., Emami, M.H., and Saville, C. (2011) 40Ar/39Ar dating of Quaternary lavas in northwest Iran: Constraints on the landscape evolution and incision rates of the Turkish-Iranian Plateau. Geophys. J. Int., 185, 1175-1188.
41. Lechmann, A., Burg, J-P., Ulmer, P., Guillong, M., and Faridi, M. (2018) Metasomatized mantle as the source of Mid-Miocene-Quaternary volcanism in NW-Iranian Azerbaijan: Geochronological and geochemical evidence. Lithos, 304-307.