Kharazmi Journal of Earth Sciences

Kharazmi Journal of Earth Sciences

Post Cretaceous Tectonic Evolution of Azadkuh Region in Central Alborz Mountains

Authors
Mohammad Akbar Barati
Ali Yassaghi
Saeed Madanipour
10.52547/gnf.6.1.41
Abstract
Azadkuh region located in Central Alborz Range and comprises Paleozoic to Cenozoic rock units. The Azadkoh Fault in the north and the TF4 Fault in the south bounded the region. This study aimed to investigate structural events in the region as a part of central Alborz since Cretaceous. Investigation of structural evidence shows several geological events in Cenozoic at this part of Central Alborz range. Cretaceous volcanic overlay the Triasic-Jurasic Shemshak Formation as angular unconformity. In addition, the Paleocene Fajan conglomerate as angular unconformity overlay the Cretaceous volcanic or older rocks. The presence of Cretaceous rocks and the Karaj Formation within the Eocene basin bounding faults in which syn-sedimentary faults developed demonstrate that the faults formed as normal kinematic acting as the basin bounding faults. Several evidence including high dip angle of the Azadkuh Fault, development of the TF3 Fault as the Azadkuh Fault backthrust in the fault hanging wall, thrust of the younger Cretaceous rocks over the older Triassic-Jurassic rocks, and formation of a pop-up structure in between the Azadkuh and TF3 faults might reflect the inverted normal nature for the faults. During Plio-Quaternary SW-ward movement of the Khazar Block with respect to Central Iran causes transpression tectonics in the region resulted in development of strike-slip faults and related structures that cross-cut the Azadkuh region inverted basin bounding faults.



Keywords
Central Alborz
Azadkuh region
Structural Inversion
transpression
Subjects
5. Alavi M., "Tectonostratigraphic synthesis and structural style of the Alborz mountain system in northern Iran", Journal of Geodynamics, V.21 (1996) 1– 33.
6. Allen M. B., M R. Ghassemi, M Shahrabi, M Qorashi., "Accommodation of late Cenozoic oblique shortening in the Alborz range, northern Iran", Journal of Structural Geology, 25 (2003a) 659 – 672.
7. Berberian M., "the southern Caspian: A compressional depression floored by a trapped, modified oceanic crust", Canadian Journal of Earth Sciences, v. 20 (1983)163–183.
8. Berberian M., and King G., "Towards a paleogeography and tectonic evolution of Iran", Canadian Journal of Earth Sciences, v. 18, No. 2 (1981) 210-265.
9. Coward M., "Inversion tectonics. In: Hancock, p. (Ed) Continental deformation, Pergamon press, (1994) p. 421.
10. Fossen H., Tikoff B., and Teyssier C., "Strian modeling of transpressional and transtensional deformation" Norsk Geologisk Tidsskrift, v. 74, no. 3 (1994) p. 134-145.
11. Fossen H., and Tikoff B., "Extended models of transpression and transtension, and application to tectonic setting", Geological Society, London, Special Publication, v. 135, no.1 (1998)15-33.
12. Jackson J., Priestley K., Allen M., and Berberian M., "Active tectonics of the South Caspian Basin", Geophysical Journal International, v. 148 (2002) 214–245.
13. Jones R. R., Holdsworth R. E., Clegg P., McCaffrey K., and Tavarnelli E., "Inclined transpression", Journal of Structural Geology, v. 26, no. 8 (2004) 1531-1548.
14. McClay K. R., and Buchanan P. G., "Thrust faults in inverted extensional basins. In: McClay, K.R.(Ed.), Thrust Tectonics. Chapman & Hall, London, (1992) 93–104.
15. Shahidi A., Barrie E., Brunet M. F., and Saidi A., "Tectonic evolution and Late Triassic- Middle Eocene extension in central Alborz, Iran", Geosciences, v. 17 (2008) 4-24.
16. Vincent S. J., Allen M. B., Ismail-Zadeh A. D., Flecker R., Foland K. A., and Simmons M. D., "Insights from the Talysh of Azerbaijan into the Paleogene evolution" (2005)
17. Yassaghi A., "The effect of deep-seated transverse faults on structural evolution of west-central Alborz mountains", Geophysical Research Abstracts, Vol. 7 (2005)
18. YassaghA., Naeimi A., "Structural analysis of the Gachsar sub-zone in central Alborz range; constrain for inversion tectonics followed by the range transverse faulting", International journal of earth sciences, 100, 6 (2011) 1237-1249.
19. Yassaghi A., Madanipour S., "Influence of a transverse basement fault on along strike variations in the geometry of an inverted normal fault: Case study of the Mosha Fault, Central Alborz Range, Iran", Journal of Structural Geology, 30, 12 (2008) 1507-1519.
20. Zanchi A., Berra F., Mattei M., Ghassemi M. R., Sabouri J., "Inversion tectonics in central Alborz, Iran", J. Structural Geology, (2006) 1-15.
21. Ziegler M. A., "Late Permian to Holocene paleofacies evolution of the Arabian Plate and its hydrocarbon occurrences", Geo Arabia, 6 (2001) 445-504.