Style and Timing of Folding and Faulting in the Mahneshan Basin and the Takab Metamorphic Complex

Document Type : Original Article

Authors

1 1- M.Sc. in Tectonics, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, Iran

2 Department of Earth Sciences, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, Iran

3 Assistant Professor, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, Iran

Abstract

 
Abstract
The Mahneshan sedimentary basin is one of the Cenozoic syntectonic basins in the Central Iran, which is located between the western Alborz Mountains and the Takab Complex. Our study area at the Mahneshan mainly includes Kahar Formation and granitic, gneissic and metamorphic units of the Takab complex and Cenozoic sedimentary and volcanic sequences including the Upper Red, Qom and Lower Red Formations. In this study, by combination of remote-sensing and extensive field mapping including fault kinematics, fold geometries, growth strata patterns and unconformities, a structural cross-section constructed across the Mahshan Basin and the Takab complex and geometric and kinematic relationships of the geological units were determined. According to the cross-section, the NW-trending Mahneshan fault zone show an almost pure reverse mechanism with a right-lateral strike-slip component. On the other hand, the NW-SE trending faults of Takab complex have right strike-slip mechanism. Fault systems with thrust and strike-slip kinematics have aligned almost parallel in the Mahneshan Basin and Takab Metamorphic complex that documents prominent strain partitioning in a transpressional deformation regime during post-Oligocene time. This structural model confirms hypothesis on strain partitioning documented in other studies for the Central Iranian Basin. Syntectonic growth strata development in the Lower Red Formation and also sedimentary unconformities and onlap of the Lower Red and Qom Formations on older sedimentary and metamorphic units in the Takab complex and Mahnashan basin suggests that their deformation initiated during the latest Oligocene, which can be attributed to the onset of Arabia–Eurasia collision and exhumation of the western Alborz Mountains.

Keywords

Journal of Tectonics
Volume 3, Issue 11
October 2020
Pages 60-70

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