The upper plate of the Arabia-Eurasia collision zone experienced orogen-perpendicular to orogen-parallel extension from 25–22 to 10–9 Ma. Although such an extension occurred during widespread collisional deformation, it is not clear if it is a local feature or if represents a major phase of upper plate extension. In this study we combine anisotropy of magnetic susceptibility (AMS) with fault kinematic analysis and sedimentologic data from 16.2- to 7.6-My-old deposits of the Upper Red Formation of the intermontane Tarom Basin (NW Iran). These strata present syndepositional, normal faults and offer the possibility to gain new insights into the spatial extent of such a Miocene extension. AMS data from the central and northern sectors of the basin document a tectonic fabric with a magnetic lineation parallel to the strike of the orogen, suggesting a compressional tectonic overprint. Conversely, the southern margin of the basin presents a purely sedimentary magnetic fabric despite a ~NE–SW orogen-perpendicular extension. This suggests that basin formation was not driven by extensional tectonics. Rather, the normal faults are gravity instabilities induced as also documented by coeval landslide deposits. This allows concluding that the orogen-perpendicular extension observed in few sectors of the collision zone is not regionally pervasive and hence it is not controlled by large-scale processes. Combined, our results indicate that if orogen-parallel extension associated with tectonic denudation and metamorphic core complex development occurred in certain sectors of the collision zone (Takab complex), it must have ended before 19–16 Ma, when widespread upper plate contractional deformation started.
Bibliographical noteFunding Information:
This study is part of the PhD thesis of MP at the University of Roma Tre (PhD program Cycle XXXII) and was supported by the PhD School of Roma Tre, the MIUR (Ministry of Education University and Research; Grant Rita Levi Montalcini and Prin_2017 20177BX42Z to PB and PRIN_2015 # 20158A9CBM_002 to MM), the DFG (German Science Foundation; grants DFG BA 4420/2-1 and BA 4420/2-2 to PB) and the DAAD (German Academy Research Service, grant to GH). The authors declare no financial or other conflicts of interest. The source of softwares (Anisoft and Daisy), the analysed data of anisotropy of magnetic susceptibility (AMS) samples and structural data/synsedimentary normal faults used to produce the results in this work and also raw AMS data from Mattei et al, 2017 used to compare with our data are available at https://data.mendeley.com/drafts/skwb6dtmgc/ reserved DOI: 10.17632/skwb6dtmgc.1. We thank the Editor Ibrahim Uysal for his assistance and suggestions and we are grateful to two anonymous reviewers for the constructive comments. The authors would also like to warmly thank to Prof. Bruce Moskowitz for his effective comments on the manuscript. MP is very grateful to Dr. Andrew (Andy) Wickert for logistical support in Minneapolis during the visit to the Institute for Rock Magnetism (IRM).
© 2021 Elsevier Ltd
- Anisotropy of Magnetic Susceptibility (AMS)
- Arabia-Eurasia collision zone
- Orogen-parallel extension
- Orogen-perpendicular extension
- Synsedimentary normal faults
- Tarom intermontane basin