Structural assessment of the Bradost and Berat structures in Imbricate and High Folded zones—Iraqi Kurdistan Zagros belt

Abstract

The Bradost and Berat anticlines are located within the Imbricate and High Folded zones of the NW segment of the Zagros fold-thrust belt, respectively, in the Iraqi Kurdistan Region. Two balanced cross-sections were built across these two anticlines, based on the integration of geological observations, few new available seismic, and well data, in order to unravel changes in the studied fold and fault architectures, from the surface to subsurface. The study aims to understand the sequential evolution of the Bradost and Berat thrusted anticlines. The studied sections imply that the Berat structure represents thrust-related anticline with pop-up geometry, whereas the Bradost structure comprises combination of two different geometries and styles of deformation along strike at each of the segments. So, the Bradost structure appears as a positive flower structure in one of the segments and as a ramp-related anticline in another segment. This structural phenomenon suggests development of two different segments instead of one embryonic anticline in the Bradost structure, which were later connected via transverse Hadar-Bekhme basement fault, during a progressive lateral growth of the two segments. The shortening values that were accommodated by the thrusts are ~ 991 m and ~ 553 m at the Bradost and Berat structures respectively. This variation in shortening is due to intensity of thrusting process which is higher in the Bradost structure than that in the Berat. The current study suggests that the underlying duplex structures below both Berat and Bradost structures are primarily responsible for the accommodation the potential uplifting of the studied structures, rather than the imbricate thrust system. Based on the obtained deformed geometry of the folds from the cross sections, the studied structures were decoupled within the Upper Paleozoic Ora Shale Formation. The overall deformed geometry of the cross sections indicates combination of thin- and thick-skinned deformation.

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Acknowledgements

The authors thank the Ministry of Natural Resources of the Kurdistan Regional Government for providing a few seismic and a well data. The constructive review and useful comments of two anonymous reviewers that helped to improve the revised manuscript are sincerely acknowledged. The Arabian Journal of Geosciences’ Assistant Editor Tavani Stefano is thanked for valuable suggestions on the manuscript.

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Balaki, H.G.K., Omar, A.A. Structural assessment of the Bradost and Berat structures in Imbricate and High Folded zones—Iraqi Kurdistan Zagros belt. Arab J Geosci 12, 106 (2019). https://doi.org/10.1007/s12517-019-4251-1

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Keywords

  • Bradost and Berat structures
  • Flower structure
  • Shortening estimation
  • Detachment surface
  • Structural relief
  • Duplex structure