The effects of wrench-dominated basement-involved faults on folding of overlying strata in the Bahregansar anticline, western Persian Gulf, Iran

Abstract

Basement-involved fault geometry and kinematics has a systematic effect on the structural style of the tectonic setting. In this study, 2D and 3D seismic datasets, well data as well as thickness and depth maps were utilized to consider and reconstruct the characteristics and effects of the wrench-dominated basement-involved fault underlying the Bahregansar anticline, which is a gentle, elongated and NW–SE-trending structure in the NW Persian Gulf, on the nature of its folded strata. Moreover, using the 2D sequential restoration, the deformation of the basement structural features was modelled and analysed for its influence on the reactivation of faulting. The results show that the major basement-involved fault, called the Hendijan–Bahregansar–Nowrooz Fault (HBNF), extends along the NE–SW-trending orientation and consist of several key anticlines. The structural evolution of the Bahregansar anticline has been deeply affected by Turonian folding phase and Pliocene Zagros orogeny associated with the HBNF. In the Upper Cretaceous, the HBNF propagated upward through the overlying sedimentary sequences when the inherited normal fault contractionally reactivated in the sinistral-reverse sense as the transpression zone in response to the Neo-Tethys oceanic plate subduction under the Eurasian plate. In this regard, the NNE–SSW-trending Bahregansar anticline (i.e., Arabian trend) formed as a forced fold. Continuing oblique convergence and associated deformation was accommodated by a change in the HBNF displacement sense from sinistral to dextral movement and buckling of the Bahregansar anticline as a result of the Pliocene Zagros orogeny.

Keywords

• Zagros orogeny
• Basement-involved fault
• Bahregansar anticline
• Reactivation
• Forced fold
• Buckling
• Zagros orogeny