Deciphering the relationship between basement faulting and two-phase folding in the Hendijan anticline, northwest Persian Gulf, Iran

Abstract The Hendijan anticline in the northwestern part of the Persian Gulf, Iran, was analyzed using 2D/3D seismic and well data. Two folding phases of Late Cretaceous and Pliocene ages, associated with the 700 km long, NNE-SSW Hendijan-Bahregansar-Nowrooz strike-slip fault (HBNF), play an important role in the evolution of the anticline. The HBNF initiated as an oblique-normal basement fault during Late Proterozoic plate accretion on the Arabian margin of Gondwana, and in the Late Cretaceous due to regional compression and ophiolite obduction, it was reactivated as an oblique-reverse fault that formed a NNE-SSW forced fold in the cover. Based on seismic interpretation of key stratigraphic horizons, the analysis of sedimentary thicknesses, and restoration of a cross section across the anticline, the structural evolution of the Hendijan anticline comprises four stages: (1) Early to Middle Cretaceous which shows no evidence of folding, although the oblique normal slip of the HBNF controlled the deposition of sedimentary units in the NNE-SSW direction; (2) Late Albian to Middle Turonian which shows evidence of forced folding, growth strata, erosion, and the development of the Turonian unconformity; (3) Late Cretaceous to Middle Miocene which does not show significant thickness variations; and (4) Pliocene which shows growth strata and buckle folding related to the Zagros orogeny in response to compression associated with the collision of the Arabian and Eurasian plates. In this last stage, the Zagros orogeny overprinted the previously created NNE-SSW Arabian structures and reoriented them to their present NW-SE direction. The HBNF is still active as a blind fault and it has controlled the Miocene to present thickness variations although it tips out under the Lower Miocene Gachsaran evaporites.