Tectonic inversion in the Bandar Jissah Area: evidence for Cenozoic contraction in northern Oman

The geology of northern Oman and eastern Arabia is distinctive because of the emplacement of the Semail Ophiolite onto the stable Arabia platform in the late Cretaceous followed by the later development of the Jebal Akhdar and Saih Haitat domes. East of Muscat, the Wadi Kabir Fault forms an important structure along which the northern edge of the Saih Hatat domes was unroofed.  In the Bandar Jissah area, Triassic carbonates occur in the footwall of the NNE-dipping Wadi Kabir Fault while rocks of the Semail Ophiolite, newly discovered rocks of the metamorphic sole, and a sequence of Paleogene sedimentary rocks crop out in the footwall.  Some workers posit that the Wadi Kabir and associated faults form basin-bounding faults for the Bandar Jissah rift basin and that folds in the hanging wall cover sequence are the product of rollover during basin formation.

However, our detailed mapping and kinematic analysis illustrates that folds in the hanging wall are actually contractional structures that formed due to tectonic inversion along the Wadi Kabir and other faults.  The overall shortening is modest (~10%) and primarily confined to the hanging wall rocks, consistent with buttressing against mechanically rigid rocks in the footwall of the Wadi Kabir Fault.  These structures require an interval of N-S directed shortening in northern Oman  that post-dates the deposition of mid-Eocene marine sediments in the Seeb Formation. The Wadi Kabir Fault also has localized zones of listwaenite preserved in its damage zone derived from ophiolitic rocks. Collectively, the Wadi Kabir Fault is a long-lived structure that’s experience multiple episodes of extensional and contractional slip since the Paleocene.