Formation of extensional strike-slip duplexes in transtensional settings: Evidence from the Fujairah Basin, Gulf of Oman

The Fujairah Basin, offshore northeastern United Arab Emirates, occupies a tectonically complex position along the northeastern Arabian Plate, close to the transition between the Zagros collision, the Minab–Zendan strike-slip system, and the Makran subduction zone. Although previous studies recognized late basin extension, the timing, geometry, and kinematics of shallow post–Middle Miocene faulting and its relation to present-day seismicity remained poorly constrained. This study integrates 2D seismic lines, 3D seismic cube, three exploration wells, and a high-resolution multibeam bathymetry data to characterize shallow fault architecture, link seafloor ruptures to subsurface structures, and reconstruct the late post-collisional evolution of the basin. The results reveal eight extensional strike-slip duplexes (S1–S8) arranged along NNW–SSE trending sinistral master faults, with lengths increasing northeastward from ~5–20 km to ~50 km. In seismic sections, these structures form negative flower geometries, whereas in map view they define rhombic to irregular fault-bounded domains with extensional horses oriented at ~15–50° to the master faults. Horizontal slices from the 3D seismic data support a sinistral interpretation of the fault system, the map-view arrangement of overlapping master strands, extensional imbricate fans, and associated graben–half-graben arrays. Many shallow subsurface faults extend to the seafloor, where they form curvilinear escarpments, horsts, and grabens that coincide with clusters of shallow microseismicity (<5 km depth), indicating ongoing tectonic activity. Seismic evidence indicates Late Miocene initiation of duplex formation on pre-existing structural highs, followed by Pliocene to Early Quaternary along-strike propagation, overlap, and multiphase reactivation, and culminating in Late Quaternary composite duplexes coeval with eastward tilting and southeastward progradation. These observations indicate that the Fujairah Basin records a post–Middle Miocene transition from compression to transtension, driven by intraplate sinistral shear and extension along the northeastern Arabian margin. The study refines the basin-scale tectonic framework and demonstrates that shallow active deformation in the Fujairah Basin is structurally linked to extensional strike-slip duplex development in a transtensional setting.