Onshore-offshore evidence for active tectonics and the propagation of the Zagros deformation front into the Persian Gulf

The Zagros Mountains in southwest Iran are a young orogen displaying the geodynamic evolution in an active continental collision zone. We combine the analysis of geomorphology, remote sensing, geochronology, and seismic-reflection data to investigate the current kinematics of the Zagros foreland in SW Iran and identify tectonically active structures associated with the propagation of the deformation front of the Zagros fold-and-thrust belt. Seismic-reflection data in the Persian Gulf show evidence of syndepositional folding since at least >300 ka BP. These data define the propagating deformation front of the Zagros fold-and-thrust belt by outlining actively growing, modern folds in the Persian Gulf several tens of kilometers off the coast. RTK GNSS surveying and geochronological dating were used to estimate the uplift rate of terraces on the southwestern limb of an onshore anticline. The uplift of such terraces and the development of new folds in the Persian Gulf indicate that shortening in the Zagros is accommodated within a wide zone (∼40–50 km) rather than along a linear deformation front. Congruent dextral bending of the northern hinges of fold axes, both on- and offshore, is interpreted to be linked to ongoing shortening accompanied by slip partitioning along the N-trending basement faults. This study demonstrates the benefit of analyzing contemporaneous incipient deformation and syn-kinematic sedimentation to outline a progressive deformation front in an active fold-and-thrust belt.