Models of post‐Miocene deformation of the Arabian Plate

We investigate the deformation of the Arabian plate along a profile which extends from the Red Sea in the southwest to the Zagros in the northeast. The post‐Miocene tectonic pattern of this region includes continuing uplift, volcanism, and extensional faulting at the western margin adjacent to the Red Sea; subsidence, folding, and thrusting at the eastern margin near the Zagros; and lack of major active tectonism in the interior. Thus, the near‐surface state of horizontal deviatoric stress changes from extensional to compressional over a broad region of small tectonic stress. We derive models that can explain the observed distributions of stress and vertical displacement. The stress distribution within the plate is derived from the static equilibrium of the lithostatic load, deviatoric tectonic stresses, and shear stresses along the base of the lithosphere. The vertical motions are derived from nonuniform vertical deviatoric stresses at the base of the lithosphere. The models indicate that the post‐Miocene deformation occurs by the combined effects of lateral density variations within the mantle part of the plate, ridge push at the Red Sea, and convective shear stress at the plate base. Density variations of 3.5% or less within the mantle part of the lithosphere induce a large portion of the tectonic stresses required for the observed deformation pattern in Arabia. The mean horizontal tensile tectonic stress in the lithosphere at the Red Sea cannot exceed 12.5 MPa for reasonable water depth in the Red Sea. The basal shear stress under Arabia must be directed toward the Zagros, and it ranges from 1 to 2 MPa. By modeling Arabia as a uniform viscous plate undergoing large‐scale bending, we find that the tectonic stresses generated by the lithospheric density variations and basal shear stress are sufficient to upwarp the Red Sea margins and downwarp the Zagros zone. A lithosphere viscosity of 5 × 10²⁴ Pa s gives uplift of the Red Sea region at a rate of about 0.1 mm/yr.