Lithospheric evolution of eastern Arabia based on surface wave and receiver function analyses

The geodynamic evolution of Eastern Arabia comprises three major events that must have acted on the entire lithosphere below the present-day passive continental margin. Starting with the Pan-African plate assembly during the Late Proterozoic, NNE-oriented structural trends were established which were reactivated during Infracambrian and Ordovician extension. Permian Pangean breakup and rifting created two rift axes to form the present-day geometry of the eastern and northern passive margins of Eastern Arabia. SW-directed obduction of the Semail Ophiolite during the Late Cretaceous was the latest major tectonic event that shapes the present-day geology of northern Oman. Recent anisotropic ambient noise tomography, surface wave analysis of earthquake data and receiver function analysis reveal the present-day lithospheric thickness of similar to 100 km, and the previously unknown, highly variable internal structure of the East Arabian continental crust. We integrate all newly available seismological observations into a consistent geodynamic model that describes the evolution of lithospheric thickness and crustal heterogeneity, identifies crustal segmentation and relates inherited structures to lateral variations within the dynamics of ophiolite obduction. A sharp, NNE-striking contrast of similar to 10% in shear wave velocity (V S) in the lower crust separates felsic Arabian continental crust in the NW from intermediate lithologies in the NE of Oman. This crustal segmentation is interpreted as being established during the Pan-African orogeny. High V S in the lower crust of northeastern Oman is likely due to Permian mafic intrusions related to the Pangean breakup. Mild crustal thickening below todays high topography is attributed to Late Cretaceous time, where northward continental subduction below the Neo-Tethys led to underthrusting and thickening of the continental crust and ultimately to obduction of the Semail Ophiolite. After post-obduction relaxation, we argue that lithospheric thickness, margin perpendicular fast directions of anisotropy and contemporaneous mid- to late Eocene basanite intrusions are indicative of an overall relaxed state of stress of the lithosphere at that time. In consequence, we propose marginal erosion of the base lithosphere on the passive Arabian plate margin during the Late Eocene as a geodynamic process that facilitated margin-wide emergence of the Oman Mountains. Altogether, the present configuration of the lithosphere in northeastern Arabia preserves imprints from Late Proterozoic Pan-African assemblage, Permian Pangean break-up, Late Cretaceous subduction and ophiolite obduction, and Cenozoic postobduction evolution.

Automated summary

The geodynamic evolution of Eastern Arabia consists of three main events: Pan-African plate assembly, Infracambrian and Ordovician extension, and Permian Pangean breakup and rifting. The obduction of the Semail Ophiolite during the Late Cretaceous and the subsequent relaxation of the lithosphere are also significant. Seismological observations reveal the lithospheric thickness and crustal heterogeneity of Eastern Arabia, indicating the segmentation of the crust and the impact of various tectonic events. The configuration of the lithosphere in northeastern Arabia preserves imprints from multiple geological periods.