Rifting in the Red Sea – insights into the rift architecture from geophysical data

Conjugate margins along mature oceans indicate two end-member types of rifted margins, distinguished by their crustal architecture, e.g. the Iberia-Newfoundland and Central South Atlantic. Numerical simulations and analogue models show that these types could be explained by rheology, state of stress (depth depended) and role of magmatism (magma assisted). The Red Sea is a young rift, offering the opportunity to study early break-up conditions and to relate them to the architecture and the type of passive margins. The morphology of the Red Sea indicates variability and dissimilarities between its southern and northern regions, nevertheless, the lithospheric structure of the rift remains elusive, mainly due to lack of high-resolution direct geophysical measurements, e.g. seismic profiles.

In this study, we explore the deep architecture of the Red Sea rift using geophysical data, in particular gravity and magnetic data, and constraints from seismic interpretations, receiver functions and tomographic models. We present a 3D structural and density model for the Red Sea, including the African and Arabian shoulders down to 120 km depth. The model includes four main sections: sediments, crystalline crust (continental and oceanic), lithospheric mantle (including a thermal gradient) and a uniform asthenosphere. In order to test different scenarios, we evaluate combinations of (1) exhumed continental mantle lithosphere (Type I margin) versus wide/ultrawide continental crust (Type II margin), and, (2) limited versus extended distribution of oceanic crust. The 3D gravity model favors Type II architecture and limited oceanic crust in the southern-central parts of the Red Sea rift. In the northern parts, the model cannot distinguish between the pre and post break-up stages.