Lithospheric Structure of the Red Sea Based on 3D Density Modeling: A Contrasting Rift Architecture

The Red Sea is an ideal location for studying rifting processes, offering a young and active intra‐continental rift at the final stages of breakup. We explore the 3D lithospheric structure of the Red Sea by analyzing the gravity response of four end‐member models of rift architecture, including two end‐member types margin architecture Type I—narrow margins and exhumed lithospheric mantle, and Type II—(ultra)wide margins and removal of lithospheric mantle. Additionally, we test two options for the distribution of the oceanic crust (a) limited, that is, confined only to regions of magnetic stripes, and (b) extended, that is, available in vast areas within the basin. South of latitude 23°N, our results suggest the presence of ultrawide margins and limited oceanic crust. North of this latitude, the model of exhumed mantle and limited oceanic crust has minimized residuals compared to the observed gravity field, and agrees with a previously published regional tomographic model. Additionally, we find evidence for the presence of a high‐density body along the southern Arabian coast, probably associated with magmatic underplating. We discuss the lithospheric structure of the Red Sea with respect to the nearby Afar plume, agreeing that the close proximity of the central‐southern regions to the plume promoted a reduction in the strength of the lithosphere, and led to the development of ultrawide margins in these areas. Plain Language Summary The Red Sea is a young example of continental break‐up, a process in which a continent disintegrate into smaller pieces and an ocean is formed between them. We explore the sub‐surface structure of the Red Sea, down to 140 km, aiming to better understand the mechanisms that allowed the Arabian plate to separate from Africa ∼23 million years ago. We examine the gravity response of four end‐member models of rift structures and compare them to the gravity signal measured in this region. We find that the sub‐surface structure in the central‐southern region is different than in the northern regions. Toward the south, the crust is thin and stretched, the lithospheric mantle is absent, and the asthenosphere is rising in a wide region. In the north the lithospheric mantle is exhumed and the asthenosphere is rising in narrow regions below the center of the basin. We discuss the reasons for these differences and support the possibility that the Afar Plume, currently located to the south of the Red Sea, had a thermal weakening effect on the