Evolution of the Eastern Red Sea Rifted margin: morphology, uplift processes and source-to-sink dynamics

This paper explores the formation and evolution of high-elevation passive margins, focusing on the morphology and uplift processes of the eastern Red Sea region and its relationship to the stratigraphy of the Red Sea (source-to-sink approach). We address gaps in our understanding of the origin and persistence of erosional escarpments along rifted margins and their connection to continental rifting. To achieve this, the research combines geological observations, geomorphic mapping and reconstructions of past topography to estimate erosion and compare it to accumulated sediment volumes in the basins. The study presents a landform map and an age model of landscape evolution of the Eastern Red Sea Rifted Margin (ERSRM), identifying 4 phases of erosion affecting two separate domains. On the Arabian plateau, remnants of the African surface (S-I) and an Oligocene planation surface (S-II) were rifted, uplifted and exhumed during rifting, and refreshed (S-III) since the onset of seafloor spreading. West of the escarpment, a young (< 15 Ma) foothill belt (S-IV) was carved by the eastward retreat of the Arabian Escarpment. We identified three different settings controlling the escarpment evolution and coastal plain morphology along the margin from north to south: (1) escarpment retreat from the rift fault towards the interior in the northernmost Red Sea, (2) escarpment retreat synchronously from two parallel rift faults and capture of a former endorheic drainage system, resulting in the formation of the biggest catchment in western Saudi Arabia (i.e., Wadi Hamd), and (3), escarpment retreat within a downwarped margin in the southern Red Sea, accompanied by sustained flexural uplift. These settings are the result of rift inherited structures segmenting the Red Sea, as well as the effect of the AFAR hotspot fading towards the north around the Jeddah latitude. Furthermore, we demonstrate that the escarpment evolution was not a steady process, as at the end of rifting similar to 16 million years ago, erosion rates were high and remain relatively high (although decreasing) up to 5 million years. Then a dramatic drop in erosion rates occurred, documenting the cessation of the escarpment retreat. We link this decrease in erosion and sedimentation rates to a global aridification of the climate throughout the Plio-Pleistocene. Finally, we discuss the complexity of escarpment evolution, both in terms of time and space, mitigating the often simplified vision of linear escarpment evolution. By bridging the gap between onshore geomorphic evolution and coastal basin stratigraphy, this study contributes to a comprehensive understanding of the long-term evolution of rifted margins.