A discussion on the structure and evolution of the Red Sea and the nature of the Red Sea, Gulf of Aden and Ethiopia rift junction - Continuous seismic reflexion profiles in the Red Sea

Abstract

Twenty continuous seismic reflexion profiles have been made across the main trough of the Red Sea north of 17 degrees N latitude. The main trough is characterized by mildly deformed sediment layers along the margins with highly disturbed materials in the deeper axial trough. A strong seismic reflector is observed at depths up to 500 m beneath the main trough, but is not found in the axial trough. This reflector may represent an unconformity of late Miocene-Early Pliocene age (5 to 6 Ma ago). On the assumption that this unconformity was once continuous across the main trough but has subsequently rifted apart as a result of seafloor spreading in the axial trough, separation distances of 48 to 74 km across the trough imply a minimum seafloor spreading rate of 0.4 to 0.7 cm a$^{-1}$. This rate is lower than spreading rates inferred from magnetic anomaly profiles in the Red Sea; however, if separation began as late as 2 to 3 Ma ago which can be inferred from the seismic profiles, a rate of 1.4 to 0.9 cm a$^{-1}$ is indicated. This rate is in good agreement with those determined from magnetic profiles.