Axial sedimentation of the Red Sea Transitional Region (22°–25° N): pelagic, gravity flow and sapropel deposition during the late Quaternary

Abstract

The Red Sea is an under-supplied marine rift basin. Study of sediments based on core and dredge samples from the Transitional Region (22°–25° N) show that offshore Quaternary sedimentation is predominantly pelagic-carbonate oozes with CaCO₃ contents up to 70 to 80%. Interruptions of this standard sedimentation style are due to climatically driven hydrological anomalies connected to sea-level lowstands (hard layers) and pluvial phases (sapropels). By using the last glacial/inter glacial cycle as a reference, it is apparent that the entire basin changes from organic to inorganic carbonate factories in tune with sea- level fluctuations, and that these events affect sedimentary processes and CO₂ sinks differently. While climate seems to be the leading factor in forcing sedimentation patterns in the offshore Red Sea, structure primarily controls the infilling of embryonic oceanic troughs (e.g. Nereus Deep) which, besides hydrothermal metal- enriched sediments, receives a significant input through mass gravity transport, mainly pelagic-calciturbidites. Various kinds of pelagic carbonates (ranging from hardgrounds to friable pteropod limestones) and mixed MORB volcanoclastic-carbonate rocks formed on sea- mounts and slopes of axial trough segments.