Red sea evaporites: Formation, creep and dissolution

Evaporite deposition and seafloor spreading are two salient geological processes in the geological history of the Red Sea. We piece together the available evidence about rift evolution and evaporite formation to constrain the deposition history, analyze creep, and advance a plausible explanation for the preservation of these soluble formations. At the end of evaporite deposition before the Indian Ocean flooded the Red Sea through the Bab alMandab's strait, the salt thickness must have exceeded similar to 1.5 times the current thickness. Reported plate rotation, rift rates and the presence of a salt suture zone in the central Red Sea allow us to estimate an effective large-scale viscosity of 10(18) Pa.s. Thinned salt along the southern Red Sea flows up to 5 mm/yr, creep cannot keep up with seafloor spreading and oceanic crust remains exposed. Vast alluvial fans and carbonate platforms cause salt withdrawal; corresponding seafloor settlement rates can exceed similar to 10 mm/yr and overtake coral reef production. Salt dissolution leaves behind a residual sediment cap made of insoluble minerals that gradually retards further dissolution, i.e., self-armoring. New experimental evidence and the numerical solution of diffusion with a moving boundary show that self-armoring by selective dissolution controls early evaporite dissolution while background sedimentation dominates sediment accumulation over long time scales. Armoring-delayed evaporite dissolution prevents the formation of a vast regional brine pool.

Automated summary

Evaporite deposition and seafloor spreading are important geological processes in the history of the Red Sea. Studies suggest that before the Indian Ocean flooded the Red Sea, the thickness of salt deposits exceeded the current thickness. The rate of salt flow cannot keep up with seafloor spreading, resulting in exposed oceanic crust. Salt dissolution leaves behind a layer of insoluble minerals that retard further dissolution, preventing the formation of a large brine pool.