Geologic studies of present ocean basins and continental rift systems suggest a four-stage sedimentary model for evolution of rifted continental margins. Each stage produces a diagnostic sedimentary record, and examples of each can be seen today.( 1 ) Uplift, volcanism, rifting, and nonmarine sedimentation patterns characterize the rift valley stage. (2) In the Red Sea stage and later, restricted size and circulation of the proto-ocean create a reducing environment; chemical precipitates (halides, gypsum, and metallic sulfides) and saprophitic muds are deposited.(3) Gravity-induced processes dominate the sedimentary regime during the turbidite-fill stage, and flat-lying beds of coarse-grained, highly reflective sediments are formed. (4) Strong thermohaline contrasts in the mature ocean basin indicate geostrophic deep-water circulation. This deep-ocean current stage results in current-controlled sediment deposition and redistribution. 109 on July 29, 2015 memoirs.gsapubs.org Downloaded from 110