Trona in Nile Cone Late Quaternary sediments: Probable redepositional origin

Abstract

Trona and thenardite, evaporites formed in arid terrestrial settings, are identified in Late Quaternary sediments cored on the outer Egyptian Shelf and the Rosetta Fan of the Nile Cone, eastern Mediterranean. The distinct spatial—temporal distribution of these minerals suggests emplacement by resedimentation rather than an authigenic or artifact origin. Trona probably was eroded from saline deposits on the subaerially exposed continental margin during the last major eustatic low stand when the Nile Delta migrated northward toward the outer shelf (from about 23,000 to 18,000 years B.P.); evaporites then were transported downslope and rapidly buried with fine-grained terrigenous sediment in deep marine environments. Trona in some younger sections (at about 5000 and 2500–3000 years B.P.) may record Late Holocene changes in climate or of paleoceanography, but more likely can be attributed to slumping and downslope displacement of some outershelf evaporite-bearing sections.