Sedimentation and formation of secondary minerals in the hypersaline Discovery Basin, eastern Mediterranean

Two cores recovered from the Discovery Basin and one reference core from a location outside the Basin were investigated in detail in order to decipher the influence of hypersaline brines on sediment geochemistry. The cores contain a tephra layer (presumable Y-5) and carbonate microfossils which permit a tentative chrono- and lithostratigraphic correlation. A layer containing up to 60 wt% biogenic opal and 6.6 wt% organic carbon was identified in one basin core, which probably represents the best preserved example of eastern Mediterranean sapropel S-1. The basin is filled with a concentrated solution of MgCl2 which is enriched in dissolved sulfate and has the highest salinity ever encountered in the marine environment. Pore water profiles demonstrate that this brine dissolves sedimentary calcite to form secondary carbonate- and sulfate-bearing minerals. Of these, dolomite, magnesite and gypsum were identified by X-ray diffractometry; thermodynamic calculations show that these phases form in equilibrium with the anomalous brine composition.