EARLY DIAGENESIS OF HIGHLY SALINE LAKE SEDIMENTS AFTER EXPOSURE

Abstract

The present work describes processes that change, within decades, the composition of interstitial water and the mineral assemblage of the newly formed unsaturated zone in the coastal Dead Sea aquifer. The main processes are mixing between fresh groundwater and Dead Sea brine, and evaporation. The salinity of the interstitial solution gradually increases with decreasing distance to the sediment/atmosphere interface leading to the sequential precipitation of gypsum (CaSO4 . 2H2O), halite (NaCl), carnallite (KMgCl3 . 6H2O), and possibly sylvite (KCl) and bischofite (MgCl2 . 6H2O). The presence and depth of these salts in the profile was verified by SEM and also theoretically calculated using the PHRQPITZ code. In arid and hypersaline environments these processes can change syngenetic records and therefore could lead to the incorrect interpretation of the environmental conditions of deposition such as palaeosalinity and palaeoclimate.