MODERN HALITE DEPOSITION IN THE DEAD SEA AS AN ANALOG FOR PAST DEEP HYPERSALINE BASINS

Layered halite sequences were deposited in deep hypersaline basins throughout the geological record. However, analogues of such sequences are commonly studied in shallow environments. Here we study active precipitation of halite layers from the only modern analog for deep, halite-precipitating basin, the hypersaline Dead Sea. The link between spatiotemporal evolution of halite precipitation and the seasonal thermohaline stratification in the Dead Sea was characterized by means of monthly observations of the i) lake thermohaline stratification (temperature, salinity, density and degree of halite saturation), ii) textural evolution of the active halite deposits. We present the observed relationships between textural characteristics of layered halite deposits (i.e. grain size, consolidation, and roughness) and the degree of saturation, which in turn reflected the limnology and hydro-climatology. The lakefloor is divided into two principle environments: A deep hypolimnetic lakefloor in which halite continuously precipitates with seasonal variations, forming distinct summer and winter halite layers. A shallow epilimnetic lake floor is highly influenced by the seasonal temperature variations, and by intensive summer halite dissolution which results in thin sequences with annual unconformities. This emphasizes the control of temperature seasonality on the precipitated halite layers characteristics. In addition, precipitation of halite in the hypolimnetic floor, on the expense of the dissolution of the epilimnetic floor, results in lateral focusing and thickening of halite deposit in the deeper part of the basin and thinning of the deposits in shallow marginal basins. We termed this syndepositional thickening of depocentral halite - 'halite focusing'. Global distribution of halite units displays significant thickness variations over the basin and commonly show thick and massive halite in basins' depocenter vs. absence of halite in the basins' margins (e.g. MSC). These observations have been an enigma in evaporites study for decades and we suggest that depth dependence of halite deposition and the resulted 'halite focusing' to explain basinal halite distribution.