Halite focusing and amplification of salt layer thickness: From the Dead Sea to deep hypersaline basins

Worldwide stratigraphic records present thick halite layers accreted in deep hypersaline basins under dry climate conditions. The thickness and distribution of these halite units are used in basin analyses and paleoenvironmental reconstructions. Recent studies have raised doubts regarding the assumption that a given halite layer's thickness is directly related to net evaporation of the overlying water, where the areas of both water surface and deposited halite are similar. Here we present halite focusing, a limno-sedimentological model for halite accumulation based on observations from the Dead Sea. The model accounts for a halite-saturated hypersaline basin under negative water balance and a stratified water column. Under such stratification, double-diffusive flux transfers dissolved salt from the epilimnion (upper water layer in a stratified lake) down to the hypolimnion, resulting in an undersaturated epilimnion and continuous halite focusing; i.e., large amplification (increasing thickness of halite layers) of its accretion in the depocenter, at the expense of dissolution from the shallow basin margins. Halite focusing can almost triple the thickness calculated by uniform precipitation, meaning that a given halite unit may have accumulated faster, during shorter, less-arid intervals than previously proposed. Halite focusing explains (1) extremely high deposition rates, (2) accretion of exceptionally thick halite sequences in deep basins, and (3) a marginal basin that is fully or partially devoid of halite, with coeval thick sequence deposition in the deep basin.