Hydrological and thermodynamic controls on late Holocene gypsum formation by mixing saline groundwater and Dead Sea brine

Nurit Weber, Gilad Antler, Boaz Lazar, Mordechai Stein, Yoseph Yechieli, Ittai Gavrieli

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

The rapid retreat of the Dead Sea during the past four decades led to the exposure of unique structures of massive gypsum along the shores. Many of these structures (having the shape of mounds) are associated with the activity of Ein Qedem-type saline springs that currently discharge Ca-chloride brine to the lake. Field observations, radiocarbon dating of aragonite (within the gypsum mounds) that yield ancient ages, and the narrow range of δ34S and δ18O values (δ34Sgyp: 14.1–16.9‰; δ18Ogyp: 14.4–16.5‰) indicates that the formation of the gypsum structures is related to the mixing of brines: the Dead Sea brine and ancient (last glacial) Ein Qedem type brine. These are Ca-chloride brines having different salinities and sulfur concentrations that satisfy conditions of an outsalting process whereby supersaturation of gypsum is attained by the mixing of these two brines in the offshore shallow water environment. Thermodynamic calculations (using the PHREEQC software) show that gypsum outsalting occurred when both brines were enriched with sulfate as compared to the present. The Ein-Qedem brine had higher sulfate when subjected to less intensive bacterial sulfate reduction. The Dead Sea was characterized by higher sulfate concentrations during intervals of low lake stands. The conditions of higher sulfate concentrations and enhanced discharge of the saline springs occurred repeatedly in the Dead Sea between ∼6.6 to 0.6 ka and were intermittent with periods of enhanced supply of sulfate to the lake by freshwaters.

Original languageEnglish
Pages (from-to)363-383
Number of pages21
JournalGeochimica et Cosmochimica Acta
Volume316
DOIs
StatePublished - 1 Jan 2022

Keywords

  • Brines
  • Dead Sea
  • Hydroclimate
  • Lacustrine Gypsum
  • Outsalting
  • Saline springs
  • Thermodynamic modeling

ASJC Scopus subject areas

  • Geochemistry and Petrology

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