Boron geochemistry reveals the evolution of Dead Sea brines

Hana Jurikova, Simon Ring, Michael Henehan, Ina Neugebauer, Birgit Schröder, Daniela Müller, Markus Schwab, Rik Tjallingii, Achim Brauer, Cécile Blanchet

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Abstract

Well-known for their geological and natural singularity, the Dead Sea brines evolved from a marine ingression of the Mediterranean during the Pliocene. Dead Sea brines are currently almost ten times more concentrated than seawater and have a unique chemical composition with high boron isotope values (Bbrine = ∼57‰). However, little is known on how these values were attained and their underlaying driving processes. Here we use boron isotopes (B) combined with B/Ca and B/Li of lacustrine authigenic aragonites from the deep basin drill-core ICDP 5017-1, and Ein Gedi and Masada profiles to reconstruct past brine conditions. Comparing reconstructed Bbrine from two key periods of contrasting hydro-climatic regimes we find that the brines of the late Holocene Dead Sea were enriched in 11B (Bbrine = ∼60‰) relative to its glacial precursor Lake Lisan (∼57‰). With the aid of boron cycle modelling, we quantify the main boron fluxes in the basin. We show that the post-glacial Bbrine enrichment is best explained by overall reduction of freshwater inflow to the lake and coeval increase in 10B sink through boron co-precipitation in evaporitic deposits and boron loss in atmospheric water vapour, consistent with the onset of warmer and drier climate in the Eastern Mediterranean during the Holocene. On geological time scales, adsorption of 10B on clastic sediments has acted as an important 10B sink and can explain the evolution of the high Bbrine values.
Original languageEnglish
Article number118403
Number of pages9
JournalEarth and Planetary Science Letters
Volume622
Early online date3 Oct 2023
DOIs
Publication statusPublished - 15 Nov 2023

Keywords

  • Boron cycle
  • Boron isotope
  • Seawater evolution
  • Plicoene Sedom Lagoon
  • Pleistocene Lake Lisan
  • Lacustrine authigenic aragonites

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