Boron isotope systematics of lacustrine carbonates: a new approach for tracing the palaeo-hydroclimatic evolution of the Dead Sea

Sedimentary sequences of the Dead Sea provide a unique high-resolution archive of past climatic changes in the Mediterranean-Levant, a key region for human migration out of Africa at the boundary of hemispheric climate belts. The well-preserved record of the Holocene Dead Sea and its Last Glacial precursor Lake Lisan is characterised by annual laminations - varves - composed of alternate layers of aragonite and detritus. Past lake level reconstructions suggest large fluctuations in the regional hydrological balance driven by abrupt climatic events, including a pronounced transition from lake level high-stand during the Last Glacial Maximum (LGM) to a low-stand at the onset of the Holocene [1]. On millennial timescales these changes have been associated with temperature variations recorded in the Greenland ice core, underscoring the potential of the Dead Sea to offer both regional and global perspectives on high-amplitude climatic events in the past. However, our ability to fully read the Dead Sea record critically depends on reliable extraction of palaeo-climatic and palaeo-environmental data from lacustrine carbonates, and an improved understanding of their formation. Here we present carbon, oxygen, boron isotope and trace element composition of hand-picked authigenic aragonite from a Dead Sea deep-drilling core (ICDP 5017-1; [2]) and shore outcrops. While traditionally used as a pH-proxy [3], we examine the possibility of applying boron geochemistry for reconstructing the source water and brine composition [4]. Using our innovative combined approach, we elucidate the palaeo-hydroclimatic evolution of the Dead Sea during intervals of major environmental changes since the end of the LGM. [1] Torfstein A., et al. (2013) Quat. Sci. Rev. 69, 1-7. [2] Neugebauer I., et al. (2014) Quat. Sci. Rev. 102, 149-165. [3] Jurikova H., et al. (2019) Geochim. Cosmochim. Acta 248, 370-386. [4] Vengosh A., et al. (1991) Geochim. Cosmochim. Acta 55, 1689-1695.