Magnetic Properties of Late Holocene Dead Sea Sediments as a Monitor of Regional Hydroclimate

Abstract

Microbial sulfate reduction (MSR) occurs commonly in reducing redox environment (Canfield & Berner, 1987; Morse & Cornwell, 1987; Wilkin & Barnes, 1997) where it can affect significantly the magnetic properties of sediments by causing titanomagnetite dissolution and by triggering authigenic greigite (Fe 3 S 4) precipitation (

Decadal Geomagnetic Secular Variations From Greigite Bearing Dead Sea Sediments

“…Thermal demagnetization curves from Ein‐Feshkha and Ein‐Gedi (Figure 4f2 and 4i2 respectively) are in agreement with the conclusions of Ebert et al. (2020), showing low blocking temperature of ∼350°C for the greigite‐bearing sediments of Ein‐Feshkha and higher blocking temperature range, from ∼350°C to 550°C, for the titanomagnetite‐bearing sediments in Ein‐Gedi. Acquisition of a gyroremanent magnetization (GRM) during AF demagnetization (e.g., Sagnotti & Winkler, 1999; Snowball, 1997) was observed only in few samples (Figures 4b, 4e, and 4h).…”

“…Ebert et al. (2020) suggested that the high values of magnetic parameters at Og and Ein‐Feshkha sections (170–320 cm) correspond to high content of the mineral greigite; intermediate values of magnetic parameters, at Ein‐Gedi section (0–120 and 200–260 cm) and at Ein‐Feshkha section (0–170 and 320–460 cm), indicate lower content of greigite; and low magnetic parameters values at Ein‐Gedi section (130–200 cm) are associated with dominance of the mineral titanomagnetite. The ratios and the MDF shown in Figure 3 are in agreement with these conclusions.…”

“…The declinations of the two sections overlap, but the inclinations show some dissimilarities: the fast change in the inclination of the Ein‐Feshkha sediments between 2,500 and 2,400 cal yr BP is not observed in the Ein‐Gedi section and the inclinations of the Ein‐Gedi sediments are much shallower than those of Ein‐Feshkha after 2,000 cal yr BP. The inclination difference in the lower part of Ein‐Gedi section can be explained by the geochemical pore‐fluids measurements that showed a clear influence of Ein‐Qedem spring brine (Ebert et al., 2020), which might have caused a secondary magnetization. The lower inclination of the upper part of Ein‐Gedi section suggests that this section, which is poor in greigite, is more affected by inclination shallowing and smoothing.…”

“…The Holocene Ze'elim formation comprises sequences of silty detrital sediments, the ld facies (laminated detritus) (Haliva-Cohen et al, 2012) consisting of quartz and calcite as major minerals interbedded with sequences of aragonite and detritus laminae the aad facies (alternating aragonite and detritus) (Machlus et al, 2000). The Dead Sea sediments contain two dominant magnetic minerals: titanomagnetite and greigite (Ebert et al, 2018(Ebert et al, , 2020Frank et al, 2007aFrank et al, , 2007bRon et al, 2006). Titanomagnetite is transported to the lake by fluvial and alluvial systems, carrying a detrital remanent magnetization (DRM).…”

“…)), indicating that greigite precipitation stops due to lack of labile organic matter (Ebert et al, 2020). The sulfate reduction rate (SRR) calculated by Häusler et al (2014) for the modern Dead Sea in the top 12 cm of the sediment, indicates that sulfate reduction in the late Holocene environment of the shallow Dead Sea margin may be reduced to a minimum depth of a few dozens of centimeters below the lake's surface sediment.…”