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| Titel |
Long-term freshening of the Dead Sea brine during the last glacial revealed by porewater Cl- and δ¹⁸O in ICDP Dead Sea deep-drill |
| VerfasserIn |
Boaz Lazar, Orit Sivan, Yosseph Yechieli, Elan Levi, Gilad Antler, Ittai Gavrieli, Mordechai Stein |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250099486
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| Publikation (Nr.) |
 EGU/EGU2014-15271.pdf |
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| Zusammenfassung |
| The geological evolution of the unique Dead Sea Ca-chloride brine has been the focus of
many research efforts for several decades. These studies relied on the information obtained
from sedimentary exposures of the marginal terraces of the modern Dead Sea, mostly
documenting the history of the surface lake brine during its high stands periods. The present
study is the first attempt to establish the history of the deepest part of the lake by direct
measurements of the chemical and isotopic composition of pore-fluids that were
extracted from cores drilled during 2011 by ICDP in the deep basin of the Dead Sea at
water depth of 300 m. The vertical profiles of chloride (Cl-) and oxygen isotopes
(δ18O) in pore brines reveal a substantial decrease in the salinity of the hyper-saline
lake during the last glacial and particularly during MIS2 (~31-17 ka BP). The Cl-
concentration of the deep brine in the lake decreased gradually reaching a minimum of
less than 2/3 of its present value while the δ18O on the same time increased to
maximum of ~7o(3ohigher than today). The low Cl- indicates significant
dilution of the bottom water mass (hypolimnion) of Lake Lisan (the last glacial
predecessor of the modern Dead Sea) during its highest stand period. Beforehand,
during the interglacial and later during the post-glacial and the Holocene the Cl-
concentrations and δ18O values were similar to those of the modern Dead Sea. The
slow dilution of the deep Ca-chloride brine was caused probably by continuous
turbulent mixing of the hypolimnion with the less saline high δ18O epilimnetic brine,
across the epilimnion/hypolimnion interface (EHI). While the increase in δ18O
during the salinity decrease of Lake Lisan is a result of “normal” evaporation of the
less saline epilimnetic brine, the post-glacial δ18O decrease (contemporaneous
with salinity increase) is attributed to the “backward” behavior of δ18O during
evaporation of high salinity brine. During the long freshening period the hypolimnion was
enriched with dissolved sulfate supplied by the freshwater and transported by the
turbulent mixing across the EHI until reaching gypsum saturation that commenced
massive gypsum deposition at the end of this period, when full overturn took place. |
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