Geology Club Seminar
Arms 151 (Buwalda Room)
Extreme aridity cycles in the Middle East during the last interglacial revealed by halite deposition in the Dead Sea
Yael Kiro,
Lamont Doherty Earth Observatory,
The Middle East experienced unstable climate during the last interglacial, varying from wetter intervals to extreme aridity. The ICDP Dead Sea Deep Drill core reveals thick intervals of halite that precipitated during the interglacials, representing the driest conditions in the Dead Sea watershed, which stretches from the Saharan–Arabian desert belt to the Mediterranean climate zone. The halite layers alternate with mud, representing cycles of hundreds of years in which the climate varied between relatively wet (similar to present day precipitation) and arid climate (below 50% of present precipitation). Based on the chemical compositions of fluid inclusions in the halite (Na/Cl~0.3-0.6), we estimate that ~14-16 cm of halite precipitates per 1 m of lake level drop. Although halite represents extreme aridities, the presence of gypsum and detritus between the halite layers and crystals shows that even during arid intervals there was water input into the lake. The halite alternates between small cumulate crystals that are formed on the water surface and large bottom-growth crystals that are formed on the lake floor. The large crystals are associated with mud layers, while the cumulate crystals have much less detritus and contain 'halite rafts', which are formed under high evaporation conditions. The frequency of these alternations ranges from thick layers of only 'bottom-growth halite' to rapid seasonal alternations between the two crystal types. These different facies of halite represent the order of aridity and maybe even the seasonality of precipitation. While proxies and climate models show high precipitation and relatively wet conditions in the Middle East during the peak of the last interglacial, the peak margins were clearly extremely dry. The diversion from the Mediterranean climate (wet winters and dry summers) is also indicated by climate models showing a continuous decrease in winter precipitation during the last interglacial, explaining the continuous negative water budget
For more information, please contact Lisa Christiansen by phone at 626-395-6127 or by email at [email protected].
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