Biomarkers in Lake Van sediments reveal dry conditions in eastern Anatolia during 110.000-10.000 years B.P.

Lipid biomarkers were analyzed in Lake Van sediments covering the last 600 ka, with a focus on the period between 110 and 10 ka, when a broad maximum in pore water salinity as a relict from the past suggests dry conditions. The occurrence and distribution of biomarkers indicative for terrestrial plants (long-chain n-alkane C₂₉), haptophyte algae (methyl alkenones C₃₇) and halophilic archaea (archaeol) all point toward a dry climate in Lake Van region during this time interval. The hydrogen isotopic composition of C₂₉ n-alkanes (δD_C29) and C₃₇ alkenones (δD_C37) is enriched between MIS 4 and MIS 2, which is interpreted as a decrease in the regional ratio of precipitation to evaporation. Similarly, the low abundance of the acyclic glycerol dialkyl glycerol tetraether GDGT-0 relative to archaeol, quantified by the Archaeol and Caldarchaeol Ecometric (ACE) is assumed to reflect the presence of halophilic euryarchaeota adapted to high salinity water. The climate around Lake Van appears in phase with the Yammouneh basin 800 km southwest and Lake Urmia 250 km southeast of Lake Van over the last two glacial periods. The results highlight the potential of combining ACE, δD_C29, and δD_C37 for reconstructing salinity changes and regional precipitation to evaporation ratio from lake sediments.