Paleoenvironmental and paleoclimatic variations around Lake Van (Eastern Turkey) recorded by sedimentary source specific biomarkers 250-130 ka (MIS7 and MIS6)

Paleoclimatic changes during MIS7 and MIS6 remain poorly described in the Near East. We quantified source-specific biomarkers in Lake Van sediments during the interglacial/glacial cycle MIS7/MIS6. Long-chain n-alkanes produced by land-derived vegetation, as well as long-chain alkenones and sterols (namely brassicasterol and dinosterol) produced by aquatic algae were investigated. Stable hydrogen isotopic measurements (delta H-2) on n-C-29 alkanes were used as a proxy for aridity and revealed three wetter periods interrupted by two drier intervals during MIS7. In contrast, during the MIS6 glaciation, a generally drier climate was predominant. During the warmer and wetter periods of MIS7, a higher input of aquatic organic matter to Lake Van sediments was recorded by higher concentrations of long-chain alkenones, dinosterol and brassicasterol. Long-chain alkane abundances do not show a pattern related to aridity and were observed in higher concentrations in wetter as well as drier periods. Generally, in the Eastern Mediterranean, a wetter interglacial interrupted by drier episodes followed by a dry glacial period was the common feature observed during the MIS7/MIS6 interglacial/glacial cycle. However, in comparison to the last interglacial/glacial cycle the extreme dry glacial period registered around Lake Van from MIS5d to MIS2 was apparently unique and not equaled by a similar event within the last 250 ka. (C) 2019 Elsevier Ltd. All rights reserved.