Sedimentary lipid biomarkers in the magnesium rich and highly alkaline Lake Salda (south-western Anatolia)

Lake Salda located in south-western Anatolia is characterized by the presence of living stromatolites and by a low diversity of both phytoplankton and zooplankton due to high pH and magnesium concentration. The most abundant, free sedimentary lipids of the uppermost centimetres of the lake sediments were studied as potential environmental biomarkers, and proxies based on glycerol dialkyl glycerol tetraethers (GDGT) were tested in this extreme environment. Dinosterol and tetrahymanol are potentially relevant biomarkers for the dinoflagellate Peridinium cinctum and ciliates, respectively. C20:1 and C25:2 highly branched isoprenoid (HBI) alkenes, and n-C17 alkane and n-C17:1 alkene are considered as representing, respectively, diatoms and Cyanobacteria involved in the formation of the stromatolites. Isoprenoid GDGT-0 is assumed to be derived mainly from Euryarchaeota (methanogens), and crenarchaeol from Thaumarchaeota. Allochthonous organic material is represented by long-chain n-alkanes and n-alkanols derived from land plant leaf waxes, as well as branched GDGTs produced by soil bacteria. While pH and temperature proxies based on branched GDGTs are likely not applicable in Lake Salda, TEX86 (tetraether index of tetraethers consisting of 86 carbons), a proxy based on isoprenoid GDGTs, potentially allows estimating mean annual lake surface temperature. Interestingly, C23 and C25 1,2 diols, which have a yet unknown origin, were found for the first time in lake sediments. This study represents the first investigation of sedimentary lipid distribution in an alkaline and magnesium-rich lake in Anatolia, and provides a basis for future biomarker-based paleoenvironmental reconstruction of Lake Salda

sj-pdf-1-hol-10.1177_09596836231163508 – Supplemental material for A novel Bayesian multilevel regression approach to the reconstruction of an eastern Mediterranean temperature record for the last 10,000 years

Supplemental material, sj-pdf-1-hol-10.1177_09596836231163508 for A novel Bayesian multilevel regression approach to the reconstruction of an eastern Mediterranean temperature record for the last 10,000 years by Z Bora Ön, Neil Macdonald, Sena Akçer-Ön and Alan M Greaves in The Holocene</p

Geochemical proxies of sediment core Hz11-PO3 from Lake Hazar in Eastern Anatolia

The elemental composition of lake sediment cores is often the result of several independent processes. In this study we attempt to extract statistically independent climate related signals from µ-XRF multi element data of a core drilled from Lake Hazar in Eastern Anatolia, using the independent component analysis (ICA) method. In addition, we analysed ostracod shells for oxygen and carbon isotopes. The ICA method has advantages over traditional dimension reduction methods, such as principal component analysis or factor analysis, because it is based on maximal statistical independence rather than uncorrelatedness, where independence is a stronger property. The Hz11-P03 core, which represents the last 17.3 ka, was recovered from Lake Hazar which, at times, formed the headwaters of the Tigris. Applying the ICA method, we selected two out of six independent components by measuring distance correlation similarity. We propose that one of the selected components can be read as a proxy for temperature and the other for precipitation in this region. Our results indicate that the region was relatively cold and wet during the late glacial, between 17.3 and 14.8 ka BP, and wet and warm during Bølling-Allerød. The lake level dropped below today's level during the Younger Dryas stadial (12.49 and 11.76 ka BP), forming a marked hiatus in the core's stratigraphic record. During the beginning of the Holocene, while precipitation values were high, the temperature gradually increased until 8 ka BP. Between 8 and 5 ka BP, the region was warm but extremely dry. After 5 ka BP, around 3.5 ka BP temperatures suddenly fell, and three abrupt dry phases are observed around 3.5 ka and 2.8 ka and 1.8 ka BP