Climate implications and lithological characteristics of sediments from Lake Van (Turkey) and Lake Ohrid (Macedonia / Albania) obtained from downhole logging data

Abstract

In this thesis, downhole logging data from Lake Van (Turkey) and Lake Ohrid (Macedonia/Albania) was analyzed to improve paleoenvironmental studies. The sediments of Lake Van (clayey silts and tephra) were differentiated by downhole logging and XRF scanning data. Spectral gamma ray (SGR), zirconium intensities and magnetic susceptibility are most useful to separate the lake facies from tephra. The U data from SGR was used for cyclostratigraphic studies to estimate the duration of deposition. The sediments were deposited over a period of 587 ka and the results agree with core interpretations. High-frequency cycles were correlated with interstadials from the North Greenland Delta-18-O record (NGRIP) for the past 75 ka. Gamma ray (GR) and potassium (K) fluctuations obtained in the sediments of Lake Ohrid correlate with variations in Delta-18-O values from the global benthic isotope stack LR04. In combination with eight tephrostratigraphical tie points, a robust age model over the past 630 ka was established.