A 2800-Year Multi-Proxy Sedimentary Record of Climate Change From Lake Cubuk (Goynuk, Bolu, Nw Anatolia)

Abstract

The sediment of Lake Cubuk in NW Anatolia, which is situated very close to the climate boundary between the dry Central Anatolia and the wet Marmara region, is regarded as a suitable climate archive to test inward and outward movements of this boundary in accordance with past climate variations. Herein, we study the stratigraphic record of the last 2800years of this landslide-dammed lake at 1030m elevation, using multi-proxy tools (sedimentology, major and trace element geochemistry, stable isotopes, pollen, diatoms and ostracods) and compare the results with other contemporaneous Anatolian climatic records. Our findings indicate that Lake Cubuk recorded seven distinct climatic periods in the last 2800years that have been previously revealed elsewhere in Anatolia. The most arid period occurred at the end of the Near-East Aridification Phase at approximately 200 BC when the O-18 shifted to very negative values, and the planktonic diatom ratio considerably decreased. The Dark Ages and the late Byzantine periods between AD 670 and 1070 are characterized by more positive O-18 values, increasingly higher lake levels and the most extensive arboreal cover of the entire record. The Little Ice Age' appeared suddenly, within 40years, at AD 1350 and is reflected in all of the proxies, including a positive shift in O-18, a sharp decrease in pollen of shrub and herb to the benefit of pine trees and a rapid increase in benthic diatom abundance indicating a lake level shallowing. In many parts of the record, a close match between the stable isotopes and the pollen assemblage zones in the last 2800years demonstrates that climate rather than human activity was the primary driver of vegetation cover in this mid-altitude mountain of NW Anatolia.