Akademik Veri Yönetim Sistemi
QUATERNARY SCIENCE REVIEWS, cilt.104, ss.8-17, 2014 (SCI-Expanded)
Lake Van sediment cores from the Ahlat Ridge and Northern Basin drill sites of the ICDP project PALEOVAN contain a wealth of information about past environmental processes. The sedimentary sequence was dated using climatostratigraphic alignment, varve chronology, tephrostratigraphy, argon argon single-crystal dating, radiocarbon dating, magnetostratigraphy, and cosmogenic nuclides. Based on the lithostratigraphic framework, the different age constraints are compiled and a robust and precise chronology of the 600,000 year-old Lake Van record is constructed. Proxy records of total organic carbon content and sediment color, together with the calcium/potassium-ratios and arboreal pollen percentages of the 166-m-long event-corrected Ahlat Ridge record, mimic the Greenland isotope stratotype (NGRIP). Therefore, the proxy records are systematically aligned to the onsets of interstadials reflected in the NGRIP and synthesized Greenland ice-core stratigraphy. The chronology is constructed using 49 age control points derived from visual synchronization with the Greenland ice-core stratigraphy using the GICC05 timescale, an absolutely-dated speleothem timescale (e.g., Hulu, Sanbao, Linzhu cave) and the Epica Dome C timescale. In addition, the uppermost part of the sequence is complemented with four ages from Holocene varve chronology and three calibrated radiocarbon ages. Furthermore, nine argon argon ages and a comparison of the relative paleointensity record of the magnetic field with reference curve PISO-1500 confirm the accuracy of the age model. Also the identification of the Laschamp event via measurements of Be-10 in the sediment confirms the presented age model. The chronology of the Ahlat Ridge record is transferred to the 79-m-long event-corrected composite record from the Northern Basin and supplemented by additional radiocarbon dating on organic marco-remains. The basal age of the Northern Basin record is estimated at similar to 90 ka. The variations of the time series of total organic carbon content, the Ca/K ratio, and the arboreal pollen percentages illustrate that the presented chronology links ice-marine-terrestrial stratigraphies and that the paleoclimate data are suited for reconstructions and modeling of the Quaternary and Pleistocene climate evolution in the Near East at millennial timescales. Furthermore, the chronology of the last 250 ka can be used to test other dating techniques. (C) 2014 Elsevier Ltd. All rights reserved.