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    Build-up and chronology of blue ice moraines in Queen Maud Land, Antarctica
    (Elsevier, 2020) Akcar, Naki; Yesilyurt, Serdar; Hippe, Kristina; Christl, Marcus; Vockenhuber, Christof; Yavuz, Vural; Ozsoy, Burcu
    Blue ice moraines are common supraglacial landforms in Antarctica and they are considered to record the ice volume fluctuations. In this study, we use photogrammetry and the analysis of multiple cosmogenic nuclides (Be-10, Al-26, and in-situ C-14) in boulders on three blue ice moraines to explore the timing of ice volume fluctuations in the Sor Rondane Mountains, Queen Maud Land, and provide insights into the role of sediment sources in the reconstruction of their chronology. In the field, we observe that the blue ice moraines are composed of subglacially and supraglacially transported sediments. Cosmogenic Be-10 and Al-26 exposure ages of 14 surface samples, collected from boulders on three blue ice moraines, range from 15.4 +/- 1.1 to 659.5 +/- 33.9 ka. Al-26/Be-10 ratios vary between 3.53 +/- 0.20 and 7.01 +/- 0.32, and many of these ratios indicate complex exposure histories. In contrast, among nine in-situ C-14 exposure ages, five vary between 4.2 +/- 0.1 and 22.0 +/- 1.3 ka, and four are saturated. We conclude that the accumulation of these blue ice moraines commenced before or during the global Last Glacial Maximum. Our results indicate that surficial sediment sources can yield exposure ages that are older than real exposure age, and exhibit a wider scatter. This can alter the reconstructed chronology of these landforms. The analysis of in-situ C-14 has a high potential in tracking the pace of their evolution, especially since the Last Glacial Maximum.
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    LGM Glaciations in the Northeastern Anatolian Mountains: new insights
    (MDPI-Multidisciplinary Digital Publishing Institute, 2022) Reber, Regina; Akçar, Naki; Tikhomirov, Dmitry; Yeşilyurt, Serdar; Vockenhuber, Christof; Yavuz, Enver Vural; Ivy-Ochs, Susan; Schluechter, Christian
    Barhal Valley belongs to the Coruh Valley System in the Kackar Mountains of northeastern Anatolia. This 13 km long valley is located to the south of the main weather divide and to the east of Mt. Kackar, with the highest peak of the mountain range being 3932 m. Today, source of an average yearly precipitation of 2000 mm of moisture is the Black Sea, situated approximately 40 km to the north of the study site. Glaciers of the Last Glacial Maximum (LGM) descended directly from Mt. Kackar and reached an altitude of ca. 1850 m a.s.l. (above sea level). In this study, we are exploring whether the position of Barhal Valley to the south of the main weather divide and its east-west orientation have an influence on the existence and expansion of paleoglaciers. Here, we present 32 new cosmogenic Cl-36 dates on erratic boulders from the Coruh Valley System. We reconstructed three geomorphologically well-contained glacier advances in the Barhal Valley, namely at 34.0 +/- 2.3 ka, 22.2 +/- 2.6 ka, and 18.3 +/- 1.7 ka within the time window of the global LGM. Field evidence shows that the glacier of the 18.3 +/- 1.7 ka advance disappeared rapidly and that by the latest time, at 15.6 +/- 1.8 ka, the upper cirques were ice-free. No evidence for Lateglacial glacier fluctuations was found, and the Neoglacial activity is restricted to the cirques with rock glaciers. A range of 2700 to 3000 m for the Equilibrium Line Altitude (ELA) at the LGM was reported based on modeling of the glacial morphology. We determined that the most likely position of the LGM ELA in the coruh Valley System was at 2900 m a.s.l. We suggest an alternative moisture source to the direct transport from the Black Sea for the ice accumulation in the Eastern Black See Mountains. The shift of the Polar Front and of the Siberian High Pressure System to the south during the LGM resulted in the domination of easterly airflow to the Caucasus and Kackar Mountains with moisture from expanded lakes in central-western Siberia and from the enlarged Aral- and Caspian Seas.