Dunai, Tibor

We provide a geomorphological analysis of a glacial valley on Mount Pelister, in Macedonia. Three boulders from a frontal moraine were dated with the cosmogenic nuclide isotope 10Be. The results demonstrate that the boulders have been exposed since 15.24 ± 0.85 ka. This age constrains the formation of the frontal moraine to the Oldest Dryas cold event. This age fits with that of other glacier deposits dated to the Older Dryas in the Alps, Balkans, Carpathians and Turkish mountains. The Pelister palaeoglacier has been reconstructed and its equilibrium line altitude extracted, returning a value of 2250 ma.s.l. This is in good agreement with the equilibrium line altitudes of most other reconstructed glaciers of the same age in the circum- Mediterranean mountains, demonstrating a comparable response to the Oldest Dryas event. Other palaeoenvironmental records near the Pelister mountain indicate that the Older Dryas was here characterized by a cold and remarkably dry event. The temporal relationship between Older Dryas glacier advances in the Balkan region and recorded changes in the Atlantic thermohaline circulation during the Laurentide Ice Sheet massive ice discharge (H1 event) confirms the strong climatic link between the pan-Mediterranean regions and the North Atlantic Ocean.

This study presents the first cosmogenic 36Cl surface exposure data from a moraine in the Former Yugoslav Republic of Macedonia (FYROM). Five limestone boulders from an end moraine in the Galicica Mountains (40.94°N, 20.83°E, 2050 m a.s.l.) were used for cosmogenic 36Cl surface exposure dating. The 36Cl concentrations from the five boulders are identical within their measurement uncertainties ruling out major effects of inheritance, erosion, or snow cover. The calculated ages are very consistent ranging from 11.3 ± 1.3 to 12.8 ± 1.4 ka (mean 12 ± 0.6 ka) after applying a Ca-spallation production rate of 56 at g−1 a−1 (LSD scaling) and correction for 5 mm ka−1 carbonate weathering and 2% snow shielding. The applied corrections for weathering and snow shielding cause a shift to older ages in the order of magnitude of ca. 5% on average, making the production rate the main impact on exposure ages. The ages point to a moraine formation during the Younger Dryas period, consistent with the timing of the last deglaciation in the Galicica Mountains derived from previous geomorphological studies in the area. The formation of a glacier was likely favoured by several topoclimatic factors, accounting for additional snow input. This interpretation is in line with regional studies on glaciation chronologies from Šara Range (FYROM/Republic of Kosovo), Retezat Mountains (Romania), Mt. Chelmos (Greece), Mount Orjen (Montenegro) and Durmitor (Montenegro). Lake sediment analyses of Prespa (Republic of Albania/FYROM/Greece), Maliq (Republic of Albania) and Dojran lakes (FYROM/Greece) indicate that cold conditions promoted the formation of a local cirque glacier. However, studies of sediment records of the adjacent lakes Ohrid (Republic of Albania/FYROM) and Prespa do not indicate the presence of a proximal glaciation. An explanation might be a combination of the small size of the cirque glacier, generating only small amounts of debris, and the karstic bedrock, which hampers fluvial transport and acts by its aquifer system as a natural sediment trap, as the fluvial transport of the sediments to the lakes is absorbed by the karst system.