Cosmogenic 10Be dating of ice sheet marginal belts in Mecklenburg-Vorpommern, Western Pomerania (northeast Germany)

Abstract

Northeastern Germany was repeatedly covered by the Scandinavian Ice Sheet during the last glaciation and a succession of distinct ice marginal belts is present in Mecklenburg-Vorpommern. We used surface exposure dating to develop a time frame for the retreat of the ice margin. Two samples from the Saalian ice marginal belt give Weichselian ages, a problem that has also been encountered further south when attempting to date the same ice marginal belt (the Hoher Fläming) in Brandenburg. One sample from the Frankfurt moraine is too young to be associated with this glacial feature. Another single sample from the Velgast extent gives also an exposure age that is too young to be associated with this glacial feature. These two examples highlight the necessity to sample multiple boulders on the same feature to obtain a reliable exposure age. Fourteen samples were collected on the Pomeranian moraine and 12 were used to calculate an average deposition time of 15.6 ± 0.6 10Be kyr. Two samples were removed from the age distribution based on statistical grounds. This result is in good agreement with results obtained in Brandenburg where the Pomeranian moraine was dated at 16.4 ± 0.7 10Be kyr. Five samples from the Mecklenburgian moraine give an average age of 13.7 ± 0.6 10Be kyr in good chronological order with the Pomeranian moraine age. One sample (MVP-21) from the Mecklenburgian moraine was corrected for burial effect based on historical documents demonstrating that if known, the recent past history of exposure of a surface can be appropriately used to calculate an exposure age. Together, this new data set highlights: 1. the difficulty to date surfaces older than the Weichselian glaciation when using only one cosmogenic radionuclide, 2. the consistency of the results obtained for the Pomeranian moraine across northeastern Germany using cosmogenic Be-10.