Be-10 age of the Local Last Glacial Maximum in the southern of the Scandinavian Ice Sheet

• Main Authors: Tylmann, Karol, Rinterknecht, V., Woźniak, Piotr
• Other Authors: Faculty of Oceanography and Geography, University of Gdansk
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDE]Environmental Sciences; Ice Sheet
• Online Access: https://hal.archives-ouvertes.fr/hal-03546878

International audience The Last Glacial Maximum (LGM) is defined as the most recent period with the maximumglobal integrated volume of ice-sheets and the corresponding minimum global sea level. It is usually dated at 23-19 cal. ka BP or 24-18 cal. ka BP and centred at 21 cal. ka BP. However, most of the ice sheets reached their maximum expansion in a 7500 year time interval between 26.5 ka and 19.0 ka, and the maximum extents of specific ice sheets were found to be asynchronous and not always in agreements with the global LGM. Therefore, the term Local Last Glacial Maximum (LLGM) is used to define the timing of the regional maximum expansion of a particular ice sheet.Here we present a set of 10Be exposure ages of erratic boulders located in the vicinity of the last Scandinavian Ice Sheet (SIS) maximum limit in Poland. The largest erratic boulders located in-situ on glacial landformswere our target for sampling. Samples were taken with a manual jackhammer from the upper surface of stable, massive boulders of quartz-rich lithologies and were subjected to the standard laboratory procedure of quartz purification and 10Be measurements used in terrestrial cosmogenic nuclide exposure dating.Our results consist of exposure ages for seven boulders located in front of the last SISmaximum extent and for 13 erratics located within the extent of the last SIS, close to itsmaximum limit. Moreover, we recalculated already existing 10Be ages for seven bouldersaccording to the most recent production rate. The exposure ages of pre-LLGM erratics show significant scatter, ranging from 7.1 ± 1.0 to 122.2 ± 14.2 ka. For LLGM erratics, 10Be ages range between 6.1 ± 1.0 and 72.2 ± 7.8 ka. The distribution of the LLGM population is multimodal with modes occurring at ca. 6-7 ka, 18-19 ka and 42-46 ka. The dataset reveals three significantly different distributions: the youngest including two ages of 6.1 ± 1.0 ka and 7.4 ± 1.0 ka, an intermediate distribution consisting of ages ranging between 13.8 ± 1.8 and 26.0 ± 2.8 ka, and the oldest ...