Abstract
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 (10Be, 26Al, and in-situ 14C) in boulders on three blue ice moraines to explore the timing of ice volume fluctuations in the Sør 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 10Be and 26Al 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. 26Al/10Be 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 14C 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 14C has a high potential in tracking the pace of their evolution, especially since the Last Glacial Maximum.
Highlights
Supraglacial sediment accumulations from the subsurface and/or locally from slope processes and meteorite falls in blue ice areas of Antarctica are attributed to blue ice moraines
We use photogrammetry and the analysis of multiple cosmogenic nuclides (10Be, 26Al, and in-situ 14C) in boulders on three blue ice moraines to explore the timing of ice volume fluctuations in the Sør Rondane Mountains, Queen Maud Land, and provide insights into the role of sediment sources in the reconstruction of their chronology
To investigate the competence of in-situ cosmogenic nuclides in calibrating the timing of events in the formation of blue ice moraines and explore the potential effects of the sediment source on the reconstruction of their chronology, we focus on the blue ice moraines in the vicinity of the Princess Elisabeth Station in the Sør Rondane Mountains in Queen Maud Land in Antarctica (Fig. 1)
Summary
Supraglacial sediment accumulations from the subsurface and/or locally from slope processes and meteorite falls in blue ice areas of Antarctica are attributed to blue ice moraines. Blue ice moraines are generally thought to be composed of subglacial sediments transported to the surface by the sublimation of ice (Corti et al, 2008; Sinisalo and Moore, 2010). Those linked to a nunatak, can contain additional supraglacial sediments deriving from the nunatak itself, such as slope debris captured gradually by the ice and/or a direct deposition on the ice by rock fall or avalanches
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