Landscape preservation under fennoscandian ice sheets determined from in situ produced 10Be and 26Al

Derek Fabel*, Arjen P. Stroeven, Jon Harbor, Johan Kleman, David Elmore, David Fink

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    227 Citations (Scopus)

    Abstract

    Some areas within ice sheet boundaries retain pre-existing landforms and thus either remained as ice free islands (nunataks) during glaciation, or were preserved under ice. Differentiating between these alternatives has significant implications for paleoenvironment, ice sheet surface elevation, and ice volume reconstructions. In the northern Swedish mountains, in situ cosmogenic 10Be and 26Al concentrations from glacial erratics on relict surfaces as well as glacially eroded bedrock adjacent to these surfaces, provide consistent last deglaciation exposure ages (~8-13 kyr), confirming ice sheet overriding as opposed to ice free conditions. However, these ages contrast with exposure ages of 34-61 kyr on bedrock surfaces in these same relict areas, demonstrating that relict areas were preserved with little erosion through multiple glacial cycles. Based on the difference in radioactive decay between 26Al and 10Be, the measured nuclide concentration in one of these bedrock surfaces suggests that it remained largely unmodified for a minimum period of 845+461-418 kyr. These results indicate that relict areas need to be accounted for as frozen bed patches in basal boundary conditions for ice sheet models, and in landscape development models. Subglacial preservation also implies that source areas for glacial sediments in ocean cores are considerably smaller than the total area covered by ice sheets. These relict areas also have significance as potential long-term subglacial biologic refugia.

    Original languageEnglish
    Pages (from-to)397-406
    Number of pages10
    JournalEarth and Planetary Science Letters
    Volume201
    Issue number2
    DOIs
    Publication statusPublished - 2002

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