The deep accumulation of ¹⁰Be at Utsira, southwestern Norway: Implications for cosmogenic nuclide exposure dating in peripheral ice sheet landscapes

Cosmogenic nuclide exposure dating is a widely used method for constraining past ice sheet histories. We scrutinize a recently published data set of cosmogenic ¹⁰Be data from erratic boulders in Norway used to constrain the deglaciation of the western Scandinavian Ice Sheet to 20 ka. Our model of the ¹⁰Be inventory in glacial surfaces leads us to conclude that the chronology may be afflicted by the deep subsurface accumulation of ¹⁰Be during long-lasting ice-free periods that resulted in ¹⁰Be ages >10% too old. We suggest that the majority of the dated erratic boulders contain a uniform level of inherited muon-produced ¹⁰Be and were derived from bedrock depths >2.5 m and most likely ~4 m. The implication of our finding is that for landscapes that experience long ice-free periods between brief maximum glacial phases, glacial erosion of >5 m is required to remove detectable traces of inherited ¹⁰Be.