Millennial-scale fluctuations of palaeo-ice margin at the southern fringe of the last Fennoscandian Ice Sheet

Abstract. The paper presents a study of reconstructing chronology and dynamics of palaeo-ice margin oscillations at the southern fringe of the last Fennoscandian Ice Sheet (FIS) based on combined luminescence and ¹⁰Be surface exposure dating. The study area is located in northern Poland close to the last FIS maximum limit. Luminescence method was used to date sandy deposits (fluvioglacial sediments and aeolian deposits filling fossil periglacial wedges) intercalating basal till layers, and the most likely age of the tills was constrained by Bayesian modelling. ¹⁰Be dating method was used on erratic boulders left during the final retreat of the last FIS and resting on at the surface of glacial landforms. Our results indicate millennial-scale oscillations of the last FIS in northern Poland between ~19 and ~17 ka. The last FIS retreated and re-advanced over a relatively short period of time (2–3 ka), leaving a lithostratigraphic record (basal tills) of three ice re-advances in a millennial cycle: 19.2 ± 1.1 ka, 17.8 ± 0.5 ka and 16.9 ± 0.5 ka. The paper presents the first terrestrial record of millennial-scale palaeo-ice margin oscillations at the southern fringe of the FIS during the last glacial cycle. We explore the dynamics of these oscillations and confront the proposed cycles of the southern FIS advances and retreats with existing patterns of the last deglaciation and millennial-scale fluctuations of the last FIS inferred from marine records.