Lateglacial nunataks in central Scandinavia: Biostratigraphical evidence for ice thickness from Lake Flåfattjønn, Tynset, Norway

This study reveals for the first time biostratigraphical evidence of nunataks emerging from the Late Weichselian ice-sheet in central Scandinavia. Almost 1 m of minerogenic basal layers from Lake Flåfattjønn, 1110 m a.s.l., at Tynset, Norway, was deposited in the Lateglacial, possibly as early as 16,000 cal. yr BP. The sediments contain well-preserved remains of plants, diatoms and chironomids and indicate: (1) a mosaic pioneer vegetation of dwarf-shrub tundra, snow bed vegetation and xerophytes on wind-blown ridges, (2) an ice-free lake during summers with clear water at low pH due to little inwash, (3) a continental climate with summers slightly warmer than today (ca 10 °C), and most probably with very cold winters, according to indications of permafrost, and (4) a hiatus/reduced sedimentation during at least the first half of the Younger Dryas when the lake was sealed by a more-or-less permanent ice-cover. The existence of Lateglacial nunataks indicates a thin and multi-domed Lateglacial ice-sheet in Scandinavia. Early migration of arctic-alpine plants to nunataks could explain their centric distribution in S Norway. Furthermore, vegetation establishment on the Flåfatet Lateglacial nunatak indicates that S Norway could have been vegetated by successions along the retreating ice from alpine nunataks and from coastal and southern areas. The upland and lowland vegetation met at the final deglaciation.