LAUSR

Abstract Two and a half meters of sediments from Lake Heimtjonna in the Scandes Mountains reveal changes in the vegetation, climate, and sediment environment since deglaciation. The lake was deglaciated in the Late-Glacial (LG), perhaps as early as 16-18 ka cal BP. After deglaciation, the sediment environment at the Heimtjonna coring point was extraordinary and challenging to interpret. The genesis of the 1.7 m basal unsorted sediments including large stones is discussed concluding that the layer was rafted by lake-ice after the LG deglaciation. The Younger Dryas (YD) established a semi-perennial lake-ice that stopped the deposition of the ice-rafted stone-rich sediments. In the early Holocene, the unstratified and well-sorted clayey silt shows fluvial origin. In late Holocene, strong flood activity including the major flood disaster ‘Stor-Ofsen’ in AD 1789, caused a sediment hiatus at the coring point from ca 9.5 ka cal BP to ca 250 a cal BP. The LG interstadial warming initiated the succession from pioneer plants on mineral soils towards local dwarf-shrub heath. July temperatures reached at least 7–8 OC. In the LG and early Holocene, Papaver radicatum, Artemisia norvegica, and Campanula cf. uniflora today occurring at Dovre and with centric Scandinavian distributions, locally established. All have previously been connected to Weichselian survival on nunatak refugia. Continuous pollen curves of spruce (Picea abies) support the much-debated LG and early Holocene presence of spruce in the Scandes mountains. For the first time, it is shown that both grey alder (Alnus incana) and Armeria occurred in the Scandes in the LG and early Holocene. Due to dating errors, LG ages is exclusively based on stratigraphical correlations and considerations. The LG chronology must be thoroughly tested by future studies providing reliable AMS 14C-dates of terrestrial fossils.