Chronology, lithology, palynology and biogeochemistry of sediment cores from East Greenland lakes

Sediment cores from two lakes in the outer coastal region of East Greenland were investigated for chronology, lithology, palynology, and biogeochemistry. A 10 m long sequence recovered in Basaltsø comprises the entire lake history following the last glaciation of the area, probably during the Preboreal oscillation. This is indicated by a succession from glacial via glaciolimnic to limnic sediments. Deglaciation of the area was associated with a high sedimentation rate, mirrored also in the basal part of a 2.6 m long core from a smaller lake (B1) about 1 km south of Basaltsø. Limnic sedimentation without glacial influence commenced about 10 000 cal. yr BP according to radiocarbon-dated terrestrial plant remains. Biogeochemical and palynological data indicate an early Holocene climatic optimum from 9000 to 6500 cal. yr BP A climatic deterioration began at 6500 cal. yr BP with an increase in snow accumulation, documented by a change in the pollen assemblage and a coinciding change in the grain-size distribution. At least since 5000 cal. yr BP, a decrease in the biogeochemical parameters in both lake sediment successions indicates a temperature decline. This deterioration culminated at about 3000-1000 cal. yr BP, when the climate was cold and dry. A slight warming is indicated in the pollen assemblage between ca. 1000 and 800 cal. yr BP. Following a subsequent rise in precipitation, cooling during the Little Ice Age is mirrored in lowest dwarf shrub pollen percentages and in low contents of organic components.