Stable oxygen and carbon isotopes in Late Glacial–Holocene freshwater carbonates from Belarus and their palaeoclimatic implications

摘要

Four sets of δ~(18)O and δ~(13)C curves were derived from Late Glacial to mid-Holocene spring and lacustrine carbonates from Belarus. Stratigraphic division was carried out by palynological studies and δ~(14)C-dating. It was revealed that variations of isotopic compositions and the dynamics of terrestrial vegetation were affected to some extent by common climatic forcing: birch expanded during relatively warm and/or arid phases (higher δ~(18)O and/or δ~(13)C), fir spread during relatively cold and/or humid phases (lower δ~(18)O and/or δ~(13)C), and grasses were abundant during relatively cold (lower δ~(18)O) or arid phases (higher δ~(13)C). A comparison of four pairs of δ~(18)O and δ~(13)C curves allowed the recognition of several palaeoclimatic events at a regional scale. Two main cold events interrupted by a warmer interval occurred in the Younger Dryas. A short-term episode of active permafrost decay at the end of the Younger Dryas and in the very beginning of the Preboreal caused an abrupt rise of lake levels followed by their rapid fall. A shift toward a lower precipitation–evaporation balance and lower lake levels took place roughly in the middle of the Boreal. A trend of decreasing temperatures throughout most of the Boreal culminated in a short-lived very cold phase at ～8100 14C year BP or ～9050 cal. δ~(14)C year BP, according to the proposed age model. In the Atlantic 1 warmer phases were coincident with the phases of the lower precipitation–evaporation balance. An episode of significant short-term warming occurred in the last third of the Atlantic 1. Correlation of the 18O curve derived from authigenic calcites precipitated between the beginning of the Preboreal 2 and the end of Atlantic 1 in the Ptich river valley with that from the GISP2 Greenland ice core allowed good matching of the trends and spikes (i.e. of the air temperature changes) under assumption that the ages of the Ptich pollen-based time model are 600–1000 years too old.