Patterns and chronology of the Lateglacial environmental development at Pamerkiai and Kašučiai, Lithuania

This paper focuses on the characteristics and chronology of Lateglacial environmental changes in Lithuania, in the context of the North Atlantic climatic events of the Last Termination. The reconstruction of environmental changes and their magnitude is based on new multiproxy data (lithology, pollen, plant macrofossils, diatoms and 14C dating) obtained from two sediment sequences from southeastern (Pamerkiai outcrop) and western (Kašučiai Lake) Lithuania. The spread of sparse open-ground vegetation with the patchy occurrence of Betula nana and Betula sect. Albae on the nutrient-poor unstable soils surrounding the oxygen-rich, alkaline water basins has been recorded pre-14,300 cal BP (correlated to the GI-1e event). The increased abundance of cold-tolerant plants (Artemisia, Chenopodiaceae and Armeria sp.) indicates a short climatic deterioration from about 14,300 to 14,100 cal BP, tentatively correlated with the GI-1d event. The palaeobotanical record indicates a continuing climatic amelioration and forestation of the region with open Betula-Pinus forest during 13,700–12,600 cal BP (approximately correlated to the GI-1c-a event). However, from 13,300 cal BP the spread of Artemisia, Chenopodiaceae and Thalictrum implies some instability in environmental conditions. Climate cooling resulted in a significant reduction in tree cover contemporaneous with the formation of an open, herb–grass dominated landscape, and low water levels in the nutrient-limited water basins during the period 12,600–11,100 cal BP. This has been tentatively correlated to the GS-1. However, the gradual expansion of Pinus after 11,500 cal BP suggests some amelioration of the climate, which might have been more apparent in the coastal region of Lithuania than in the rest of the country. Finally, after 11,100 cal BP, and contemporaneous with these improved climatic conditions, there was a rapid expansion of Betula and eutrophication of the water basins. These registered environmental shifts coincide with those of the North Atlantic region, which have been determined as climatically driven, and indicate the broad areal extent of these changes during the Lateglacial period.