Holocene sediment record from Briaunis palaeolake, Eastern Lithuania: history of sedimentary environment and vegetation dynamics

This paper presents new data describing the Holocene environmental history of the Briaunis pal­ aeolake, Eastern Lithuania. Shortly before 9600 cal yr BP, sedimentation began in an oligotrophic deep­water basin, whereas the Early Holocene instability of the environmental regime caused the influx of detrital sediment into the basin. A birch forest dominated in the surrounding landscapes, and at ca. 9600 cal yr BP, the spread of Ulmus, Alnus, Populus and Corylus began, suggesting a short­lived climatic amelioration. A subsequent drop of the water table and increasing influx of the terrigenous material continued from 9600 to 9300–9200 cal yr BP. The ensuing climatic stability caused the formation of a deciduous forest and the regional spread of Picea. Some instability, i.e. a decline in the thermophilous species, as well as the appearance of boreal and northern alpine diatoms, could be associated with the so­called “8.2 ka event”. This reversal was followed by ameliora­ tion and prospering of the water plants typical of the Holocene climatic optimum from 7900 to 7200–7100 cal yr BP. At aproximatelly 6600–6500 cal yr BP, a small rise of the water table was documented and bog­forming processes dominated until ca. 3600–3400 cal yr BP, when a small­scale deepening of the basin occured.