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Paleogeographic reconstructions of the Northwest Karelia region evolution in the holocene based on the study of small lake sediments

2020; Karelian Research Centre of RAS; Issue: 9 Linguagem: Inglês

10.17076/lim1268

2312-4504

Татьяна Станиславовна Шелехова, Nadezhda Lavrova, Т. S. Shelekhova, Nadezhda Lavrova,

Geological formations and processes

The results of a study of bottom sediments from two small nameless lakes located on the proximal side of Salpausselkä II (Kalevala) glacial deposits at various elevations within glacial-lacustrine and morainic plains are reported. Using a set of methods, including spore-pollen, diatom and radiocarbon (C14) analyses, new data were obtained on the onset of the formation of the lakes, stages of their development, sedimentation of organic sediments and the effect of local geomorphological conditions on the composition of spore-pollen spectra and diatom complexes in different paleoclimatic periods in the Holocene. Evidence shows that the lakes began to form virtually simultaneously with glacial retreat. Terrigenous sediments accumulated in the lakes in Preboreal time. They were replaced by organic sediments about 9140 ± 220 (C14) B. P., i. e. 200–450 years later than in the eastern and southeastern parts of Kalevala marginal deposits. A hiatus was revealed in the deposition of bottom sediments in one of the lakes lying at a higher absolute elevation. The hiatus was due to a drop in the water level in Boreal time caused by a change to a more xeric climate and a glacioisostatic uplift of the crystalline Fennoscandian Shield. Vegetation dynamics from Preboreal time to the present day was reconstructed.