Lake sedimentation conditions in the lower part Seyda River (north of Komi Republic, Russia) according to palynological and diatom data

Abstract

The aim of the study is to investigate sedimentation processes during the Late Glacial and Holocene in the eastern Bolshezemelskaya Tundra. The coastal outcrop SD-5, 16 m high, in the lower reaches of the Seyda River (Komi Republic) was studied. Analytical methods included palynological and diatom analysis, and ¹⁴C dating. When characterizing the stages of sediment formation, algae Pediastrum, Desmidiales, and other non-pollen palynomorphs were also identified. The lithological structure of the outcrop and the results obtained made it possible to trace the transformations of the periglacial paleo-reservoir and the four main stages of sedimentation associated with them. The banded clay at its base was deposited in a periglacial lake under periglacial conditions. The overlying layer of interbedded sands accumulated as a result of the descent of the periglacial paleo-reservoir. The peat exposed in the roof of the section was initially formed (12125±49 – 8719±44 ¹⁴C BP) in a cold deep-water lake that arose in place of a periglacial reservoir. The vegetation cover consisted of yernik and wormwood-chenopodium thickets. Later (up to ~ 4500 ¹⁴C BP) the shallows were overgrown with wetland plants. The improvement of the climate contributed to the advance of birch and later (7705±43 ¹⁴C BP) spruce forests. Then, starting from ~ 4500 ¹⁴C BP, the swamp massif drained and froze, and modern plant communities developed.