Highly variable sediment deposition in Lake Imandra, NW Russia, since the Late Pleistocene

To understand the dynamics of sediment deposition and the potential influences of complex current systems in large lakes, Lake Imandra (Kola Peninsula) has been investigated. Seismic and echo-sounder data of the central part of Bolshaya Imandra reveal the sediment architecture in unprecedented detail. In addition, the sediment core data indicate highly variable depositional processes since the Late Pleistocene. The complex morphology of the lacustrine basin favoured accumulation of sediment in depressions, where they were preserved from erosion. Three main stratigraphic units (SU I-III) were identified above the acoustic basement. The oldest SU III is best preserved along a tectonic trench and interpreted as glacial deposits partly eroded by the Scandinavian Ice Sheet during Marine Isotope Stage (MIS) 2. The overlying SU II deposits are regarded as a till related to MIS 2 glaciation. The youngest SU I represents glaciofluvial, glaciolacustrine and lacustrine sediment deposited after ice retreat. As the north-south-trending main axis of Bolshaya Imandra runs parallel to the predominant wind direction, the basin is subject to strong wind-induced surficial currents and compensatory subsurface currents. These currents occur in water depth of 0-15 and deeper than 30 m, respectively, and their velocity prevents sediment accumulation.