Holocene sedimentation in the central part of Lake Ladoga

Abstract

New multi-proxy paleolimnological study of the sediment sequence from the central part of Lake Ladoga enabled not only reconstructing the dynamics of the Holocene paleoenvironments, but also tracing changes in the lake ecosystem productive, sedimentation conditions and sedimentation rate. The analyses included lithology, loss-on-ignition, metals, grain-size distributions, including fractions of <1 μ, pollen and diatoms. A series of radiocarbon (AMS) data was also obtained. The earlier period (prior to 9000 cal. BP) is characterized with the lowest organic matter content and highest proportion of the fine sedimentary fraction (including that of <1 μ). The transition from periglacial to forest vegetation, climate warming, and the lake level drop are inferred. In the next period (9000-4700 cal. BP) warmest climate resulted in vegetation changes, increased productivity of the Lake Ladoga ecosystem as inferred from increasing siliceous microalgae concentration and organic matter content. In the late period (4700-1000 cal. BP) climate deterioration resulted in vegetation changes. However the lake ecosystem remained highly productive as inferred from high diatom concentrations.