Late Holocene Climate Change in Central Finland (62º-64Nº) Recorded by the Annually Laminated Lake Sediments

The deepest basins of six small lakes (Lake Kalliojarvi, Lake Kortejarvi, Lake Korttajarvi, Lake Kallio- Kourujarvi, Lake Lehmilampi and Lake Vahajarvi) depositing varved sediment in Central and Eastern Finland have been cored through winter ice using piston corers and wedge-shaped freeze coring techniques to obtain continuous sediment sequences extending until the present year. The lakes investigated have almost similar surface area with water depth varying between 10.5 and 12.5 m. So far 2-5 m (covering last 2000- 6000 yrs) of finely laminated sediment from all lakes has been impregnated in low viscosity epoxy resin using the water-acetone-epoxy-exchange technique. Laminae counts and thickness measurements have been made using thin sections or image analysis techniques from scanned X-ray radiographs depending on the varve type. Micro XRF technique was applied to study geochemical variations in high resolution. Our preliminary results (Haltia-Hovi et al. 2007) suggest that Finnish annually laminated sediments are excellent material for studying the past climate change and the impact of solar forcing on sedimentation. Due to their precise time control varved sediments can be correlated with other high resolution climate proxies.