Abstract
Sediment layers of uniform age within lakes (isochrones) and their patterns reflect accumulation processes which can be correlated with hydrologic conditions in lake basins. The sedimentary archives in three small dystrophic lakes in northeastern Poland are described based on the correlation of local pollen assemblage zones in cores that were collected from the centers and margins of each lake. Past regional groundwater levels could be discerned from the shape of the isochrones, whether plane parallel or concave in configuration in relation to the lake basin shape. The concave configuration of the isochrones in the studied lakes shows that regional groundwater levels remained mostly high and stable throughout their history. The water levels in each lake during the Late Glacial and throughout the Holocene were different and no single, common water-level fluctuation pattern was identified in the three water bodies. The lack of such a finding suggests that the lakes are influenced dominantly by local hydrological factors.
Highlights
The type and pattern of sediment accumulation in lakes are determined by many external and internal environmental factors (Bloesch 2004)
The sedimentary archives in three small dystrophic lakes in northeastern Poland are described based on the correlation of local pollen assemblage zones in cores that were collected from the centers and margins of each lake
If regional groundwater level is lower than the lake depressions and not directly connected to lake water level, lakes and ponds are formed only in these depressions where the bottom is sealed by clay and loam, precipitation and inflow from the catchment can collect
Summary
The type and pattern of sediment accumulation in lakes are determined by many external and internal environmental factors (Bloesch 2004). With regional groundwater levels connected to lake levels, the sediment layers accumulate over both the profundal and littoral zones (Gaudig et al 2006). If regional groundwater level is lower than the lake depressions and not directly connected to lake water level, lakes and ponds are formed only in these depressions where the bottom is sealed by clay and loam, precipitation and inflow from the catchment can collect. Some of these water bodies contain bottom sediments sealed off by humus colloids (self-sealing mechanism), which can include kettle holes
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