Abstract
Glacial landscapes of the Land of Great Masurian Lakes and Suwałki Lakelands in northeast Poland are characterized by very high abundance of lakes. These two areas were surveyed for lakes containing laminated sediments. Using bathymetry as a criterion, 60 small, deep lakes, representing preferred conditions for formation and preservation of lacustrine non-glacial varves, were selected for gravity coring. We found laminated sediments in 24 of the lakes, 15 in the Land of Great Masurian Lakes and 9 in the Suwałki Lakeland. Seven of these 24 sediment records were laminated in the topmost part only. Analysis of lake morphometric variables showed that the relation between surface area and maximum water depth can be used to identify lakes with laminated sediments. Most of the newly discovered lakes with laminated deposits have surface areas ≤0.3 km2 and maximum depths of 15–35 m. Multivariate statistical analysis (Linear Discriminant Analysis) of the lake dataset identified the morphological features of lake basins and their catchments that largely control preservation of laminated sediments. Microscopic and geochemical analyses revealed a biogenic (carbonaceous) type of lamination typical for lakes in northeast Poland. Such lakes are characterized by a spring-summer lamina that is rich in calcium carbonate and an autumn-winter lamina composed of organic and minerogenic detritus. This pattern may be modified by multiple periods of calcite deposition during a single year or substantial contribution of clastic material. Laminations and high sedimentation rates offer the possibility of high-resolution investigation of past climate and environmental changes through application of myriad biological, isotopic and geochemical proxies.
Highlights
High-resolution investigations of climate change and human impact on ecosystems are currently among the most common studies in environmental research
Glacial landscapes of the Land of Great Masurian Lakes and Suwałki Lakelands in northeast Poland are characterized by very high abundance of lakes
To test the above assumptions we conducted investigations in two areas, the Land of Great Masurian Lakes (GML) and the Suwałki Lakeland (SL) (Fig. 2), which are characterized by the highest number of lakes in the region
Summary
High-resolution investigations of climate change and human impact on ecosystems are currently among the most common studies in environmental research. With the increasing number of investigations of lacustrine sediment profiles, it is evident that these are key archives that provide reliable information about past climate and environmental changes (Ojala and Alenius 2005; Tomkins et al 2008; Corella et al 2011) Invaluable in this respect are annually laminated (varved) sediments, which are a source of proxy data for tracking ecosystem response to climate change (Randsalu Wendrup et al 2012) or for quantitative palaeoclimatic reconstruction (Larocque-Tobler et al 2010), but enable precise dating at annual resolution (Zolitschka 2007). These changes, including human influence, can interrupt laminated sequences or initiate the formation of laminated sediments
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