In the article from the Faculty of Geographical Sciences of the 91滴滴 and Dr Damian Moskalewicz from the University of Gdansk present the first such comprehensive study of sediments forming eskers formed on the soft-bed region during the Central Polish (Saalian) glaciation.
The research was conducted in seven eskers in central and northern Poland, where the eskers were preserved in the form of distinct, though often fragmentary, ridges. Detailed analyses of sediments exposed in gravel pits played a key role. Thirty sedimentological profiles, totalling nearly 190 meters in length, were examined, allowing for a very precise understanding of the internal structure of these formations.
Three Stages of Esker Formation Under the Ice Sheet
Analysis of the sediments made it possible to distinguish three main accumulation environments that together formed the eskers. The lowest sections of the ridges formed in deep, subglacial channels filled with water under high pressure. Coarse-grained sediments and boulders, very poorly sorted, often containing fragments of older sediments torn from the substrate by violent flows, dominated these areas.
The higher-lying sediments are associated with the formation of crevasses and fractures in the ice ceiling and the opening of tunnels. Water flow there was still very dynamic, but it now occurred at pressures close to atmospheric. This sub-environment is characterised by finer gravel and sand sediments with structures quite typical of braided rivers. Sediment deformations also occur, which are very sporadic in the lowest-facies sediments.
The highest parts of eskers formed in open water channels, where flow had varied, but generally significantly lower energy. The sediments of this sub-environment are dominated by sands, with gravel and silt also occurring. Deformation structures are common, including those indicating the loss of ice support and the collapse of sediments after the ice retreated.
Statistics in the Service of Geomorphology
In addition to classical sedimentological methods, the authors employed the Markov Chain Analysis, which statistically confirmed that the observed sediment sequences in the eskers were not random. The repetitive layering patterns reflect changing meltwater flow conditions and the gradual evolution of subglacial drainage systems.
Why is this research important?
Eskers are not only a striking feature of the postglacial landscape, but also a valuable archive of information about the operation of ancient ice sheets. Their structure allows us to reconstruct the course of subglacial tunnels, the rate of ice melt, and the dynamics of sediment transport.
The research allowed the development of a model of esker formation in the soft-bed region, showing how hydrological conditions under the ice sheet changed during its disappearance and how these changes were recorded in the structure of glaciofluvial forms.
The paper demonstrates that eskers formed on soft substrates differ significantly from classical models based on examples from rocky areas. This is an important step towards more realistic interpretations of glaciofluvial landforms that take into account local geology and the complexity of processes occurring beneath the ice sheet.
Frydrych Ma艂gorzata, Moskalewicz Damian: Eskers formed in the soft-bed region 鈥� a comprehensive study of Late Saalian strata from Poland, Sedimentology, 2025, DOI: 10.1111/sed.70046