Anthropogenic transformations in the glaciotectionical area in the Polish part of the Muskau Arch

The eastern part of the transboundary UNESCO Global Geopark Muskau Arch and the southern part of the Landscape park of the same name include four areas that are the subject of research in a project financed by the OPUS National Science Centre (No. 2019/33/B/ST10/02975).

The Muskau Arch is a unique moraine structure created as a result of the multi-stage influence of the Scandinavian ice sheet. Its most characteristic geomorphological feature are parallel sequences of land surface depressions, separated by local moraine hills.

The area in question covers the former German and Polish mine “Babina”, active between 1920 and 1972. Brown coal, ceramic clay and glass sands deposits were exploited with underground and opencast methods, resulting in a variety of anthropogenic transformations in the entire region.

The internal geological structure of the Muskau Arch, identified by drilling and mining works, indicates the presence of many zones, which differ in terms of the style of glacial-tectonic sediment deformation.

As part of the project, geophysical research (gravimetric and seismic) and geotechnical drilling were carried out providing new information on the character and scale of anthropogenic transformations of the glaciotectonic area, as well as the origins of anthropogenic and natural terrain deformations.

The developed gravimetric maps combine the geomorphological forms of the terrain and surface deformations with the geological structure and anthropogenic or natural changes. The qualitative interpretation is based on the analysis of the distribution, size and amplitude of gravity anomalies reflecting the bulk density of the sediments that make up the studied medium. Negative anomalies reflect the shortage of masses, which, as a natural factor, should be associated with the presence of weathering brown coal seams, their extent and dip. They are also generated by anthropogenic processes related to mining exploitation and translate into post-mining voids, zones of continuous consolidation and subsidence trough and post-mining heaps. Anomalies with positive amplitudes show the presence of tills, glacial sands and clays.

The results of measurements along seismic cross-sections confirmed the high glaciotectonic involvement within the Tertiary formations, showed the framework character of the top of the underlying (Cretaceous) deposits and allowed for the interpretation of lithostratigraphic boundaries.

Additionally, geotechnical drilling to a depth of 12 m was carried out in selected places using an impact system (Stitz) and a geotechnical light probe (Dynamic Penetration Light). The drillings were made in places that differed in the type of human interference: heaps, surface sinkholes, as well as in places intact by mining activities. The data from the drilling will be used for the geological and engineering analysis of morphological disturbances in the next tasks, including the construction of the model using the finite element method.

The natural and anthropogenic geomorphological forms of various origins that co-occur in the area of the UNESCO Global Geopark Muskau Arch constitute a part of the global geological and cultural heritage of a great importance in Poland and in Europe. Research which aim at discovering the genesis of these transformations can greatly contribute to our understanding of the modern-day environmental changes.