« Back

Abstract: Detailed geomorphological mapping on the carbonate terrain between Sopron and Lake Fertő found unusual, active depression systems. The landforms such as complex systems of nearly cylindrical structures, collapse dolinas and small caves remind to karstic forms. Near-surface geology was also reviewed in connection with these landforms and the detailed geological map of the area was compiled. The physical and geochemical properties of the near surface Badenian and Sarmathian Lajta limestone made the assumption of the karstic origin questionable. The main aim of this paper is to prove the origin and assess the future evolution of the landforms. In lack of evidences of karstic or non-karstic origin underground cavity (voids) and fracture systems – possibly connected to these landforms – were investigated on the basis of electromagnetic properties of the subsurface. The applied geoelectric and electromagnetic methods indicated the cavity but no connections were found with the fracture zones. According to the geoelectric tomography image of the test area the cavity is probably anthropogenic rather than natural in origin. Results of geophysical exploration were checked and evaluated by partial excavation of the subsurface formations and structure of the study site. Resolution power and proper scaling of different methods were also discussed. Finally, industrial archeology documents were taken into account. Number of medieval archeological records also supports the artificial origin assumption. Importance of holistic approach is emphasised in such complex cases.

Keyword: carbonate terrain, Lajta limestone, dolina, underground cavity, bedrock, geoelectric properties, GPR, resistivity sounding, industrial archeology, holistic approach