Development of Epikarst and Dolines in the Bakony Region (Hungary)

The relationship between the epikarst and subsidence doline development is studied on five covered karst terrains of the Bakony Region with the use of bedrock resistivity. Average resistivity was determined by karst areas based on the resistivity data of geoelectric-geological profiles, then the relationship between the resistivity of the bedrock below the dolines of the profiles and the average resistivityaverage resistivity of the bearing profiles was studied. It can be established that at sites where more water gets into the karst, the averages of resistivity are low (the epikarst is more mature), where less water arrives there, the averages are higher (less mature epikarst). The dolines of the studied areas can be put into five groups. Dolines belonging to groups A and B are those at which more water gets into the karst, below them, resistivity is lower on the bedrock and the epikarst is more mature. Groups C and D involve dolines, at which less water gets into the karst, below them, the resistivity is higher in the bedrock and the epikarst is less mature. However, below dolines that belong to groups A and C, resistivity is higher as compared to their environment since there are more infilled cavities. At groups B and D, the resistivity is lower below the dolines than in their environment as a result of the larger number of filled cavities. The fifth group (group E) is the final phase of doline development when the shaft of the doline develops. During doline development, dolines belonging to group Agroup A take up the characteristics of group Bgroup B, while the dolines belonging to group Cgroup C take up the characteristics of group Dgroup D. The majority of dolines develop above the bedrock mound since thin cover favours epikarst development below the doline. More mature epikarst with many cavities enables suffosion of larger degree and thus, doline development. In the case of those that were formed above bedrock depressions, due to larger cover thickness, the epikarst does not develop here, but it is formed next to the depression where the cover is thinner (more water gets into the epikarst, it is more mature and its resistivity decreases), then the water infiltrates below the bedrock depression and triggers cavity formation in the bedrock and thus, suffosion.