Veress Márton: A Bakony természettudományi kutatásának eredményei 23. - Covered karst evolution... (Zirc, 2000)

KARSTIFICATION

Fig. 11. Varieties of subjacent dolines and their origin after BULL (1968) and formation of subsidence dolines after BÁRÁNY-JAKUCS (1984) (b) Legend: 1. limestone; 2. cohesive non-karstic rock; 3. permeable (cohesive or non-cohesive) non-karstic rock; 4. cave; 5. collapsed material; 6. water percolation; 7. material deficit caused by solution; I-III. phases The chimneys of the covered karst depressions in the mountains did not form along a rock boundary and thus they are not of erosional origin. They cannot be referred to any of the above mentioned types of karst doline either. In the covered karst landforms of the study area the genetic properties of the individual doline types occur in a mixed form. Against the erosional origin of dolines the following arguments can be cited. - The walls of the chimneys are overwhelmingly characterised by solutional features (Pict. 3). - The chimneys are narrowing downwards and becoming impassable or separate into passages of smaller diameter (primary chimney). If the chimneys were of erosional origin, they should be associated with through caves or continue in subhorizontal cave passages. This is not the case and it could be explained by the insufficient or ineffective exploration of caves. Chimneys would not narrow down in the enclosing rock (as it is often observed) but in the sediment fill. - In the environs of covered karst depression not located on valley floors the cover sediment is loess. In case of intensive water movement (a precondition of erosion) loess could not have been preserved on these terrains or only remnants could have been observed now. Today and even more so in the past, it is first of all loess and soils that are removed from the environs of covered karst dewpressions. Such materials are not suitable for efficient mechanical corrasion. - The covered karst depressions are almost always show deep fills. The transported sediment can only reach the chimneys if they are open for short intervals. From the flood ponds (see below) of covered karst depressions formed during activity the coarser sediment load, more prone to erosion, deposits and the already deposited sediments seal the chimney and hinder the movement of later transported sediment. - To several covered karst depressions no channel leads. In lack of channels such depressions cannot collect considerable amounts of water.