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

METHODS

oblique sections (developed along bedding planes) and vertical ones (developed along fractures). Comparative statistics of alignments of cave remnants and dips of enclosing rock strata Most of the cave remnants in the valley sides around Csesznek were formed along bedding planes. The frequency distribution of differences between cave alignment and dip direction were calculated for 66 caves. The %

2 test of the obtained data was made by BARTA. The question was asked: among the cavitation alignments directed along dip (0° difference), along strike (90° difference) and opposite to dip (180° difference) which are accidential and which are regular. It is remarked that the 0° difference category included values from 0 to 60°, the 90° category those between 60 and 120° and the 180° category direction differences of 120-180°. The calculations resulted in a 99.0 per cent probability of 0° direction difference compared to 90° and 99.9 per cent probability compared to 180°. 0° direction difference has a significant frequency compared to the other two direction differences. The direction difference 90° does not have a significant frequency compared to 180°. Therefore, the water dissolving caves in the valley sides around Csesznek must have arrived from the direction of their entrances. Since they open to valley sides, it is claimed that the rocks (and their cavities and cave sections) along whose bedding planes waters produced cavities have been partly removed by erosion. Consequently, the caves formed through the exposure of enclosed cavities. Direction frequency investigation of collapse dolines The collapse dolines of Dörgő Hill and Szent László-erdő are classified into circular, elongated wide and elongated narrow collapse dolines. The circular collapse dolines (n=22) are located close to the rock boundary between Middle Eocene limestone and Triassic „Hauptdolomit". The elongated wide (n=10) and the elongated narrow (n=6) collapse dolines are further away from these rock boundaries. The widths and alignments of collapse dolines points to the widths and alignments of cavities from which they developed. Cavity width and alignment, however, indicates current conditions of the karst water producing the cavities. The widths of cavities (collapse dolines) reflects a plan view of karst water movement, while their alignments a cross-section. The widths of collapse dolines decrease away from the outcropping rock boundary. The reason for this is that in the vicinity of the rock boundary karst water movement is horizontal, while it is gradually becoming subvertical moving away from the boundary. During horizontal movement broad and low cavities form due to dissolution along bedding planes and along the boundary of Middle Eocene limestone and dolomite. Vertical water current produces narrow but high cavities through dissolution along fractures. The flow system can be explained in the following way. The flow directions of karst water near the actual surface are closely determined by the relief between the terrain surface and the dolomite surface. The less cavernous dolomite has a lower permeability and, therefore, closer to its surface the karst water in the cover sediment would increasingly flow in lateral direction. Since the Triassic dolomite surface is rather uneven, the dolomite surface sinks lower and lower below the terrain surface moving away from the surface outcrop (rock boundary) and, parallelly, the nummulitic limestone cover grows ever thicker. (Assuming a