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

KARSTIFICATION

Fig. 19. Half-enclosed pseudodepression (environs of karst object Mb-20, Mester-Hajag) Legened: 1. contour line; 2. cover sediment; 3. semiexhumed cone; 4. pseudodepression; 5. karst depression (doline-with-ponor) The postgenetic karst featrures of depressions are the following (Fig. 23). If the paleokarst feature is of small dimension, over most of its area cover sediments acquire lower and lower positions. This way subsidence pseudodolines (with no water conduit on the floor) or dolines-with-pseudoponor (with water conduit on the floor) develop (Pict. 18,19, 20). The subsidence pseudodolines and dolines-with-pseudoponor do not have sharp edges. In their interiors, however, the internal depression formed by subsidence or caving is marked. The wall of the internal depression is of unconsolidated deposits. The floor is flat and rather extensive. After subsidence, the outer part of the depression is deepened by sheet wash. The karstic rock may outcrop locally. If the redeposition of sediment to the passage is limited, subsidence is restricted and slow. In this case the subsidence doline does not have a distinct internal part and a shallow and gently sloping depression ensues. Such depressions are never similar to blind valleys. It is common that for the internal depression or from the passage exposed on the floor an erosional channel retreats to the edge of the outer part. In this channel small depressions can form in the sites of pseudobathycapture (Pict. 21). Probably, they can be both syngenetic and postgenetic. The edges of internal depressions are often dissected by arcuate and steep features. They are produced by mass movements (of rock and earth falls); some of them, however, could be resculpted by sheet wash. Subsidence pseudodolines and dolines-with-pseudoponor are the largest surface karst landforms in the mountains. If the paleokarst landform is of great dimension, the filling sediments subside or cave in only partially. The clearing of an old passage is probably an indirect cause of the local caving of cover sediments. Because of the matter deficit in the passage another passage forms