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

KARSTIFICATION

conduit may be occasionally preserved. A truncated feature is the Gyenespuszta Cave in the area of Hárskút (Pict. 2). The side slopes of the valley incising between cone rows (developing superimposed valley) are sometimes covered by loess (Fig. 50). Where loess is washed down and thins out, a hidden rock boundary develops and dolines with ponor and pseudoponors come about. The karst depressions are aligned in the valley sides in rows parallel with the valley axis. As a consequence of the removal of cover sediments, the hidden rock boundary and, thus, karstification shift upstream and solution dolines can also develop in valley sides without cover sediment. This variety of karstification is characteristic for the Öregfolyás Valley in the central Hárskút Plateau (Picts. 12, 14). Paleokarst depressions and karstification in their environs Karstification also results from the exhumation of paleokarst depressions of various size, shape and origin. They are eg. dolines formed before the present stage of karstification (allogenic type of karstification) and ponors formed at the beginning of the present stage of karstification (authigenic type of karstification). Ponors developed on valley rock boundaries in now inactive superimposed valleys. In this case, the valley was superimposed on a covered limestone terrain where the zone of flowing karst water lay close to the surface. On valley floors of this kind the uplift of the area resulted in true bathycaptures. Syngenetic karstification Karstification affects the thresholds between paleokarst depressions. The conditions are favourable for this process where the ponors formed (along a rock boundary) on the floor of the superimposed valley were buried before the present denudation. As a result of the removal or redeposition of sediments covering the valley floor, the valley floor remnants between former ponors karstified (Fig. 51). A row of dolines-with-ponor develops in the direction of the inactive superimposed valley, the background area of dolines-with-ponor are the filled paleokarst depressions. (The sediments on the sides of superimposed valleys in which valley formation once began are missing by now.) It is a common phenomenon that even recent karstic features on valley floor remnants have been fossilised by now.) This subtype of karstification is clearly detected on the floors of superimposed valleys of uplifted blocks (Középső-Hajag, Som Hill and Papod-Borzás). The removal of cover sediments from the paleokarst through sheet wash can be so intensive that on the edges (mostly on symmetric hidden rock boundary) syngenetic karstification begins (VERESS-FUTÓ 1990). Pseudoponors or groups of pseudoponors are often generated. Because of matter transport in depth pseudoponors generate clearly delimited catchments in the area of the paleokarst feature (Pict. 15; Fig. 52). In the well-developed regressional channels leading to pseudoponors a series of bathycaptures is detectable. The areas of this subtype of karstification occur in isolation (the Eleven-Förtés group of dolines on Kőris Hill and the pseudoponor G-6/b near Gombáspuszta in the central Hárskút Plateau). This karstification is typical of fossil dolines. During karst processes dolines-with-ponor develop in fossil dolines. This type does not occur independently. The resulting features appear in low density and mixed with landforms of other types of karstification. Features of such origin probably occur on the Tés Plateau and in the western Sűrű Mountain Group.