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

RESEARCH HISTORY

BERTALAN (1955) mentions surface karst landforms from many places (from the environs of Csesznek, Fenyőfő and Lókút) and calls them ponors. Occasionally he points to their origin in loess or to their transformation. (Around Lókút he describes senile ponors and one filled with sediment and being transformed into a doline.) VERESS (1982a) calls the covered karst depressions around Hárskút - using LANG'S (1962) terminology - dolines-with-ponors, allowing evolution into a ponor proper. Changing his opinion later, however, he claims that dolines-with-ponors cannot develop into true ponors, only the increasing activity of some varieties (VERESS 1986) manifest such a trend. A doline-with-ponor is a transitional landform of covered karst. Since dolines-withponor do not form along rock boundaries as conventionally described in karst research (JAKUCS 1968, 1971a; HEVESI 1980, 1986) and, thus, they are not true ponors. At the same time, they are not typical dolines either since they have a water conduit function. Their development does not take place through surface erosion characteristic of dolines (JAKUCS 1980; ZÁMBÓ 1987, 1993; VERESS-PÉNTEK 1990, 1996) since they continue in well developed chimneys of corrosion origin in carbonate rocks. The corrosion origin of chimneys excludes erosion, ie. the erosional stage of development typical of conduit passages belonging to ponors formed along rock boundaries (JAKUCS 1971a). As a consequence of bathycapture (JAKUCS 1971a), the evolution of surface valleys on typical allogenic karsts is displaced underground but it is not observed for dolines-with-ponor. Even if this covered karst landform develops on the valley floor, it contributes to further valley evolution in the way that runoff on the valley floor reaches the chimney and increase the rate of dissolution. Over valley floors of gentle slope with loess fill conditions do not favour the erosional development of chimneys. This landform type is widespread in the mountains. Classifying surface karst features, HEVESI (1991b) distinguishes between blind valleys ending in loess, in red clays and in subjacent ponors and dolines (Nagy-Som Hill) and shallow incipient dolines (on the Tés Plateau). In author's opinion the reasons for classifying covered karst depressions of „doline-withponor" type either as ponors or dolines can be the following: - It was not recognised that surface karst features are not formed along rock boundaries. - The sediment accumulation at the bottom of karst features often made them similar in shape to dolines. The morphology, activity, evolution, filling deposits and origin of covered karst landforms are studied by FUTÓ (1980a,b); VERESS (1982a, 1984a, 1986, 1987a,b, 1995); VERESS-SAJTOS-FUTÓ (1990); VERESS-PÉNTEK (1995a,b). In recent years mostly manuscript reports were prepared on covered karst objects not yet described or inventoried from various parts of the mountains (KÁRPÁT 1974,1977, 1978a,b, 1979, 1980; SZOLGA 1975, 1979; Alba Regia BKCs. 1976a,b; NÉMETH 1976, 1989; Kocsis 1979; VERESS 1979b, 1980c, 1981b,c, 1984b; VASKOR 1983, 1986, 1988; JAKAB 1986; ESZTERHÁS 1985). Several authors have described area of interior or poor drainage from the mountains (GERGELY 1938; LÁNG 1958; SZABÓ 1966), which are more extensive compared to karst features. A common characteristic of these areas that they may include several covered karst features. They are common on dolomite terrains but also occur on limestone. Certain terrains with no drainage are described as paleopoljes by SZABÓ (1966). The survival of old poljes exclusively through inheritance is not very probable and they are supposed to be rather rare landforms. A more common way for the development of such features can be compaction and material removal in depth accompanying recent karstification in the study area (VERESS 1998).