Veress Márton: A Bakony természettudományi kutatásának eredményei 23. - Covered karst evolution... (Zirc, 2000)
KARSTIFICATION
KARSTIFICATION Recent surface landforms in the mountains could develop independent of flowing karst water or their origin was bound in some way or another to karst water or to cavities formed by karst water. COVERED KARST FORMATION INDEPENDENT OF FLOWING KARST WATER Since water infiltrating from the surface and seeping through cover sediments motivated their development, karst features independent in their origin from flowing karst water came about through processes of hidden karstification. Cavitation due to flowing karst water can take place even under permeable cover sediments. The terrains covered by permeable sediments, where underground karst processes could or can be active are the buried karsts of the Northern Bakony. Rock boundary and karstification On buried karsts allogenic karstification can take place where carbonate rocks outcrop from below non-karstic cover sediments (unhidden rock boundary). Hidden karstification occurs where partly or entirely permeable cover sediments thin out to the extent that the percolating waters from surfaces at least partly covered by impermeable cover sediments (further: solution) is still capable of solution when reaches the karstic rock (hidden rock boundary). At the places where permeable cover sediments are thinning out, karstification is promoted by the following factors. - Loess decalcifies in the vicinity of the surface. Thus, where it is thin, there is no or hardly any CaC0 3 . Where loess is thicker, decalcification cannot be so intensive at lower levels. Therefore, under thicker loess series the solvent is hardly capable of dissolving the rock. - At the beginning of accumualtion on the uneven carbonate surface, there is material transport from more elevated surface to lower-lying ones. Therefore, thinner covers are richer in clay. Piping adds to impermeability and it is also stronger in thicker loess mantles. Infiltrating water moves partly laterally in thick loess towards areas with thinner loess cover. Where loess is thinner, water collects not only from vertical infiltration but also from lateral seepage. Thus the buried elevations of the carbonate surface become sites of concentrated solvent recharge. - It seems probable, however, that, in spite of this, where cover sediments are thinner, the limestone may also be affected by karstification but the resulting passages are filled by cover sediments. Therefore, the thicker are cover sediments, the shallower depression - possibly with outlet - can develop on the surface of the cover sediment. For this reason, most of the rainwater keeps on running off on the surface. Consequently, in the environs of the site where cover sediments are thicker, geomorphic evolution does not favour increased infiltration into the karst and this results in the stagnation of karst processes and in a final halt of karstification. The intensity of karstification along hidden rock boundaries considerably depends on the recharge of water. This latter factor, however, is a function of the impermeable nature of the neighbouring surfaces. The growth of impermeability with time may be caused the already mentioned process of loess decalcification, compaction through piping and reworking. The spatial variation of impermeability results fro the occurrence of loess locally under the Csatka Gravel Formation or the variable contamination of the carbonate rock, but the intercalation of non-karstic rocks outcropping to the surface may also lead to increased impermeable character. Tectonic circumstances explain why Requienian limestone and
