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

KARSTIFICATION

Chimney development The upper parts of primary chimneys are filled by inwashed cover sediments. In the zone of filling development through solution stops as rock surfaces are sealed by a thin veneer of sediment. Below the zone of filling the chimneys and cracks further broaden through solution. The solution percolating through the fill does not saturate, its solution capacity can even increase with the uptake of biogenic CO

r Chimney formation is a particular manifestation of surface solution on covered karsts. the covered karst features associated with chimney formation are genetically analogous with solution dolines. With the solutional merging of primary chimneys a secondary or blind chimney forms (Pict. 4; Figs. 5, 6). In the rock, not only above and below the blind chimney but also around it, a zone of primary chimneys come about. The side-walls of blind chimneys are dissected by ruins of primary chimneys not affected by solutional merging (Picts. 5, 6). The infilled primary chimneys above blind chimneys may reactivate when the clay fill is redeposited from their lower part into the blind chimney. For this reason, blind chimneys develop towards the surface. Through the solutional merging of bordering primary chimneys they may also widen. Subsidiary blind chimneys may also develop when within the zone of primary chimneys around blind chimneys local merging occur by solution. Blind chimneys occur at the intersections of fracture planes or on rock boundaries. In the former case the stratification of the rock is less predominant and the dip of strata is low. In the latter case, the rock is well-stratified and the dip of strata is steep and the chimney itself becomes like a crack. The position of the developing landform accords with the spatial positions of the strata of the enclosing rock. Chimneys can also be composite. Then the chimneys developed at the intersections of fracture planes are connected by passages formed along bedding planes (Figs. 7, 8; Table I). The development of chimneys opening to the surface is accelerated by the growth of the duration of solution. It is promoted by the sediment accumulation in the surface depression which retards the rate of water recharge. Fig. 5. Development of covered karst blind chimney (VERESS-PÉNTEK 1995b) Legend: 1. carbonate rock; 2. permeable cover sediment; 3. soil; 4. redeposited soil and cover sediment in crack and chimney fill; 5. percolation; 6. rainwater; 7. chimney extension upwards through solution or collapse of dividing walls; 8. blind chimney broadening by solution of walls 9. water (solvent); 10. old dividing wall; 11. filled primary chimney, temporarily inactive; 12. unfilled active primary chimney; 13. biogenic CO

? uptake; 14. zone of primary chimneys, 15. blind chimney