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

OBJECTIVES

OBJECTIVES The covered karst in the Northern Bakony Mountains had been studied for about twenty years. Findings were published in a series of academic papers. The present volume attempts to summarize karst processes and phenomena in the mountains. The contents are arranged around two topics. - Revealing covered karst development and covered karst phenomena in the Northern Bakony Mountains and - analysing the interactions between geomorphic evolution of and karstification on the blocks of the mountains; identifying types and subtypes of karstification. Rocks are eroded in two basic ways. On the one hand, corrasion affects rock masses through the action of various agents (water, wind, ice) which transport sediment load and, on the other, corrosion involves the partial or total dissolution of rocks and the removal of solutes. Non-soluble rocks, such as sandstones, granites and others, are primarily eroded by running water under temperate climates and V-shaped valleys are generally produced. Valley development may be controlled by crustal structure as in the case of valleys along grabens. Such valleys are called concordant, while for discordant ones evolution is independent of crustal structure. A group of discordant valleys is constituted by transversal valleys, which is a collective term for regressional, antecedent and superimposed types. With the retreating erosion of their water-courses, regressional valleys are increasing their lengths. Head valleys are gradually shifting upslope. The valleys are invariably younger than the elevations they are cut into. Antecedent valleys or valley sections are older than the elevations they are formed in. A section of the already existing valley undergoes uplift and incision may keep pace with it. As a consequence of increased relief, river energy accumulates and intense incision results in the formation of a steep-walled gorge. The speed with which the valley sides are shaped does not allow time for their lowering. Valley incision may be inherited from cover sediments over the underlying rocks. They are called superimposed (epigenetic) valleys. The planform of their channels preserves the shape adjusted to their mechanism before inheritance, eg. meandering. In case the underlying rocks are hard and resistant to erosion and, thus, valley walls are not lowering, superimposed water-courses also run in gorges. Inheritance often affects carbonate rocks (limestones or dolomites). If the cover rocks are removed from above carbonate sediments, the fluvial valley becomes an inactive dry valley. (Rainwater infiltrates into the easily permeable carbonate surfaces and, thus, the water-courses dry up.) The valleys in mountains of carbonate rocks are mostly of the superimposed type. Transversal valleys are often of complex origin. Regressional-superimposed and antecedent-superimposed valleys are also common in the Bakony Mountains. In the first case a regressional valley in the side of a block is inherited from the cover deposits (eg. gravels) over carbonate rocks and along a section terrain elevation was increased by the uplift of a (group of) block(s). Carbonates dissolve - primarily due to the influence of carbonic acid - without residue. Rock solution and the accompanying processes are called karstification. The resulting landforms are typical features of karst regions. The rainwater infiltrated into carbonate rocks percolates through fissures and cracks. As joints are widened by solution, water conduction capacity increases with time. Since water is conducted into depth, no drainage network develops on the karst surface and existing val-