Zarovnané skalné podlahy v jaskyniach

0509801 - GLÚ 2020 SK slo J - Článek v odborném periodiku
Bella, P. - Bosák, Pavel
Zarovnané skalné podlahy v jaskyniach.
[Flat solution bedrock floor in caves.]
Aragonit, časopis Správy slovenských jaskýň. Roč. 23, 1-2 (2018), s. 25-29. ISSN 1335-213X
Institucionální podpora: RVO:67985831
Klíčová slova: karst geomorphology * cave morphology * planar bedrock floor * cave bedrock terrace * lateral erosion * river cave * sulfuric acid cave
Obor OECD: Physical geography

Zarovnané skalné podlahy ako morfologické indikátory hydrografického vývoja jaskýň predstavujú špecifické, menej často sa vyskytujúce, avšak významné tvary jaskynného skalného reliéfu. Zarovnané skalné podlahy, prerušené výtokovými štrbinami, nechýbajú vo väčšine hypogénnych sulfurických jaskýň (u nás sa zatiaľ zistili iba na západnom okraji Plaveckého krasu – v Plaveckej jaskyni a jaskyni Pec, zväčša sú však pokryté jemnozrnnými sedimentmi z mladších vývojových fáz).

Flat bedrock floors as morphosculptural shapes formed by lateral erosion belong to important morphological indicators of the origin and development phases of caves. In river caves, flat bedrock floors resulted from lateral enlargement of passages by meandering underground streams, alternatively by two-sided extending or one-sided moving riverbed. In sulfuric acid caves, they are formed by intensive solution of limestone walls by sulfuric acid at or near water-table. Because the amount of dissolved oxygen decreases with depth below the water table, shallow pools on sides of fissure discharge feeders allow the formation of sulfuric acid by oxidation of H₂S dissolved in ascending fluids, which rapidly dissolves the limestone bedrock (Egemeier, 1981; Hill, 1990; Palmer and Hill, 2005; Palmer, 2013 and others). It was dissolved mostly on the inclined floor surfaces of wall notches, when water film was flowing down after repeated drops of water table. Due to greater water movement, the oxidation is most rapid where the floor gradient is steepest and slowest where the gradient is flattest (Egemeier, 1981). If flat bedrock floors are covered by fine-grained sediments, they protect underlying limestone from dissolution (Hill, 1990). In these cases, the flat floor is laterally enlarged to both sides. Smooth ‘corrosion tables’, described by Audra (2008), Audra et al. (2009), and De Waele et al. (2016), formed by acid condensation waters (condensation sheet-runoff) flowing back to the feeding fissure or pool. If flat solution floor surfaces are laterally associated with wall water-table notches, their origin can be rather linked with water table and its repeated slight oscillations. In Slovakia, flat solution floors resulting from sulfuric acid speleogenesis were documented in hypogene caves on the western fault marginal part of the Malé Karpaty Mountains (Plavecká jaskyňa, Pec). Remnants of older flat floors, in river as well as sulfuric acid caves, are preserved as terraced surfaces at the edges of cave passages or halls. Many flat solution floors are integrated parts of cave levels formed in relation with the stable erosion base on the surface. Therefore their formation can be correlated with the formation of adjacent planar landforms (river terraces, planation surfaces). If sulfuric caves or hypogene caves with sulfuric development phases are controlled by significant faults in the marginal parts of horst mountains, flat solution floors and subsequent cave levels can be used to the reconstruction of the phases of interrupted subsidence of adjacent basins/grabens. In caves where flat solution floors have originated in relation to a local lithological threshold, i.e. internal erosion base, they can not be correlated with other planar landforms.
Trvalý link: http://hdl.handle.net/11104/0301152