hrvatski

Denudation of dolostone karst, the case of Eagle Cave system (Spain)

volution of cave systems is in great extent impacted by rock weathering. These processes include widening of cave passages and collapse of blocks from cave ceilings. Denudation of the surface above cave system additionally enhances thinning of bedrock above caves, favouring the cave ceiling collapses. These processes result in exposure of cave passages to the surface and formation of unroofed caves. In the area of Eagle Cave, in central Spain, collapse breccias and flowstone speleothems exposed at the surface indicate the existence of unroofed caves. The cave has a main hall where subsidence and ceiling collapses are ubiquitous, showing that collapses, whether they result in unroof caves or not are common. To quantify the denudation rate on the region, we measured denudation rate using rock tablet method at this location. Depending on the lithology that composed the cave bedrock the denudation rate varied between 1.75± 0.66 and 2.48 ± 1.07 μm/yr. However, dating of speleothems exposed to the surface (outside the cave) in unroof caves around Eagle Cave, provides dates as young as 213 ka BP. This is surprising, since apart from existence of speleothems exposed at the surface, cave morphology of the unroof caves is completely lost, supporting a very dynamic process of destruction of cave galleries. The denudation rate calculated by the rock tablet method seems to be too small even to eliminate the collapse blocks of a thin ceiling over the studied speleothem. As previously highlighted in previous studies, different methods to estimate denudation rate provides results that differ in orders of magnitude. Our result supports such conclusions. Therefore, the main goal of this ongoing research is to apply different methodologies to measure denudation rates, compare their results and estimate which are the benefits and problems that the different methods are providing. As well to improve our understanding of karst denudation rates and the accuracy of the methods used for their evaluation. Acknowledgements: This research is a part of the research project “Inter-comparison of karst denudation measurement methods” (KADEME) (IP-2018-01-7080) financed by Croatian Science Foundation.

denudation, cave, karst, dolostone, KADEME

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