Genesis of the Jaskinia Pod Świecami (Poland) – studies based on interdisciplinary geomorphological, geophysical and geodetic data / Bernadetta Pasierb, Grzegorz Gajek, Jan Urban, Wiesław Nawrocki ... więcej

Genesis of the Jaskinia Pod Świecami (Poland) – studies based on interdisciplinary geomorphological, geophysical and geodetic data / Bernadetta Pasierb, Grzegorz Gajek, Jan Urban, Wiesław Nawrocki // W: 14th International Symposium on Pseudokarst, Sudetes, Southwestern Poland, Karłów 24-27th May 2023 : abstracts [Dokument elektroniczny] / ed. by Jan Urban, Kacper Jancewicz. – Wrocław : Institute of Geography and Regional Development, University of Wrocław, 2023. – S. 48-49 : fot. – Tryb dostępu: https://14pseudokarst.wonders4you.com/wp-content/uploads/2023/06/Abstracts-fin-fin.pdf. – Bibliogr. s. 49. – ISBN 978-83-62673-85-8

The caves formation is a result of the interaction of natural processes such as karstification, erosion, weathering, suffusion, gravity induced processes and sedimentation, as well as anthropogenic processes. ... więcej

The caves formation is a result of the interaction of natural processes such as karstification, erosion, weathering, suffusion, gravity induced processes and sedimentation, as well as anthropogenic processes. The development of a cave is also influenced by rock properties (mineral composition, structure and texture, porosity) and state of its secondary alteration (infiltration, relaxation). These factors have been changing in time and space with varying intensity and have had a predominant or insignificant influence on the cave development. Owing to these processes, the interior of the cave has been modified. These changes include the cave environment, flowstone cover, cave sediments, as well as forms of cave relief, in particular the shape of the ceiling and floor, and rock structure in its surroundings. Their correct reading and interpretation with the help of specialized research make it possible to understand the speleogenesis. The paper presents the results of interdisciplinary research conducted in the area of the Jaskinia pod Świecami (Cave Under the Candles) formed in the Neogene (Miocene) calcarenites (Gubała, Kasza 1998). The study site is located in central Poland, in the Kielce Upland (342.3) within the Szydłów Foothills (342.37) (Solon et al. 2018). The aim of the research was to determine the cave's genesis based on geomorphological, geophysical (electrical resistivity tomography ERT and georadar GPR) and laser scanning (TLS) surveys, conducted on the surface and inside it. Observations of the cave's interior confirmed its complex genesis.
The present-day cave entrance is situated in the lowermost part of the abandoned quarry wall. It is narrow, partially covered by weathering material dropped from the top of the quarry wall. Behind the entrance is a relatively large chamber up to 8 m wide, sloping to the east. It is 50 m long and passes into the essentially horizontal passage. Both chamber and passage run along an uneven fissure (Fig. 1B) of the W-E direction. The other cavities of the cave are: a low passage, about 20 m long, running toward the north (perpendicular to the main passage), and a narrow passage, 8 m long, running westwards from the entrance chamber. Both of these passages were formed along cracks that are currently uneven and more or less weathered. Vertical tubular voids (called candles) as well as undulating weathering-erosion strips visible on the cave walls (Fig. 1A) evidence a rainwater infiltration and dissolution of calcarenites by underground waters. As a result of the TLS survey, good-quality 3D measurements of the cave geometry were obtained. According to the TLS studies, the length of the main passage, running W-E, is 46.5 m. This dimension is smaller than that resulting from geomorphological and speleological recognition (Gubała, Kasza 1998) by 11.5 m. The resulting difference in the dimensions of the cave may be due to the inability to carry out measurements in appropriate places. Due to the size of the device and the requirement to position each station, it was very difficult or impossible to acquire the point cloud from extreme locations in the corridors. The maximum height of the Jaskinia Pod Świecami based on the TLS measurements was recorded in the confluence zone of the corridors and is 3.6 m. ERT cross-sections visualized the shape of the cave under an almost 4 m thick overburden of clastic rocks (formed mainly of Pleistocene glacial till of the South-Polish glacial complex, with a small contribution of fluvioglacial and aeolian sands), and determined the locations and extent of heterogeneities present in the bedrock. Particularly a lot of heterogeneities – zones of inner rock cracking and loosening – were located in the near-surface layer to a depth of 1 m below the ground surface. As indicate ERT surveys, the recorded vertical voids (candles) are not associated with any rock structures, such as fissures, bedding (planes), etc., which confirms the statement of Morawiecka and Walsh (1997) and Walsh and Morawiecka-Zacharz (2001), that the candles developed owing to the circulation of aggressive, glacial water associated with local degradation of permafrost. Studies by Dobrowolski et al. (2007) prove that their development occurred during the anaglacial phase of this glaciation. Below the overburden, in limestone complex, a high resistivity anomalous zone was registered on ERT cross-sections, which imaged the cave along with the zone of cracks and fissures that developed around it. The fading crack zone was outlined quite deeply – up to the 18 m below the ground surface. The echograms obtained from the GPR survey also recorded near-surface zones of cracking and loosening, as well as zones of fissures formed around the cave. In particular, fissure zone is located near the abandoned quarry, near the cave entrance, and in the vicinity of the northern corridor. It indicates important role of karst-weathering processes in the cave development. On the echograms such zones are also present in the cave surroundings and in the distant part of the main cave passage, and its extension. The development of the cave took place as a result of the epigenetic (tectonic, deep weathering) loosening of the rock massif followed by karstification and anthropogenic activities characteristic of areas of intensive exploitation of rock resources. These two latter processes brought about collapses of detached rock fragments from the cave ceiling (Fig. 1B). It can be postulated that the most important initial process was a dissolution of the rocks below the present-day cave, while the subsequent gravitational collapses formed the present-day cavities.
The use of integrated geophysical methods not only confirms their effectiveness in mapping of caves, but also enabled a thorough and precise assessment of the processes occurring there, the degree of karstification and associated danger caused by the shallow near-surface occurrence of crack and void zones. In addition, under conditions of increased anthropo-pressure, there is a reasonable assumption that the development of the cave will determine the deformation of zone surrounding a cave, which will consequently lead to its further degradation contributing to the formation of superficial depressions.