Ľudovít Gaál’s research while affiliated with Detská fakultná nemocnica s poliklinikou v Bratislave and other places

Slovak Karst is the largest karst area in Slovakia and is considered as one of the most distinctive karst plateaus in Europe. The Slovak Karst consists of several carbonate block slices of the Silica Nappe of Silicicum Unit, lying on deep-marine rocks of the Turnaicum and Meliaticum units. Each of these blocks has an impermeable Werfen shale at the base, therefore, they form hydrologically individual, disconnected structures. The Slovak Karst is featured by a complete range of surface and subsurface karst landforms. Abundant karren, dolines, uvalas, blind and dry valleys, gorges, canyons as well as rare inactive poljes occur within the karst landscape. Subsurface karst phenomena are represented mostly by vadose vertical shafts and stepped abysses. Moreover, several epiphreatic horizontal and subhorizontal caves were developed due to the corrosive activity of autochthonous and allochthonous underground streams. At present, 1184 caves are known in the Slovak Karst. The vast majority of them is originated in the Pliocene and Quaternary. The oldest phase of karstification is associated with residues of the upper Cretaceous paleokarst phenomena. The subsurface karst phenomena of the Slovak Karst and the adjacent Aggtelek Karst in Hungary represent an unusual example of high variability of cave morphology and origin, carbonate speleothems as well as rare cave fauna and archaeological findings in the plateau karst of the temperate climatic zone. Therefore, they were declared as a part of the UNESCO World Heritage in 1995.KeywordsSlovak KarstKarst landscapePlateau karstKarrenDolineBlind valleyPaleo-poljeCaveAbyssPaleokarst

The Ochtiná Aragonite Cave (Western Carpathians) represents a unique natural phenomenon. It originated under particular lithological and hydrogeological conditions of the Ochtiná Karst in which several isolated lenses of Paleozoic crystalline limestone, partly metasomatically altered to ankerite, are enclosed by phyllites. Meteoric water seepage through non-carbonate rocks dissolved limestone and caused the oxidation of ankerite to Fe oxyhydroxides. Carbon dioxide produced during ankerite oxidation enhanced limestone dissolution. The maze cave consists of parallel fault-controlled linear passages and chambers interconnected by transverse horizontal passages. Phreatic and epiphreatic solution morphologies resulted from slowly moving or standing water. These include flat ceilings (Laugdecken), facets, lateral notches, convection ceiling cupola-shaped depressions, and spongework-like hollows. Flat ceilings were developed in several altitude positions, each of them probably closely below the slightly oscillated water table. Primary phreatic cupola-shaped depressions, truncated by flat ceilings, represent relics of the oldest cavities (pre-Quaternary? to Early Pleistocene). Inward-sloping smooth facets were not developed only in passages with flat ceilings, but also in the passages and halls with a vaulted ceiling. The asymmetrical shape of cusped depressions above the facets were documented in detail by a high-resolution cave topography with terrestrial laser scanning and digital photogrammetry. Middle-Late Pleistocene accumulation phases, identified by magnetostratigraphy of cave sediments and U-series dating of speleothems, are associated with phreatic and later epiphreatic development. The deposition on the bottom bedrock began before 1.8 Ma. The Brunhes/Matuyama boundary (0.773 Ma) and Jaramillo magnetozone (0.990-1.071 Ma) were recorded in the profile in the Oválna chodba Passage. Slow depositional rate (~0.09 cm/kyr) calculated from magnetostratigraphy resulted from slow water movement in confined conditions in marbles completely enclosed by phyllites and no direct relation to the surface. Only occasionally turbid water was loaded in extremely fine-grained infiltration material and autochthonous Fe oxyhydroxides. The depositional rate in Mn-rich layer was much slower (~0.03 cm/kyr). Additional U-series dating confirmed that old aragonite generations (with ages about 500-450 ka and 143-121 ka) were partly corroded by repeated floods during Late Pleistocene humid episodes. Aragonite younger than 13.5 ka is not corroded.

The Aggelek and Slovak karsts (Central Europe, Western Carpathians) represent a typical example of well-developed plateau karst in the humide temperate climate zone. Numerous surface and subsurface landforms (more than 1,400 caves) resulted from the high karstification of Triassic carbonates. Complicated multi-phase evolution of karst from the Late Cretaceous to the present is recorder in the morphology and sedimentary fills of caves. Mostly the variability of cave morphology and origin, carbonate and ice fills, as well as rare cave fauna and archaeological findings are extremely rich in this trans-boundary Hungarian-Slovakian karst area. Many abysses in high density were developed on the top of karst plateaus (up to 20 abysses on the area of 0.5 km2). The Baradla–Domica cave system is an excellent example of a fluvially modelled ‘ideal watertable cave’. Several multi-level caves formed by allogenic sinking streams on the edge of karst plateau or through valleys. The Domica Cave belongs to the most significance caves in the world with the occurrence of shields. The Baradla–Domica cave system hosts more than 500 animal species and played an important role in regional and global biospeleology. The Ochtinská Aragonite Cave is exceptional by very rich and varied aragonite forms of several generations, as well as remarkable solution morphology (mostly flat ceilings and inward-sloping facets). The Dobšinská Ice Cave in Slovenský raj (Slovak Paradise), is known by the largest volume of cave ice in the world (more than 110,000 m3), although it occurs in the mid-mountain position (its entrance lies at 969 m a.s.l.). The Silická ľadnica Cave is the lowest lying perennial ice cave up to the latitude of 50° north, in the temperate climatic zone. The Dobšinská Ice Cave is a unique site of European importance for hibernation of cold tolerate bat species as Brandt´s bat (Myotis brandtii) and whiskered bat (M. mystacinus). Many archaeological artefacts were preserved from the settlement of caves by man in the Palaeolithic, Mesolithic but mainly the Neolithic period. Also younger cave settlements are documented by rich artefacts. From a view of nature protection, the Aggtelek and Slovak karsts, as well as the associated part of the Slovenský raj above the Dobšinská Ice Cave and Stratenská Cave (genetically one cave system) occur in the territory of national parks or nature reserves. To enhance the protection of caves, buffer zones have been delineated in the catchment areas of caves that are threatened by allogenic sinking streams polluted due to agriculture, limestone quarrying or other negative human impacts.

The Zlejkova diera, located in the south-western edge of Štiavnické vrchy Mountains (The Krivín Natural Reserve), is a small syngenetic (primary) cave in the Miocene andesite lava flow. A smooth circumference surface of this quasi-ellipsoidal cavity (3.75 m long, 2.85 m wide, and to 1.75 m high) is formed by andesite showing a platy jointing (thickness of individual plates/slabs is 1 to 5 cm). The cupola-like vault from its highest point decreases asymmetrically to the lower part of walls – steeper towards the end and lateral edges of the cave, more slightly towards the recent cave opening to the surface. The rock floor is slightly inclined to the northwest where steep platy jointing at the walls joins the floor slabs. Based on preliminary results of the field research conducted in October and November 2018, the origin of Zlejkova diera can be explained as (1) a spherical pneumatogenic cavity (bubble cave) formed by gas expansion in the Miocene andesite lava flow below the top of its basal part (the upper part of the lava flow is formed by blocky lava), (2) a cavity formed by flowing lava which was moved beneath the hardened surface of a lava flow (platy jointing of andesite, less porous to non-porous lava) or (3) a cavity formed by a combination of both volcanic processes. Based on equally curved andesite slabs in front of the entrance, as well as the dip of andesite slabs on the ceiling at the entrance, it can be assumed that the cave was originally longer (the length of original cave was probably more than 8 m). Despite the need to resolve the origin of Zlejkova diera in more detail, it represents one of the sporadic cave genetic types in Slovakia.

The Moldavská jaskyňa Cave is the largest and most typical two-dimensional underground labyrinth in Slovakia. It was formed in Wetterstein Limestones, mainly due to the diffuse penetration and repeated flood injections of allochthonous waters from the Bodva River, and persistent ponded floodwaters in underground conduits. In relation to the uneven fracturation pattern in limestones, the cave is composed from an angular network and anastomotic-like, locally spongework segments. The former is predisposed on distinctive fractures, while the latter are predisposed mainly on less distinctive, small-scale discontinuities. Same as passages and halls of the cave labyrinth, small-scale phreatic and epiphreatic solution morphologies on the ceiling and walls (ceiling pockets, spongework cavities, paragenetic ceiling channels, rock pendants and partitions, inward-inclined facets, flat ceiling surfaces, water-table notches and some other forms) were sculpted in slowly flowing to stagnant waters. The bedrock floor is not visible in the whole cave, because it is covered by thick fine-grained allochthonous sediments (slackwater facies), in many places up to the ceiling. The Moldavská jaskyňa originated in the Late Pleistocene and Holocene, during several phases of erosion and accumulation in relation to the downcutting and aggradation of the Bodva river bed, lateral planation of the floodplain, and associated oscillations and stagnations of groundwater table, as well as repeated floods of underground passages and halls.

During the Alpine orogeny of the Western Carpathians, hypogene caves have originated in different settings and epochs. Several caves of hydrothermal origin in crystalline limestones and metasomatic secondary quartzites (metasomatic silicites) are known in the central zone of the Štiavnica stratovolcano, Štiavnické vrchy Mountains. The early phases of speleogenesis in the crystalline limestone near Sklené Teplice Spa were caused by post-magmatic dissolution linked either to the emplacement of subvolcanic granodiorite intrusions during Late Badenian time or to the spatially associated Late Sarmatian epithermal system. Speleogenesis in metasomatic secondary quartzites in the Šobov quarry is related to deep-seated hydrothermal processes associated with a diorite intrusion in the northern part of the central zone of the Štiavnica stratovolcano during its pre-caldera evolution phase in Upper Badenian. Unusual caves in metasomatic magnesite, with mineralogical evidences of their hydrothermal origin, were investigated in the Revúcka vrchovina Mountains. Paleokarst geoda-like cavities and small hydrothermal caves occur in nappe structures of Triassic carbonates that were uplifted within the Tatra-Fatra belt of core mountains (many of these cavities are integrated into younger and larger non-hypogene caves). Cavities with thermal water in underlying and faulted Mesozoic carbonates (covered by Neogene or Paleogene sedimentary rocks) were identified by boreholes in some intermontane basins (Rimavská kotlina Basin, Liptovská kotlina Basin). A phreatic shaft formed by progradational collapse of non-carbonate beds disrupted by artesian karstification of underlying carbonates occurs at Tornaľa Town in the Rimavská kotlina Basin. Several caves with hypogene morphologies have originated along marginal faults of horst structures or fault edges of horst–graben structures (speleogenesis by thermal or slightly heated ascending waters, but mineralogical evidences of hydrothermal karstification were not found). http://www.springer.com/gp/book/9783319533476

The Zápoľná Cave is located in the SW part of the Kozie chrbty Mountains in the valley of the Čierny Váh River. It is formed in the carbonates of the Gutenstein Formation, right above the décollement plane of the Svarín Partial Nappe (belonging to the Hronic Unit). The rocks bear marks of intensive brittle deformation indicating that the nappe emplacement occurred in relatively cold conditions. The fine-grained sandstone, considerably atypical for the purely carbonate Gutenstein Formation, occurs in the cave. It probably reflects the transition from the underlying siliciclastic Šuňava Formation, which most likely acted as a tectonic lubricant during the nappe translation, and is at present tectonically amputated from the Svarín Partial Nappe. The cave passages follow mainly faults or joints with two general types of orientation – the N–S direction and the E–W directions. Their contribution to the genesis of the cave was not only passive but also active, as they show the signs of the neotectonic activity. Based on the speleomorphological features, the cave evolution is divided into three phases: (I) deep in phreatic zone when the majority of the cave volume was formed by slowly circulating water along the discontinuities (mainly steep faults/joints) in the host rock; (II) in epiphreatic zone characterized by the appearance of the water table in the middle parts of the cave, and followed by its slow fall; and (III) in vadose zone after the water table decline, is characterized mainly by collapse processes. The evidence from cave morphology and flls suggests that there was no ponor through which the Čierny Váh River could enter the cave directly. The phases of the cave evolution, along with the activity of the E–W-trending discontinuities, could be linked to the activity of the Vikartovce Fault located in the south-eastern part of Kozie chrbty Mts., which was active up to Late Quaternary

The existence of underground karst cavities in magnesite deposits in Slovakia was indicated already at the end of the 1950s. Their speleological survey started only from 1983, when the caves were investigated in magnesite deposits Podrečany, Burda, Lubeník and Bankov in the Carboniferous rock belt 120 km long between Lučenec and Košice towns, located along the boundary zone between the Gemeric and Veporic tectonic units of the Western Carpathians in the Slovenské rudohorie (Slovak Ore) Mountains. Until now, altogether 16 caves in magnesite deposits were speleologically investigated and mapped in Slovakia. Except of one, all of them are accessible only from the mine workings. Generally their lengths are between 10 and 20 m but the longest cave reaches up to 73 m. These caves occur in Carboniferous magnesite-dolomite lenses surrounded by graphite-sericite schists or phyllites of the Gemeric Unit. As our research has manifested, the caves in magnesite originated due to the post-Upper Cretaceous shearing of the Alpine deformation phase AD3. Shearing during this deformation phase caused the origin of the penetrative NE-SW trending regional shear faults in the western segment of the magnesite bearing Carboniferous belt, encompassing the caves in the Podrečany, Burda, Lubeník and Dúbrava Massif magnesite bodies. In the eastern segment of the belt with the Bankov deposit the NW-SE trending faults of the AD3 phase were dominant. In particular cases, the faults of the AD3 phase may represent the reactivated discontinuities of earlier Alpine phases AD1 and AD2. The azimuth and dip parameters of the caves manifest that besides the main AD3 discontinuities, parallel with the shear faults, the extensional AD3 antithetic shears in-between individual shear faults have the supreme importance at the origin of the cave open spaces. Faults cutting the whole magnesite bodies allowed penetration of hydrothermal fluids throughout them. The fissures were widened by a hydrothermal karst process, accelerated by oxidation of Fe in the oxidation zone (FeO as an isomorphic admixture in the magnesite is represented app. by 3 %). Hydrothermal process related to the cave formation was caused by low-salinity fluids probably with progressively higher proportion of meteoric water and with the temperature less than 150 °C. In Neogene, after the first uplift of the magnesite bodies, the water level decreased in relation to the incision of adjacent valleys and the aragonite crystals and palygorskite started to crystallize in the vadose conditions. © 2017 State Geological Institute of Dionyz Stur. All rights reserved.