Acta Carsologica

ISSN 0583-6050

Contact: Andrej Kranjc kranjc@zrc-sazu.si

Website: http://www.zrc-sazu.si/izrk/carsologica/

Badino G. 2005. Underground drainage systems and geothermal flux

Acta Carsologica, 34 (2), 277-316. ISSN 0583-6050.

An analysis of the interaction between the geothermal flux and the water or air- deep drainage networks. The problem of geothermal power intercepted by deep structures and, in general, the temperature field calculations, is converted to classical thermo-engineering problems in terms of shape factors. It is shown that the fluid flow in a conduit perturbs the whole deep rock temperature field until the geothermal flux of a large area is focalised onto the conduit. It is shown that either small water masses flowing into a mountain are able to perturb the rock temperature up to the surface, on sizes that do not depend on water mass dimension, but on its depth, and then on enormous volumes. The introduction of the “geothermal cross section” of an underground drainage structure allows us to improve the classical formula of minimum provenance depth of geothermal water. Enlarging factors are applied to the classical estimation in dependence of the ratio between the actual average discharge and the critical discharge Qc, which depends on the conduit geothermal cross section. The geothermal “umbra cones” created in the overlying rock by deep underground structures are described. It is shown that the geothermal flux can play a significant role in the underground drainage phenomenology.

Dreybrodt, W., Gabrovšek, F., Perne, M. 2005. Condensation corrosion: A theoretical approach.

Acta Carsologica, 34 (2), 317-348. ISSN 0583-6050.

Condensation of water from warm, humid air to cold rock walls in caves is regarded to play a significant role in speleogenesis. The water condensing to the cave walls quickly attains equilibrium with the carbon dioxide in the surrounding air, and consequently dissolves limestone or gypsum forming various types of macro- ,meso-, and micromorphologies. In this paper we present the basic physical principles of condensation and give equations, which allow a satisfactory estimation of condensation rates. Water condensing to a cooler wall releases heat of condensation, which raises the temperature of the wall thus reducing the temperature difference ΔT between the warm air and the cave wall. Furthermore one has to take into account the heat flux from the air to the cave wall. This defines the boundary conditions for the equation of heat conduction. For a constant temperature of the air initial condensation rates are high but then drop down rapidly by orders of magnitude during the first few days. Finally constant condensation rates are attained, when the heat flux into the rock is fully transmitted to the surface of the karst plateau. For spherical and cylindrical conduits these can be obtained as a function of the depth Z below the surface. When diurnal or seasonal variations of the air temperature are active as is the case close to cave entrances, condensation rates can become quite significant, up to about 10-6 m/year. The theoretical results are applied also to corrosion of speleothems and the formation of »röhrenkarren« as described by Simms (2003) . To convert condensation rates into retreat of bedrock the saturation state of the solution must be known. In the appendix we present experiments, which prove that in any case the solution flowing off the rock is saturated with respect to limestone or gypsum, respectively.

Mocchiutti, A., Maddaleni, P. 2005. Chemical, geomechanical and geomorphological aspects of Karst in sandstone and marl of flysch formations in north east Italy.

Acta Carsologica, 34 (2), 349-368. ISSN 0583-6050.

Geomphology, geomechanical and geochemical features of some caves in flysch sediments in Prealpi Giulie, Friuli, North east Italy are described.

Parise, M., Trocino, A. 2005. Gypsum karst in the Crotone province (Calabria, southern Italy).

Acta Carsologica, 34 (2), 369-382. ISSN 0583-6050.

The Calabria region of southern Italy presents remarkable examples of gypsum karst, involving evaporite rocks ranging in age from Trias to Miocene. Triassic evaporites are limited to a sequence of about one hundred meters of thickness in the Coastal Chain, on the western Calabrian coast. Messinian evaporites, on the other hand, extensively crop out to the east, in the Crotone Basin. The present contribution intends to describe the main features of gypsum karst in the latter area, from the surface karst morphology to the development of caves. The Crotone Basin is among the most interesting areas as regards evaporite karst in Italy: a variety of surface karst landforms is there present, including dolines, blind valleys, closed depressions, and deep and narrow canyons intensely affected by slope movements. Many caves are located at the bottom of the dolines, as Grave Grubbo which, with a length over 2,500 meters, is one of the longest Italian caves in evaporites. The study area has experienced several transformations, mostly due to agricultural activity and to scarce attention paid by local administrators toward this unique naturalistic landscape. The high value of Calabrian gypsum karst is thus not fully exploited, and several cases of degradation of the caves have been registered, even with consequences for the quality of water flowing in the karst systems.

Häuselmann, P., Tognini, P. 2005. Kaltbach Cave (Siebenhengste, Switzerland): Phantom of the Sandstone?

Acta Carsologica, 34 (2), 383-396. ISSN 0583-6050.

Kaltbach cave is developed within the Eocene Hohgant sandstone in the Siebenhengste area in Switzerland. A remapping project of the cave resulted in a huge increase in length. It also produced a complete, updated map and longitudinal section. The cave's morphology does not fit with the "normal" speleogenesis: it is a so-called phantom cave. Phantoms are created by differential weathering of impure limestone under a preferably warm climate and a very low hydrologic gradient. Once the gradient steepens, the undissolved residual sediments are piped out; the "cave" manifests itself. The paper discusses the geomorphological features that permit to recognize the phantom caves.

Móga, J., Németh, R. 2005. The morphological research of the Basalt and Loess covered plateaus in the Bakony Mts. (Transdanubian Middle Mts. – Hungary).

Acta Carsologica, 34 (2), 397-414. ISSN 0583-6050.

We have conducted our morphological researches on the loess-covered Tési plateau and on the basalt covered karst area around Mt. Kab in the southern part of the Bakony Mts. The nearly 600 m high basalt covered Mt. Kab emerges high from the undulating mountains and hilly areas of the Southern Bakony Mts. Its surface, an area about 35-40 km² is covered by basaltic rocks of different thickness. Pseudokarstic landforms (depressions) developed on the basalt surface due to the carstic corrosion of the buried limestone layers. Grouping the objects of different morphology and evolution rate, and studying in corellation the genetic marks of the significant groups, a special karst process can be drawn, in which the depressions of various form can be understood as different stations of the same evolutionary series. The Mesosoic rocks building up the 60 km² Tési plateau emerge to the surface rarely above the loess cover. There is agricultural activity on most part of the plateau. Typical covered karstic landforms developed on the 3-5 m thick loess cover. Subsidence dolines or alluvial steamsink dolines with a small catchment area were formed on the summits. We studied the processes, forms and occurrence of recent covered karst of Mt. Bakony, and these studies shows that on the covered karst surface of the Tési-plateau the recent pit formation along with baticapture connected to hidden and real rock boundary, as well as the opening and activation of paleokarstic passages developed before loess formation also play a role in the evolution of the covered karst surface forms of the Tési-plateau.

Self, C.A., Mullan, G.J. 2005. Rapid Karst development in an English Quartzitic Sandstone.

Acta Carsologica, 34 (2), 415-424. ISSN 0583-6050.

Many karst features, including caves, have been found in the outcrop of the Fell Sandstone in Northumberland, England. These features are Holocene in age, since the area was glaciated during the Devensian cold stage. It is suggested that tectonic inception and selective arenisation of rock faces that remain damp are responsible for these karst features. The limitations of textbook definitions of the term karst are discussed.

Knez, M., Slabe, T., Šebela, S. 2005. Smoganica – a cave developed in upper Cretaceous breccia.

Acta Carsologica, 34 (2), 425-438. ISSN 0583-6050.

On the Banjšice plateau (NW Slovenia) the longest spring cave is 492 m long Smoganica. The cave (505 m above sea level) is situated on the SW slope of Čukla (770 m) E from the Soča river (153 m above the sea level). Smoganica is developed in limestone breccia, which is 10 m thick and belongs to the Upper Cretaceous flysch rocks. On the territory around the cave, the green marls are included in breccias or breccias are included into the green marls. Clasts in coarse-grained breccia, in which the cave is located, vary from some cm to several 10 dm in diameter. Clasts are mostly deriving from younger rudist limestones, Lower and Upper Cretaceous and Jurassic micritic and oolitic limestones. Smoganica is situated about 2 km south from Idrija fault and about 200 m north from Kobarid fault. There are two principal fissure orientations in the cave, N30-45ºE and N120-135ºE. Smoganica was formed from the system of smaller passages that have been developed inside the breccia in 3D. The cave was formed in phreatic conditions, later it was completely filled with cave sediments. In the next stage the above-sediment rock forms were developed. Cave sediments were later removed from the cave. Today the active water stream is cutting rock forms in the bottom of the cave passages. Higher water quantities are forming scallops and potholes and lower quantities floor channels. Smoganica can be described as polygenetic cave because the percolating water is reshaping the passages.

Ferrarese, F., Sauro, U. 2005. The Montello hill: The “Classical Karst” of the conglomerate rocks.

Acta Carsologica, 34 (2), 439-448. ISSN 0583-6050.

The Montello hill is, probably, the most typical morphounit between the karsts developed in conglomerate rocks. It may be considered the classical karst of the conglomerates comparable with the Classical Karst of limestones: the Carso of Trieste. The Montello hill consists in an elliptical plan figure, elongated for about 13 km in a WSW-ENE direction and a width of about 5 km. The rock unit involved is the “Conglomerato del Montello” of late Miocene age (Messinian), mostly composed by carbonate pebbles bound by a calcitic cement, which is 2000 m thick. The Montello is shaped by a complex system of fluvial planation and incision forms in which are distinguishable a main plateau and a stairs of seven planation rock cut terraces. The terraces are cut in the slope of a dead antecedent valley. On the fluvial planation forms dolines, mostly of the drawdown type but also of the point recharge type, have evolved. In total more than 2000 dolines are present. In the seven rock cut terraces the dolines show different development and dimensions according with the ages of the surfaces. In the first morphogenesis of these dolines and of the caves the control of the plan structures as the bedding surfaces and the fractures seems to have been feeble; on the contrary the porosity of the conglomerate has been a determinant factors for the developmente of the karst drainage.

Lepirica A. 2005. Basic morphological and morphostructural characteristics of the Rakitnica canyon (Dinaric Karst, Bosnia and Herzegovina).

Acta Carsologica, 34 (2), 449-458. ISSN 0583-6050.

The canyon valley of the Rakitnica river is one of the deepest and longest in the Dinaric karst. The paper states the basic morphological and morphostructural characteristics of the canyon, and gives its geomorphological regionalization. High level of correlation between lithology, tectonics and relief of the researched area has been determined. Genesis and development of this relief form have been considerably guided by neotectonic processes during the Quaternary.

Al-Malabeh, A., Kempe, S. 2005. Origin of iron ore nuggets (“Bohnerze”) through weathering of basalt as documented by pebbles from the Herbstlabyrinth, Breitscheid-Germany.

Acta Carsologica, 34 (2), 459-470. ISSN 0583-6050.

This study was conducted to investigate the origin of the iron nuggets that have been found in the Herbstlabyrinth at Breitscheid, northern Hessen/Germany. A total of ten pebbles were collected. Petrographically, the pebbles can be divided into three groups: rather fresh basalts, markedly or totally altered basalt (including the iron nuggets) and a dark sandstone. The iron nuggets originate through a progressing alteration (oxidation and hydration) of the basaltic pebbles. The geochemical study shows that the original fresh basaltic pebbles are of alkali type and belong to the Na-series. The magma that gave rise to them was primitive and originated in a mantle peridotite mantle source.

Šebela S. 2005. Monitoring of active tectonic structures – Project COST 625.

Acta Carsologica, 34 (2), 471-488. ISSN 0583-6050.

For Western Slovenia moderate historical to recent seismicity is characteristic. The principal aim for Slovenia to join the COST 625 project was to exchange the experiences and methodology and in this way to determine the activity or non-activity of selected faults in Western Slovenia. Within the project frame we decided for several years of monitoring, and in this sense four TM 71 extensometers were installed in Western Slovenia. In the first half of the 2004 two TM 71 instruments were installed in Postojnska Jama on the Dinaric oriented fault that is situated about 1 km North from Predjama fault. The third instrument was installed on Raša fault on the SE slope of Vremščica and the fourth instrument in Učja valley on Idrija fault. The fifth instrument TM 71 will be set up on Kneža fault that is situated south from Ravne fault. The first results from Postojnska Jama are showing the small horizontal movements for 0.05 mm in one year.

Petrič, M., Šebela, S. 2005. Hydrogeological research as a basis for the preparation of the plan of monitoring groundwater contamination – A case study of the Stara vas landfill near Postojna (SW Slovenia).

Acta Carsologica, 34 (2), 489-506. ISSN 0583-6050.

For the present 9 landfills on karst are still active in Slovenia, among them also the Stara vas landfill near Postojna. As strong fissuration of the rock base and very good permeability is typical for karst areas, the waste waters from the landfills particularly endanger the groundwater. The capacity of natural filtration in karst is very low and the dimension of possible negative impact is very high. The actual legislation regulates the performance of operational monitoring, a part of which is also the measurement of parameters of contamination of groundwater by hazardous substances, if they are in the area of influence of the landfill. Preparation of the monitoring plan is based on adequate hydrogeological researches. Besides basic geological and hydrogeological data also the results of tracer tests were used in the case study of the Stara vas landfill. Additionally, the detailed tectonic-lithological mapping in the scale 1:5000 was performed in the narrow area of the landfill. Based on defined characteristics of underground water flow and in accordance with the regulations 3 monitoring points inside (Malenščica and Vipava springs, Fužina cave) and one point outside the area of influence of the landfill (Matijeva jama cave) were selected. The monitoring plan for the observation of water quality and capacity was suggested.

Gabrovšek, F. 2005. Caves in conglomerate: Case of Udin boršt, Slovenia.

Acta Carsologica, 34 (2), 507-520. ISSN 0583-6050.

Speleologically, a »pie« of mainly carbonate conglomerate atop of a sequence of impermeable oligocene and mainly fed by autochtonic waters, represent a simple speleological settings. There are 14 registered caves in the area, mostly concentrated along the western rim of the terace. Four caves extend more than 200 m, the cave Arneževa luknja is the longest with 815 m. In the chapter I describe the general speleological settings in Udin boršt, characteristics of caves and factors important for their genesis.

Kranjc, A. 2005. Conglomerate Karst in Slovenia: history of cave knowledge and research of Udin boršt (Gorenjsko).

Acta Carsologica, 34 (2), 521-532. ISSN 0583-6050.

Folk tales and tradition evidence that people in Udin boršt were aware of caves from old. In the 19th century a special type of outlaws occurred in Gorenjska. One of the centres was in Udin boršt where brigands hid in caves. Under the French occupation the villagers hid in the caves, while during the 2nd World War they were partisans. Water is another factor playing an important role at studying Udin boršt. Most of the villages were water supplied from Udin boršt, partly out of caves. As elsewhere in conglomerates in Udin boršt also there are traces of rock cutting for millstones. The first printed news about the caves in Udin boršt are found in Valvasor’s Die Ehre des Herzothums Crain. The book History of the Ljubljana Bishop’s Diocese. The modern caving research started in 1946. In 1954 the members of the Natural Science Circle of the 1st Grammar School, Kranj started to visit caves in Udin boršt. About that time a co:worker of the Karst Research Institute from Postojna started to research these caves. The caves in Udin boršt were revisited in the seventieths of the past century in connection with the project “Speleological Map of Slovenia”. The connection between the people and the land can be seen from the topographical names too. The last part of the paper deals with these names, including the explanation of the name Udin boršt.