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Contents and Abstracts
TAK Reviews
Dreybrodt, W., Gabrovsek, F. & Siemers, J. Dynamics of the evolution of early karst. pp. 9–28.
The evolution of karst conduits due to calcite aggressive water flowing in initially narrow fractures requires a non-linear rate law for limestone dissolution close to equilibrium with respect to calcite. A mathematical analysis of the evolution of limestone dissolution rates of water in such early, narrow fractures as a function of the distance from the input reveals an exponential decrease of the dissolution rates for linear dissolution rate laws (n = 1), such that subsurface karstification is prevented.
For non-linear kinetics (n > 2), however, the decrease of rates proceeds by a hyperbolic relation, such that dissolution rates at the exit of the fracture are still sufficiently high to create a feedback mechanism by which after a long time of gestation a dramatic increase in the widths of the conduits is established. After this breakthrough event, even widening along the entire channel determines the further evolution. The time to achieve breakthrough is given by , where is the initial widening in cm/year at the exit of the conduit. This equation defines the parameters, which determine karstification. The equation above, however, holds only when the calcium concentration of the inflow solution is less than 99% of saturation. Otherwise the positive feedback loop is switched off and the conduit widens evenly along its entire length with rates of 10–9 cm/year to enlarge extremely narrow fractures with initial widths of several ten microns over distances of kilometres to sizes of about 0.1 mm within several ten millions of years. This provides a general explanation for the concept of inception horizons, where usually other mechanisms have been assumed.
The results on one-dimensional conduits were applied to two-dimensional nets of initial fractures. These are constructed on a square-lattice by occupying the lines between nearest neighbour sites by a water conducting fissure of width a0 and length l with an occupation probability p. For p > 0.5 percolating nets occur which carry water. To simulate cave genesis in step 1 we calculate the water flow rates driven by the hydraulic head h through all fissures. Then, in step 2 the one-dimensional transport-dissolution model is applied to each of these fractures and the evolution of their widths is calculated during a time step . Iterating step 1 and step 2 the evolution of the two-dimensional system is modelled. At the onset of karstification flow is evenly distributed on all fractures. As the system develops solutional widening creates preferred pathways, which attract the flow more and more, until at breakthrough both widening and flow increase dramatically. A numerical analysis of breakthrough times in dependence on the parameters a0 (width of the initial fractures), L (horizontal dimension of the aquifer), h (hydraulic head acting on it), and on the chemical parameters of the dissolution kinetics reveals that the relation valid for one-dimensional conduits is also valid for two dimensional ones. The consequences of the dependence of breakthrough time on the various parameters determining karstification are finally discussed.
TAK Articles
Martin, P. Dynamique non linéaire et fonctionnement hydrodynamique de l’endokarst du massif de la Sainte Baume (Bouches du Rhône, Var, France). pp. 29–44.
L’étude des systèmes karstiques a été conduite jusqu’à maintenant soit en travaillant sur des parties de l’hydrogramme, soit en traitant par des analyses corrélatoire et spectrale simples et croisées les chroniques de pluies et de débits. Les pluies étant considérées comme un signal aléatoire que filtre le système karstique.
Nous nous proposons d’utiliser dans l’analyse du fonctionnement des hydro-systèmes karstiques les outils de ce que l’on nomme la dynamique non linéaire. Nous avons donc calculé, sur quatre systèmes karstiques du massif de la Sainte Baume, la dimension de capacité, la dimension de corrélation et le plus important exposant de Lyapunov. Les attracteurs ont ensuite été représentés dans l’espace des phases.
Dans tous les cas, les chroniques de débits préalablement stationnarisées ne correspondent pas à un bruit blanc. On observe par contre une stabilisation de la dimension de corrélation, plus significative car les chroniques sont relativement courtes, pour des valeurs comprises entre 2,5, dans le cas de système très karstfié, et 3,2 dans le cas de système peu karstifié. Les exposants de Lyapunov sont toujours supérieurs à zéro.
Dans l’espace des phases les attracteurs sont très dissemblables. Celui du système karstifié ressemble à une « pointe de flèche ». Celui du système peu karstifié à une « pelote de ficelle très lache ». Ayant randonisé ces deux chroniques, on vérifie que les attracteurs révélés ne correspondent pas à celui d’un bruit blanc. Il semble donc bien que nous soyons en présence d’attracteurs étranges de dimension fractale voisine de 3.
Vasileva, D. & Komatina, K., A. contribution to the alpha recession coefficient investigation in karst terrains. pp. 45–54.
Due to its discontinuous, inhomogeneous structure, specific features and uneven physico-chemical processes developed in different directions, karst offers a very complex environment in terms of qualitative and quantitative treatment of the water bearing parameters. Variable discharge springs with pronounced variations over the time interval of a year prevail in the Dinaric karst. Minimum spring discharges are for the most part recorded during the November–March interval, and maximum discharges in August–October.
The analysis of the recession curve is very important for the investigation of the groundwater regime and resources. The a recession coefficient is obtained from either spring flow rate data, or groundwater level data, during draught periods.
Our investigations have been performed over the Central Dinaric karst terrains. The present paper presents the computation method, as well as recession coefficient values obtained in a multitude of actual cases.
The a recession coefficient is a very important parameter, especially for the karst terrains, so its derivation, as well as its utilization should be treated seriously, especially in water balance computations and in recession curve analysis. It is necessary to emphasize that this parameter has not been sufficiently used in practice and it had to be considered in further investigations.
Vasileva, D. Large springs in the karst of Yugoslavia. pp. 55–62.
Large springs (minimum yields Qmin>50 l/s) in the karst of Yugoslavia are discussed in the present paper. They occur at the contact of carbonate rocks with low permeability rocks.
The south-western extremity of Yugoslavia is for the most part covered by a thick complex of carbonate rocks which form terrains of a definite geomorphology, belonging to holokarst. Characteristic to the large springs in these terrains (especially in the Coastal Karst Belt) are their large flow rate fluctuations over a year time span.
The western and eastern parts of Yugoslavia are covered by carbonate rocks of smaller thickness, partially overlain with vegetation. They have weakly developed karst geomorphology and belong to the merokarst. The flow rate fluctuations of the large springs are less important.
The overall discharge of the large springs could amount to Qmin=22m3/s, which has been ascertained as a reliable, high quality resource (drinking water). This resource is available over the entire period of a year, being able to supply 1/3 of the total water demand for population and industry. There is also another interest related to large springs: they become more and more a tourist attraction in arid karst regions.
Tenu, A., Davidescu, F., Echinger, L. & Voerkelius, S. Quality evaluation of groundwaters in Southern Dobrogea (Romania). pp. 63–78.
In Southern Dobrogea there are two major aquifers the economic interest of which derives from the area extension of the reservoir (over 5,000 sq. km) and the potential flow rates.
The Lower aquifer is located in the Jurassic and Barremian limestone formations, sometime fractured and karstified; in the most part of the region it represents a unitary complex.
The Upper aquifer is significant from the hydrogeological standpoint in the south-eastern part of the region where the thickness of the Sarmatian limestone deposits exceeds 10 m.
Beginning with 1993 a regional monitoring system for qualitative parameters has been initiated. The results were obtained during a three years time Romanian-German cooperation. Based on more than 1,500 determinations, some remarks were made concerning spatial hydrochemical features and hydrochemical facies changes. The regional situation from the point of view of some pollution indicators, the toxic compounds and the NO3– isotopes was also presented.
Two main conclusions concerning the pollution aspects in the region can be mentioned.
The Barremian-Jurassic (Lower) aquifer may be appreciated as having waters of exceptional quality at this moment. The groups of organo-chlorinated pesticides, toxic compounds, triazinic herbicides and halogenated hydrocarbons are completely missing from the whole aquifer; the presence of the two compounds with concentrations below the admissible standard limits may be considered accidental and strictly local. NO3- by the found contents and especially by the pattern of the regional distribution suggests the existence of a diffuse pollution, an incipient phenomenon - possibly fluctuating - which requires a careful regional survey. NH4+ found in some boreholes in quantities over 0.5 mg/l shows accidental pollutions which can be rapidly solved by local measures.
The Sarmatian (Upper) aquifer may be appreciated as having a dispersed pollution in about 25–30% of the sampled points. This occurs as exceeded contents of NH4+ and NO3– ; from the toxic compounds, especially the herbicides group is present.
Stevanovic, Z., Dokmanovic, P. & Jemcov, I. Several highly productive wells in karst areas of Eastern Serbia (Yugoslavia). pp. 79–86.
The hydrogeological investigations of the southeastern part of the Kucaj Mt. karst aquifer performed from 1992 to 1996 for the regional water supply system “Bogovina” (“transitional solution”), included drilling and pumping tests of several wells. Results for three (IE-2, IE-3, IE-4) out of six wells confirmed the expected well yields (50-150 l/s) of high quality ground water and supported the designed water supply concept for the Timok region (Eastern Serbia).
Afrasiabian, A. Karst water budget study in Maharlu karst basin (SW Iran). pp. 87–92.
The study of karst water resources and potential has a particular importance, in semi-arid zones of Iran where there is a great need for discovering new potable water resources.
The study area is located in SW of Iran, with a surface of 4200 sq. km and includes the city of Shiraz and its surroundings. The water budget study, extended over three years, shows that there is a great karst water potential in the area. The volume of karst groundwater is calculated to be of 19mc/s under normal climatic conditions.
Diaconu, G. Le karst: un système de sédimentation continental. pp. 93–104.
Conformément à White et al. (1995), la surface continentale occupée par le karst est d’environ 20%. En dépit de ce fait et des nombreux travaux d’une réelle importance concernant la sédimentologie des zones karstiques, on constate que les traités de pétrographie sédimentaire, les ignore; ils se résument à la simple invocation des spéléothèmes (et seulement de ceux carbonatés) ou bien de certains dépôts de phosphorites (guano) du domaine spéléan.
Pour ces raisons l’auteur considère le karst comme un système de sédimentation continental dans lequel il distingue deux sous-systèmes de sédimentation: le sous-système exokarstique et le sous-système endokarstique. Pour chacun d’entre eux sont présentées les zones caractéristiques avec les types des sédiments spécifiques.
Guendon, J., L., Bruxelles, L., Magnin, F. & Quinif, Y. Sédiments carbonatés karstiques: travertins et spéléothèmes. Évolutions paléoenvironnementales et paléogéographiques; paléosismo-tectonique; exemples dans le Sud de la France. pp. 105–114.
Les spéléothèmes et les travertins des régions calcaires sont des formations sédimentaires carbonatées corrélatives des dissolutions karstiques. Ces dépôts chimiques sont donc à l'image du fonctionnement et de l'évolution des systèmes karstiques et de leurs contextes environnementaux. Ces formations peuvent préserver également des restes floristiques ou faunistiques témoins des conditions bioclimatiques passées ou enregistrer, au cours de leur développement, des anomalies mécaniques résultant de mouvements du substratum. Datables par plusieurs méthodes physico-chimiques, ces sédiments constituent ainsi des archives sur l'évolution des systèmes karstiques, sur les changements paléogéographiques et paléoenvironnementaux ou sur des événements sismo-tectoniques régionaux.
Ghergari, L., Tamas, T., Damm, P. & Forray, F. Hydrothermal paleokarst in Pestera din Valea Rea (Bihor Mountains, Romania). pp. 115–126.
The paper presents two hydrothermal veins from Pestera din Valea Rea, found at the depth of –115 m on the cave's active passage. They have a columnar shape and oval section, with diameters between 30 and 50 cm and resulted by the filling of channels formed in hydrothermal karst conditions. Our studies (binoculary microscopy, transmission and reflection polarizing microscopy, transmission electron microscopy, X-ray diffractometry, IR absorption spectroscopy and thermal analyses) were focused on the structures and textures of the hydrothermal fillings, as well as on the mineralogical association: quartz, calcite, dolomite, barite, dickite, smectite/dioctahedral chlorite, illite/montmorillonite, montmorillonite, gold and pyrite almost integrally transformed in goethite and lepidocrocite. The order of crystallization was: colorless quartz I ± pyrite ± carbonates — grey quartz ± gold — quartz II, dickite — smectitic minerals. The paragenesis is epithermal and was caused by microgranitic dykes from the vicinity of the cave.
Silvestru, E. Dolines in the Padis Plateau (Bihor Mountains, Romania) — One peculiar case, many questions. pp. 127–132.
Dolines are much of an archetype of karst relief reason for which less and less karstologists approach them as self-standing research entities. Following a flourishing research period of dolines in the forties and fifties, they were shifted into larger research contexts, especially karst denudation. Dolines formed in karst cover underwent a long terminological odyssey, resulting in a quite elaborate classification.
Based on the exceptional density of this particular type of doline in the Padi¿ Plateau (Bihor Mountains, Romania) we first attempt a simplification of terminology, by proposing a new general category - slumping doline — and re-assessing an older category — suffosion doline. A brief presentation of the perimeter follows, as one of the most densely doline-populated in Romania and probably in Europe, as well as the one with the thickest cover (up to 85 m) in Romania. We end by proposing the concept of “para-karstic aquifer”.
Vremir, M. & Tamas, T. Large holocene mammals from “Pestera cu Ceata” Cave (Bihor Mountains, Romania). pp. 133–141.
During the exploration of Pestera cu Ceata cave from the Upper Basin of Some¿ul Cald river, an important deposit of fossil remains of large mammals of Holocene age was discovered. These bones belong to an Ursus arctos, to a Bos primigenius male, to ten Cervus elaphus males of at least three generations (most of them young), and to a Capreolus capreolus female, the latter of more recent age. So far, more than 250 pieces were inventoried between October 1996 and March 1997. Their description, with a series of biometric measurements included, is completed with statistic, taphonomic and palaeoenvironmental observations.
Petculescu A. & Radulescu, C. Late pleistocene small mammals from Pestera Vacilor (Mehedinti Plateau, Romania). pp. 141–152.
An association of small mammals containing 20 species (4 insectivores, 15 rodents and one ochotonid lagomorph) has been recovered from karst deposits at Pestera Vacilor (Cows' Cave) (Mehedinti Plateau, southwestern Romania). Cricetulus migratorius, Mesocricetus newtoni, Cricetus cricetus and Ochotona pusilla represent allochtonous steppe elements occurring at Vacilor Cave outside their present area of distribution. As a whole, the fauna consists predominantly of species of open environment (Spermophilus, Cricetulus, Cricetus, Mesocricetus, Sicista subtilis, Microtus arvalis, Ochotona) and rocky ground (Chionomys nivalis), in association with woodland forms (Myoxus glis, Dryomys, Muscardinus, Apodemus sylvaticus, A. flavicollis, Clethrionomys glareolus) present in a relatively low frequency. The small mammal association from Vacilor Cave is considered to correspond to a climatic shift from warmer to cooler, more continental conditions. This transitional climatic phase may be assigned, on the basis of the general evolutionary stage of the fauna and of the stratigraphic significance of Mesocricetus newtoni (known in southwestern Romania only during the Early Würm), to the first half of the last glacial cycle (Würm/Vistula).
Radulescu, A., Codrea, V. & Petculescu, A. Middle Pleistocene small-sized Pliomys of Romania. pp. 153–160.
On the basis of dental material coming from two Middle Pleistocene sites (Subpiatra Quarry near Alesd, Bihor County and Rotbav-Dealul Tiganilor near Brasov, Brasov County), a new species, Pliomys samsoni n. sp. (Pliomyini, Arvicolidae, Rodentia, Mammalia) is described. In both sites, P. samsoni n. sp. is associated with primitive Arvicola forms. Chronostratigraphic data suggest that fossiliferous deposits containing P. samsoni n. sp. may be assigned to the Middle Pleistocene (end of the Cromerian marked by the first appearance of Arvicola in Europe).
Iurkiewicz, A. & Feru, A. — Karst and non-karst occurrences of natural mineral still waters. pp. 161–166.
Based on the main physico-chemical parameters one perform a comparative analysis of the still natural mineral waters originating in karst and non-karst areas. To this purpose, there have been chosen three mineral water sources in Romania, together with other important sources in Europe, with similar mineral water.
Povara, I., Horoi, V., Marin, C., Nicolescu, T. & Baciu, M. Investigations on the covered saline karst in Slanic Prahova area (Romania). pp. 167–176.
The mechanical disequilibria due to the mining works undertaken in Slånic-Prahova area have determined the occurrence within the salt massif of a network of fissures that favored surface water infiltrations. The infiltration paths had a rapid evolution concentrating in well-organized drains the water accumulated within the Badenian deposits (siltic clays and marls) that cover the salt massif. The detailed morphological analysis of the massif and the monitoring of the flows, temperatures and chemistry of the infiltrations allowed the establishment of the water sources and the preferential flow directions, offering therefore the necessary elements for reducing the hydrogeologic risk.
Short Notes
Sarin, A., Kranjc, A., Kapelj, S., Kogovsek, J. & Buljan, R. On the significance of dissolved carbonates in karst processes (Gams’ approach) — a call for research cooperation. pp. 177–180.
Petculescu, A. On the presence of Mimomys intermedius (Newton, 1881) (Arvicolide, Rodentia, Mammalia) in the Tecuri Cave (Hundeoara County, Romania). pp. 181–184.
In Memoriam
Valer Trufas (1931–1997). pp. 185–186.