MWH Global

Enviroscan Ukrainian Institute of Speleology and Karstology

Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 5
Community news

Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

Did you know?

That pisolite, pisolith is see cave pearl.?

Checkout all 2699 terms in the KarstBase Glossary of Karst and Cave Terms

Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 7
What is Karstbase?



Browse Speleogenesis Issues:

KarstBase a bibliography database in karst and cave science.

Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
See all featured articles
Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
See all featured articles from other geoscience journals

Search in KarstBase

Your search for stress (Keyword) returned 119 results for the whole karstbase:
Showing 106 to 119 of 119
Effects of dynamically variable saturation and matrix-conduit coupling of flow in karst aquifers, 2011,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Reimann T. , Geyer T. , Shoemaker W. B. , Liedl R. , Sauter M.

Well-developed karst aquifers consist of highly conductive conduits and a relatively  low permeability fractured and/or porous rock matrix and therefore behave as a dualhydraulic  system. Groundwater flow within highly permeable strata is rapid and transient  and depends on local flow conditions, i.e., pressurized or nonpressurized flow. The  characterization of karst aquifers is a necessary and challenging task because information  about hydraulic and spatial conduit properties is poorly defined or unknown. To investigate  karst aquifers, hydraulic stresses such as large recharge events can be simulated with hybrid  (coupled discrete continuum) models. Since existing hybrid models are simplifications of  the system dynamics, a new karst model (ModBraC) is presented that accounts for unsteady  and nonuniform discrete flow in variably saturated conduits employing the Saint-Venant  equations. Model performance tests indicate that ModBraC is able to simulate (1) unsteady  and nonuniform flow in variably filled conduits, (2) draining and refilling of conduits with  stable transition between free-surface and pressurized flow and correct storage  representation, (3) water exchange between matrix and variably filled conduits, and (4)  discharge routing through branched and intermeshed conduit networks. Subsequently,  ModBraC is applied to an idealized catchment to investigate the significance of free-surface  flow representation. A parameter study is conducted with two different initial conditions:  (1) pressurized flow and (2) free-surface flow. If free-surface flow prevails, the systems is  characterized by (1) a time lag for signal transmission, (2) a typical spring discharge pattern  representing the transition from pressurized to free-surface flow, and (3) a reduced conduitmatrix  interaction during free-surface flow.

Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
White, Elizabeth L.

Collapse of cave passages results in piles of fallen rock fragments known as breakdown. Breakdown occurs as blocks, slabs, and chips, as isolated rock fragments, and as massive piles of fallen rock. Models for the formation of breakdown include brittle fracture under gravitational loading of fixed or cantilever beams and also by microfracturing with inelastic creep. Geological mechanisms that trigger breakdown include loss of buoyant support, dissolutional action of vadose waters, frost pry, and mineral replacement. Breakdown plays an important role in the final stages of the truncation and decay of caves as surface erosion destroys the system.

Deep hydrogeology: a discussion of issues and research needs, 2013,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Tsang Chinfu, Niemi Auli

In this essay, “deep hydrogeology” is somewhat arbitrarily defined as hydrogeology in the subsurface deeper than 1 km, below which the effect of residual permeability at high stresses becomes evident (Neuzil 2003; Rutqvist and Stephansson 2003; Liu et al. 2009). Studies have shown that meteoric fluids are present in the earth’s crust from land surface to at least a depth of 10–15 km (Kozlowsky 1987; Taylor Jr 1990; Zharikov et al. 2003; Ge et al. 2003). At such depths, interaction with surface water and surface events over time periods of 100 or 1,000 years may be minimal, except in areas of very deep mining activities or where deep convection is enhanced by active magmatism. Deep drilling to several kilometers in depth is often done for petroleum and geothermal reservoir exploration and exploitation. The focus of such activities is reservoir identification, capacity evaluation, and fluid and heat extractability. However, it is largely an open area of research to understand the state, structure and evolution of deep hydrogeology over time scales of tens of thousands of years or more, especially in areas lacking petroleum and geothermal resources. Interest in attaining such an understanding has emerged from the need for long-term predictions related to nuclear waste disposal and from recognition of the role that hydrogeology may play in seismicity, orogenesis and various geological processes, as well as in global fluid and chemical cycles. A number of wide-ranging questions may be asked regarding deep hydrogeology, several of which are as follows: What are the current and past states of fluid pressure, temperature and chemical composition in deep formations? How does fluid transport mass and heat? What are the fluid sources and driving mechanisms? What are the magnitude and distribution of porosity and permeability? What are the occurrence and characteristics of large-scale flow, including thermally and chemically driven convection systems? What is the nature of local anomalous fluid pressures and what are their implications? The purpose of this essay is to discuss key issues and research needs in deep hydrogeology. It is based on a workshop on the subject held at Uppsala University in Sweden, with participants from 11 countries, including the USA, Russia, Japan and a number of European countries (Tsang et al. 2012). The following discussion will be divided into sections on permeability structures, driving forces, coupled processes, borehole testing and data analysis, followed by a few concluding remarks.

Early results of micro-deformation measurements in Magdalena Jama (Slovenia) by a vertical static pendulum, 2013,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Kalenda Pavel, Neumann Libor, Šebela Stanka

Vertical static pendulums have been installed in mines or caves in Central Europe since 2007. Two­dimensional optical measurement of the tilt of a rock mass and continuous fully digital on­line evaluation of results makes possible the detection of a small tilt of the surroundings with a resolution of tens of nanoradians or the deformation of the surroundings in the horizontal plane with resolution of hundreds of nanometres. The paper describes the measurement device and the first results of the measurements in Magdalena Jama, which is part of the Postojna Cave System (Slovenia). The correlation of deformation between distant stations shows the existence of stress variations that are not only of local origin (high floods, local seismicity, and aseismic deformations). The stress field has a wider, and not only regional, character with effects that can be observed very far from the origin.

Physical Structure of the Epikarst, 2013,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Jones, William K.

Epikarst is a weathered zone of enhanced porosity on or near the surface or at the soil/bedrock contact of many karst landscapes. The epikarst is essentially the upper boundary of a karst system but is also a reaction chamber where many organics accumulate and react with the percolating water. The epikarst stores and directs percolating recharge waters to the underlying karst aquifers. Epikarst permeability decreases with depth below the surface. The epikarst may function as a perched aquifer with a saturated zone that transmits water laterally for some distance until it drains slowly through fractures or rapidly at shaft drains or dolines. Stress-release and physical weathering as well as chemical dissolution play a role in epikarst development. Epikarst may be found on freshly exposed carbonates although epikarst that develops below a soil cover should form at a faster rate due to increased carbon dioxide produced by vegetation. The accumulation of soil within the fractures may create plugs that retard the downward movement of percolating water and creates a reservoir rich in organic material. The thickness of the epikarst zone typically ranges from a few meters to 15 meters, but vertical weathering of joints may be much deeper and lead to a “stone forest” type of landscape. Some dolines are hydrologically connected directly to the epikarst while other dolines may drain more directly to the deeper conduit aquifer and represent a “hole” in the epikarst. water stored in the epikarst may be lost to evapotranspiration, move rapidly down vertical shafts or larger joints, or drain out slowly through the soil infillings and small fractures. Much of the water pushed from the epikarst during storms is older water from storage that is displaced by the new event water.

‘Looping caves’ versus ‘water table caves’: The role of base-level changes and recharge variations in cave development, 2014,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Gabrovšek Franci, Häuselmann Philipp, Audra Philippe

The vertical organisation of karst conduit networks has been the focus of speleogenetic studies for more than a century. The four state model of Ford and Ewers (1978), which still is considered as the most general, relates the geometry of caves to the frequency of permeable fissures. The model suggests that the ‘water table caves’ are common in areas with high fissure frequency, which is often the case in natural settings. However, in Alpine karst systems, water table caves aremore the exception than the rule. Alpine speleogenesis is influenced by high uplift, valley incision rates and irregular recharge. To study the potential role of these processes for speleogenesis in the dimensions of length and depth, we apply a simple mathematical model based on coupling of flow, dissolution and transport.We assume a master conduit draining thewater to the spring at a base level. Incision of the valley triggers evolution of deeper flow pathways,which are initially in a proto-conduit state. Themaster conduit evolves into a canyon following the valley incision,while the deep pathways evolve towards maturity and tend to capture the water fromthe master conduits. Two outcomes are possible: a) deep pathways evolve fast enough to capture all the recharge, leaving the master conduit dry; or b) the canyon reaches the level of deep pathways before these evolve to maturity. We introduce the Loop-to-Canyon Ratio (LCR), which predicts which of the two outcomes is more likely to occur in certain settings. Our model is extended to account for transient flow conditions. In the case of an undulating master conduit, floodwater is stored in troughs after the flood retreat. This water seeps through sub-vertical fractures (‘soutirages’) connecting the master conduitwith the deep pathways. Therefore, the loops evolve also during the dry season, and the LCR is considerably increased. Although themodel is based on several approximations, it leads to some important conclusions for vertical organisation of karst conduit networks and stresses the importance of base-level changes and transient recharge conditions. It therefore gives an explanation of speleogenesis that relies much more on the dynamic nature of water flow than on the static fracture density

Characteristics of gas disaster in the Huaibei coalfield and its control and development technologies, 2014,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Wang L. , Cheng Y. , An F, Zhou H. , Kong S. , Wang W.

The Huaibei coalfield is in the East China Economic Area, which is rich in coal and gas resources. However, hundreds of coal and gas outburst accidents have occurred because of the complex geological structures of the coalfield. Based on theoretical analysis and field statistics, the characteristics of regional geological structures and the coal measure strata evolution in the Huaibei coalfield were researched, and gas resource distribution and gas parameters were statistically analyzed to determine the dominant controlling factors of gas occurrence and gas dynamic disaster. The results indicated that the Huaibei coalfield has undergone complex tectonic evolution, causing obvious differences in gas storage in different blocks of different mining areas, which exhibits a pattern of high amounts of gas in the south and east, and low amounts of gas in the north and west. The coal seam and gas occurrence have a bipolar distribution in the coalfield caused by multiple tectonic movements, and they are deeply buried. Horizontal tectonic stress plays a dominant role in gas outburst, and the thermal evolution and trap effects of magma intrusion increase the possibility and extent of gas outburst. Considering coal seam and gas occurrence characteristics in the coalfield, we propose a new technology for deep coal reservoir reconstruction which combined present underground regional gas control methods and surface well extraction methods. The technology has three effects: developing gas resources, improving coal mining safety level and reducing greenhouse gas emissions, which has been practiced to be effective in coal mines in the Huaibei coalfield.

Deep conduit flow in karst aquifers revisited, 2014,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Kaufmann Georg, Gabrovšek Franci, Romanov Douchko

Caves formed in soluble rocks such as limestone, anhydrite, or gypsum are efficient drainage paths for water moving through the aquifer from the surface of the host rock towards a resurgence. The formation of caves is controlled by the physical solution through dissociation of the host rock by water or by the chemical solution through reactions of the host rock with water enriched with carbon dioxide. Caves as large underground voids are simply the end member of secondary porosity and conductivity characterizing the aquifer.

Caves and their relation to a present or past base level are found both close to a past or present water table (water-table caves) and extending far below a past or present water table (bathy-phreatic caves). One explanation for this different speleogenetic evolution is the structural control: Fractures and bedding partings are preferentially enlarged around more prominent faults, thus the fracture density in the host rock controls the speleogenetic evolution. This widely accepted explanation [e.g. Ford and Ewers, 1978] can be extended by adding other controls, e.g. a hydraulic control: As temperature generally increases with depth, density and viscosity of water change, and particularly the reduction of viscosity due to the increase in temperature enhances flow. This hypothesis was proposed by Worthington [2001, 2004] as a major controlling factor for the evolution of deep-bathyphreatic caves.

We compare the efficiency of structural and hydraulic control on the evolution of a cave passage by numerical means, adding a third control, the chemical control to address the change in solubility of the circulating water with depth. Our results show that the increase in flow through deep bathy-phreatic passages due to the decrease in viscosity is by far outweighted by effects such as the decrease in fracture width with depth due to lithostatic stress and the decrease in solubility with depth. Hence, the existence of deep bathy-phreatic cave passages is more likely to be controlled by the structural effect of prominent faults.

The use of damaged speleothems and in situ fault displacement monitoring to characterise active tectonic structures: an example from Zapadni Cave, Czech Republic , 2014,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Briestensky Milos, Stemberk Josef, Rowberry Matt D. ,

The EU-TecNet fault displacement monitoring network records three-dimensional displacements across specifically selected tectonic structures within the crystalline basement of central Europe. This paper presents a study of recent and active tectonics at Západní Cave in northern Bohemia (Czech Republic). It extends previous geological research by measuring speleothem damage in the cave and monitoring displacements across two fault structures situated within the Lusatian Thrust Zone. The speleothem damage reflects strike-slip displacement trends: the WSW-ENE striking fault is associated with dextral strike-slip displacement while the NNW-SSE striking fault is associated with sinistral strike-slip displacement. These measurements demonstrate that the compressive stress σ1 is located in the NW or SE quadrant while the tensile stress σ3 is oriented perpendicular to σ1, i.e. in the NE or SW quadrant. The in situ fault displacement monitoring has confirmed that movements along the WSW-ENE striking fault reflect dextral strike-slip while movements along the NNW-SSE striking fault reflect sinistral strike-slip. In addition, however, monitoring across the NNW-SSE striking fault has demonstrated relative vertical uplift of the eastern block and, therefore, this fault is characterised by oblique movement trends. The fault displacement monitoring has also shown notable periods of increased geodynamic activity, referred to as pressure pulses, in 2008, 2010-2011, and 2012. The fact that the measured speleothem damage and the results of fault displacement monitoring correspond closely confirms the notion that, at this site, the compressive stress σ1 persists in the NW or SE quadrant. The presented results offer an insight into the periodicity of pressure pulses, demonstrate the need for protracted monitoring periods in order to better understanding geodynamic processes, and show that it is possible to characterise the displacements that occur across individual faults in a way that cannot be accomplished from geodetic measurements obtained by Global Navigation Satellite Systems.

Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943

Tectonic research and morphologi calobservations were carried out in six caves (Kalacka, Goryczkowa, Kasprowa Ni¿na, Kasprowa OErednia, Kasprowa Wy¿nia and Magurska) in the Bystra Val ley, in the Tatra Moun -tains. There are three cave lev els, with the youn gest ac tive and the other two in ac tive, re flect ing de vel op ment partly un der epiphreatic and partly un der phreatic con di tions. These stud ies dem on strate strong con trol of the cave pat tern by tec tonic fea tures, in clud ing faults and re lated frac tures that orig i nated or were re ju ve nated dur ing up lift,last ing from the Late Mio cene. In a few lo cal cases, the cave pas sages are guided by the com bined in flu ence of bed ding, joints and frac tures in the hinge zone of a chev ron anticline. That these cave pas sages are guided by tec tonic struc tures, ir re spec tive of lithological dif fer ences, in di cates that these proto-con duits were formed by “tec tonic in cep tion”. Dif fer ences in the cave pat tern be tween the phreatic and epiphreatic zones at a given cave level may be a re sult of mas sif re lax ation. Be low the bot tom of the val ley, the ef fect of stress on the rock mass is re lated to the re gional stress field and only in di vid ual faults ex tend be low the bot tom of the val ley. Thus in the phreatic zone, the flow is fo cused and a sin gle con duit be comes en larged. The lo cal ex ten sion is more in tense in the epiphreatic zone above the val ley floor and more frac tures have been suf fi ciently ex tended to al low wa ter to flow. The wa ter mi grates along a net work of fis sures and a maze could be form ing. Neotectonic dis place ments (of up to 15 cm), which are more re cent than the pas sages, were also iden ti fied in the caves. Neotectonic ac tiv ity is no lon ger be lieved to have as great an im pact on cave mor phol ogy as pre vi ously was thought. Those faults with dis place ments of sev eral metres, de scribed as youn ger than the cave by other au thors, should be re clas si fied as older faults, the sur faces of which have been ex posed by speleogenesis. The pos si ble pres ence of neotectonic faults with greater dis place ments is not ex cluded, but they would have had a much greater mor pho log i cal im pact than the ob served fea tures sug gest.

Tectonic control of cave development: a case study of the Bystra Valley in the Tatra Mts., 2015,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Szczygieł Jacek, Gaidzik Krzysztof, Kicińska Ditta

Tectonic research and morphological observations were carried out in six caves (Kalacka, Goryczkowa, Kasprowa Niżna, Kasprowa Średnia, Kasprowa Wyżnia and Magurska) in the Bystra Valley, in the Tatra Mountains. There are three cave levels, with the youngest active and the other two inactive, reflecting development partly under epiphreatic and partly under phreatic conditions. These studies demonstrate strong control of the cave pattern by tectonic features, including faults and related fractures that originated or were rejuvenated during uplift, lasting from the Late Miocene. In a few local cases, the cave passages are guided by the combined influence of bedding, joints and fractures in the hinge zone of a chevron anticline. That these cave passages are guided by tectonic structures, irrespective of lithological differences, indicates that these proto-conduits were formed by "tectonic inception”. Differences in the cave pattern between the phreatic and epiphreatic zones at a given cave level may be a result of massif relaxation. Below the bottom of the valley, the effect of stress on the rock mass is related to the regional stress field and only individual faults extend below the bottom of the valley. Thus in the phreatic zone, the flow is focused and a single conduit becomes enlarged. The local extension is more intense in the epiphreatic zone above the valley floor and more fractures have been sufficiently extended to allow water to flow. The water migrates along a network of fissures and a maze could be forming. Neotectonic displacements (of up to 15 cm), which are more recent than the passages, were also identified in the caves. Neotectonic activity is no longer believed to have as great an impact on cave morphology as previously was thought. Those faults with displacements of several metres, described as younger than the cave by other authors, should be reclassified as older faults, the surfaces of which have been exposed by speleogenesis. The possible presence of neotectonic faults with greater displacements is not excluded, but they would have had a much greater morphological impact than the observed features suggest.

On the applicability of geomechanical models for carbonate rock masses interested by karst processes, 2015,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943

Rock mass classification and geomechanical models have a particular importance for carbonate rocks, due to their peculiar fabric, variability of the main features, and scarce availability of experimental data. Carbonates are particularly sensitive to syn-depositional and post-depositional diagenesis, including dissolution and karstification processes, cementation, recrystallisation, dolomitisation and replacement by other minerals. At the same time, as most of sedimentary rocks, they are typically stratified, laminated, folded, faulted and fractured. The strength and deformability of carbonate rock masses are, therefore, significantly affected by the discontinuities, as well as by their pattern and orientation with respect to the in situ stresses. Further, discontinuities generally cause a distribution of stresses in the rock mass remarkably different from those determined by the classical elastic or elasto-plastic theories for homogeneous continua. Goal of this work is the description of the difficulties in elaborating geomechanical models to depict the stress–strain behavior of karstified carbonate rock masses. Due to such difficulties, a high degree of uncertainty is also present in the selection of the most proper approach, the discontinuum one or the equivalent continuum, and in the numerical model to be used within a specific engineering application as well. The high uncertainty might cause wrong assessments as concerns the geological hazards, the design costs, and the most proper remediation works. Even though recent developments in the application of numerical modeling methods allow to simulate quite well several types of jointed rock masses, as concerns carbonate rock masses many problems in representing their complex geometry in the simulation models still remain, due to peculiarity of the structural elements, and the presence of karst features. In the common practice, the improper use of the geomechanical models comes from a superficial geological study, or from the lack of reliable geological and structural data that, as a consequence, bring to erroneous evaluations of the influence of the geological-structural features on the in situ stress state and the stress–strain rock mass behavior.

The influence of light attenuation on the biogeomorphology of a marine karst cave: A case study of Puerto Princesa Underground River, Palawan, the Philippines, 2015,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Coombes Martin A. , La Marca Emanuela C. , Naylor Larissa A. , Piccini Leonardo, De Waele Jo, Sauro Francesco

Karst caves are unique biogeomorphological systems. Cave walls offer habitat for microorganisms which in-turn have a geomorphological role via their involvement in rock weathering, erosion and mineralisation. The attenuation of light with distance into caves is known to affect ecology, but the implications of this for biogeomorphological processes and forms have seldom been examined. Here we describe a semi-quantitative microscopy study comparing the extent, structure, and thickness of biocover and depth of endolithic penetration for samples of rock from the Puerto Princesa Underground River system in Palawan, the Philippines, which is a natural UNESCO World Heritage Site.

Organic growth at the entrance of the cave was abundant (100% occurrence) and complex, dominated by phototrophic organisms (green microalgae, diatoms, cyanobacteria, mosses and lichens). Thickness of this layer was 0.28 ± 0.18 mm with active endolith penetration into the limestone (mean depth = 0.13 ± 0.03 mm). In contrast, phototrophs were rare 50 m into the cave and biofilm cover was significantly thinner (0.01 ± 0.01 mm, p b 0.000) and spatially patchy (33% occurrence). Endolithic penetration here was also shallower (b0.01mm, p b 0.000) and non-uniform. Biofilm was found 250 m into the cave, but with a complete absence of phototrophs and no evidence of endolithic bioerosion.

We attribute these findings to light-induced stress gradients, showing that the influence of light on phototroph abundance has knock-on consequences for the development of limestone morphological features. In marine caves this includes notches, which were most well-developed at the sheltered cave entrance of our study site, and for which variability in formation rates between locations is currently poorly understood.

Quaternary faulting in the Tatra Mountains, evidence from cave morphology and fault-slip analysis, 2015,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Szczygieł Jacek

Tectonically deformed cave passages in the Tatra Mts (Central Western Carpathians) indicate some fault activity during the Quaternary. Displacements occur in the youngest passages of the caves indicating (based on previous U-series dating of speleothems) an Eemian or younger age for those faults, and so one tectonic stage. On the basis of stress analysis and geomorphological observations, two different mechanisms are proposed as responsible for the development of these displacements. The first mechanism concerns faults that are located above the valley bottom and at a short distance from the surface, with fault planes oriented sub-parallel to the slopes. The radial, horizontal extension and vertical σ1 which is identical with gravity, indicate that these faults are the result of gravity sliding probably caused by relaxation after incision of valleys, and not directly from tectonic activity. The second mechanism is tilting of the Tatra Mts. The faults operated under WNW-ESE oriented extension with σ1 plunging steeply toward the west. Such a stress field led to normal dip-slip or oblique-slip displacements. The faults are located under the valley bottom and/or opposite or oblique to the slopes. The process involved the pre-existing weakest planes in the rock complex: (i) in massive limestone mostly faults and fractures, (ii) in thin-bedded limestone mostly inter-bedding planes. Thin-bedded limestones dipping steeply to the south are of particular interest. Tilting toward the N caused the hanging walls to move under the massif and not toward the valley, proving that the cause of these movements was tectonic activity and not gravity.

Results 106 to 119 of 119
You probably didn't submit anything to search for