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 hydrograph, characteristic is a hydrograph based on the unit step process.?

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

What is Karstbase?

Search KARSTBASE:

keyword
author

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 fault (Keyword) returned 376 results for the whole karstbase:
Showing 346 to 360 of 376
Hypogenic Karstification and Conduit System Controlling by Tectonic Pattern in Foundation Rocks of the Salman Farsi Dam in South-Western Iran, 2013, Koleini Mehran, Van Rooy Jan Louis, Bumby Adam

The Salman Farsi dam project is constructed on the Ghareh Agahaj River about 140km south of Shiraz city in the Zagros Mountains of southwestern Iran. This tectonic province of southwestern Iran is characterized by a simple folded sedimentary sequence. The dam foundation rocks compose of the Asmari Formation of Oligo-miocene and generally comprise of a variety of karstified carbonate rocks varying from strong to weak rocks. Most of the rocks exposed at the dam site show a primary porosity due to incomplete diagenetic recrystallization and compaction. In addition to these primary dispositions to weathering, layering conditions (frequency and orientation of bedding) and the subvertical tectonic discontinuities channeled preferably the infiltrating by deep-sited hydrothermal solutions. Consequently the porosity results to be enlarged by dissolution and the rocks are expected to be karstified and to develop cavities in correspondence of bedding, major joint planes and fault zones. This kind of karsts is named hypogenic karsts which associated to the ascendant warm solutions. Field observations indicate strong karstification and vuggy intercalations especially in the middle part of the Asmari succession. The biggest karst in the dam axis which identified by speleological investigations is Golshany Cave with volume of about 150,000 m3. The tendency of the Asmari limestone for strong dissolution can alert about the seepage from the reservoir and area of the dam locality.


Hydrodynamic modeling of a complex karst-alluvial aquifer: case study of Prijedor Groundwater Source, Republic of Srpska, Bosnia and Herzegovina, 2013, Polomčić Dušan, Dragišić Veselin, Živanović Vladimir

Middle Triassic fractured and karstified limestone and dolomite form a karst aquifer in the Sana River Valley near the town of Prijedor. As a result of intensive tectonic movements, carbonate rocks are mostly below the Sana River level, covered by younger Pliocene and alluvial deposits. The main source of groundwater recharge is infiltration from the Sana River through its alluvium over most of the aquifer. The main objective of the research reported in this paper was to evaluate the hydraulic relationships of the alluvial, Pliocene and karst aquifers in order to better understand the water supply potential of the karst aquifer. Although the use of hydrodynamic modeling is not very common with karst aquifers, the developed model provided significant and useful information on the groundwater budget and recharge type. The influence of fault zones and spatial anisotropy of the karst aquifer were simulated on the hydrodynamic model by varying permeability on the xand y­axes of the Cartesian coordinate system with respect to the fault, the main pathway of groundwater circulation. Representative hydraulic conductivities were Kx

 = 2.3·10­3

 m/s and Ky

 = 5.0·10­3

 m/s in the faults of Nw to SE direction, and Kx

 = 2.5·10­3

 m/s and Ky

 1.2·10­3

 m/s in the faults of Sw to NE trend. Model research showed that the karst aquifer can be used in the long term at maximal tested capacities and that current groundwater exploitation is not compromised in dry periods when the water budget depends entirely on recharge from the Sana River.


Ascending speleogenesis in the Czech Republic and Slovakia , 2013, Bosák P. , Bella P.

Several examples of per ascensum (ascending) speleogenesis along deep faults (cf. also were recently described by Bella & Bosák (2012). The concept of ascending speleogenesis in confined or partly confined conditions connected with deep regional fault was proposed, for the first time on the territory of the past Czechoslovakia, by Bosák (1996, 1997) for the origin of the Koněpruské Caves and some other caves in the Koněprusy Devonian (central Bohemia, Czech Republic). Since that time, number of caves with similar speleogenesis has been studied in more of lesser detail. Most of them were originally described as products of phreatic, epiphreatic and vadose speleogenesis related to the evolution of local water courses, valley incision and river terrace systems usually during Middle to Late Pleistocene climatic changes; eventually with Plio-Quaternary climatic oscillations.


Hypogenic Karstification and Conduit System Controlling by Tectonic Pattern in Foundation Rocks of the Salman Farsi Dam in South-Western Iran, 2013, Koleini M. , Louis J. , Rooy V. , Bumby A.

The Salman Farsi dam project is constructed on the Ghareh Agahaj River about 140km south of Shiraz city in the Zagros Mountains of southwestern Iran. This tectonic province of southwestern Iran is characterized by a simple folded sedimentary sequence. The dam foundation rocks compose of the Asmari Formation of Oligo-miocene and generally comprise of a variety of karstified carbonate rocks varying from strong to weak rocks. Most of the rocks exposed at the dam site show a primary porosity due to incomplete diagenetic recrystallization and compaction. In addition to these primary dispositions to weathering, layering conditions (frequency and orientation of bedding) and the subvertical tectonic discontinuities channeled preferably the infiltrating by deep-sited hydrothermal solutions. Consequently the porosity results to be enlarged by dissolution and the rocks are expected to be karstified and to develop cavities in correspondence of bedding, major joint planes and fault zones. This kind of karsts is named hypogenic karsts which associated to the ascendant warm solutions. Field observations indicate strong karstification and vuggy intercalations especially in the middle part of the Asmari succession. The biggest karst in the dam axis which identified by speleological investigations is Golshany Cave with volume of about 150,000 m3. The tendency of the Asmari limestone for strong dissolution can alert about the seepage from the reservoir and area of the dam locality


Evidences of hypogenic speleogenesis in Slovenian caves , 2013, Otoničar, B.

 In Slovenia, known as the country of classical karst, thinking about caves of predominantly hypogenic origin have been treated almost as a heresy. Although we may agree that only on the basis of cave morphology and wall rock features parts of some “common” caves especially close to allogenic inflow and past epipheratic zones cannot be simply related to some past hypogenic phase of cave development (e. g. Osborne 2008; Knez & Slabe 2009) some caves in Slovenia host too many features diagnostic for hypogenic, hydrothermal or at least ascending water flow that such interpretations shouldn’t be considered.

We will present preliminary studies on caves from different karstic regions of Slovenia where cave morphology, wall rock features, mineralogy, general geological setting of the area and partly hydrogeology and hydrogeochemistry suggest, at least on a level of hypothesis, their partial development with hypogenic processes in a wider sense (sensu Palmer 2011). In each of the discussed karstic regions different phenomena diagnostic for some of the hypogenic processes prevails over the others.

In Jelovica high karstic plateau (Julian pre-Alps) and Raduha Mt. (Kamniško-Savinjske Alpe) many caves are locally decorated with big calcite crystals commonly found also as veins on the karstic surface.

The Vrh Svetih Treh Kraljev in Rovtarsko Hribovje, the Pre-alpine region in the western part of central Slovenia, hosts few caves which channels exhibit ramiform and maze like orientation guided by faults and joints with wall rock features characteristic for dissolution with slowly flowing ascending water. A large part of at least one cave is developed in dedolomite while the biggest cave in the area has no known natural entrance. In addition, three wells in the area discharge “sulphuric” water.

In Slovenia many caves show wall rock features that can also be diagnostic for hypogenic speleogenesis or at least to ascending flow. However, such features are most often found in places where high fluctuation of karstic waters mainly with allogenic river inflow occurs. Perhaps some exceptions could be found in the foothills of Jelovica Plateau where especially in one particular maze or anastomotic cave (Jeralovo brezno) no evidence of substantial allogenic inflow occurs although in the lower parts some smaller channels are partly filled by predominately fine grained sandy stream related allogenic deposits.

For more detail information of the above mentioned karstic regions with potential traces of hypogenic spelogenesis see the guidebook of the excursions.


Karst Memories Above and Beneath the See: Marseilles and Continental Shelf During the Cosquer Cave Occupation, 2014, Collinagirard, Jacques

In the south of France, the Cosquer Cave with its famous prehistoric paintings is located in a karstic area located between Marseilles and Cassis. This emerged and submerged karst is typical of karstic coasts submerged after the Late-Glacial Maximum. Ail the forms observed in the hinterland can be observed directly by scuba divers and indirectly on bathymetrie charts: lapiaz, karstic archs, sinkholes, uvala and polje. The emerged and submerged landscapes are mainly the heritage of specifie lithological conditions (Urgonian limestones) and tectonic conditions (vertical faulting network leading to coastal eollapse in theMediterranean Sea). üther elements of this submerged Iandscape are given by the traces of the last sea level rise (palaeo-shorelines and erosion platforms and notehes). AIl the area between Marseilles and La Ciotat is now established as the Calanques National Park, inc1uding the Cosquer Cave with its upper Palaeolithic rock art paintings, which adds an international archaeological interest to this exceptional natural area.


PRELIMINARY CONSIDERATIONS ON HYPOGENE MORPHOLOGY IN TOCA DA BOA VISTA E TOCA DA BARRIGUDA CAVES, NORTHEASTERN BRAZIL, 2014, Borges S. , Casarin C. , Menezes C. , Srivastava N. , Silva R. , Bezerra F. , Auler A.

The Toca da Boa Vista and Barriguda caves are located in Northeastern Brazil. They occur in the Neoproterozoic carbonates (limestones and dolomites) of the Salitre Formation, located at Irecê Basin. This set of rocks occurs within the São Francisco Craton, a region that was not affected by the Brasiliano-Pan-African orogeny (Pedreira et al., 1987). The caves occur at a dis­tance of approximately 300 m apart and there is a possibility of a link between them, but so far this has not been proven. Toca da Boa Vista has about 108 km of mapped passages and is therefore the largest cave in South America. Toca da Barriguda is smaller and has about 32 km of mapped galleries.

The architecture of the Toca da Boa Vista and Barriguda caves present both a 2D network and spongework type (Auler, 2009). The control of the conduits is related to faults, fractures and axial planes of antiforms. The general configuration of the caves seems to follow the Pacuí riverbed that has its channel located about 1km southeast. The origin of these hypogenic caves was first postulated by Auler & Smart (2004), who described some hypogenic features and reported a acid source (H2S) coming from existing pyrite in carbonates to explain the corrosion and dissolution of carbonate rocks. Klimchouk (2009) wrote about the need to investigate deeper this issue. He drew attention to the apparent feeders presence coming from the lower aquifer as well as to the importance of determi­nation of the source of acidity, since the amount of pyrite present doesn’t seem to be significant for the origin and development of the caves by hypogenic speleogenesis.

Although the origin and development of the caves are still under discussion, abundant hypogenic forms are present. Feeders, rising wall channels, half ceiling tubes, half wall tubes, ceiling cupolas, convection cupolas and wall niches are the major forms found. The linear geometry of caves suggests that they have a structural control. In addition, cavities generated at Toca da Boa Vista and Barriguda caves seem to follow the same stratigraphic level, as well as existing permeable structures such as fractures, faults and axial planes of antiforms. The process of ascending flow through these structures has resulted in the opening of the cavities by hypogenic dissolution as well as the collapse of blocks caused by the lack of sustainability of the layers generated by the voids left by the dis­solution. Outlets that would flow to levels above were not found. The origin and evolution of the cave system, however, needs further investigation.


PERMIAN HYDROTHERMAL KARST IN KRAKÓW REGION (SOUTHERN POLAND) AND ITS PECULIAR INTERNAL SEDIMENTS, 2014, Gradziński M. , Lewandowska A. , Paszkowski M. , Duliński M. , Nawrocki J. , Żywiecki M.

The development of caves influenced by the deep circulation of water has received increasing interest for the last thirty years. Presently, hypogene caves have been recognized all around the world. Conversely, the ancient examples filled with sediments and representing palaeokarst forms are not so common.
The karst forms and their sediment fillings were encountered in the Dębnik Anticline (Kraków region, Southern Poland) composed of Middle Devonian to Mississippian carbonates. The development of karst slightly postdates the Permian (ca. 300 Ma) volcanic activity in the Kraków region. In this region major transcontinental strike and slip Hamburg-Kraków-Dobruja fault zone induced a series of minor, en echelon, extensional faults, which served as magma passages and guided karst conduits.
The karst forms in the Dębnik Anticline reach several to tens of meters in size. They are filled with: i) massive, subaqueous, coarse crystalline calcite spar; ii) crystalloclastic, bedded limestones; iii) jasper lenses; iv) kaolinitised tuffs. The sediments are characterized by red colouration caused by iron compounds.
Coarse crystalline calcite spar composes beds up to several dozen centimeters in thickness. They are laminated and comprise frutexites type structures. The calcites are interbedded with pinkish-red crystalloclastic limestones, which are built of detritic calcite crystals from silt size to a few millimeters across. Some of the crystals are of skeletal type. Crystalloclastic limestones are normally graded. Both calcite spar and crystalloclastic limestones underwent synsedimentary deformations, which resulted in brecciation and plastic deformations.
The above deposits fill karst forms up to a few metres in lateral extent. However, analogously filled enormously huge (up to around 100 m across) forms were recognized in the early 80s of the last century. Presently, they are completely exploited.
The karst forms were fragments of extensive circulation system. It was fed by waters of elevated temperature, rich in endogenic CO2, which is proved by fluid inclusion analysis and stable isotope investigation. The origin of this system was associated with volcanic activity. The roots of the system are represented by fissures filled with coarse crystalline, red and white calcites of onyx type, which are common in the Dębnik Anticline. Water issuing from this system on the surface caused precipitation of red travertines. These travertines are preserved only as clasts in the Lower Permian conglomerates deposited in the local tectonic depressions.
The study was financed by Ministry of Science and Higher Education project N307 022 31/1746.


HYPOGENE SPELEOGENESIS AND CO2: SUGGESTIONS FROM KARST OF ITALY, 2014, Menichetti, M.

The carbon dioxide produced in the soil and dissolved in the percolation water is considered as the main agent for karstification in the carbonate rocks. Superficial morphologies and underground caves are product of the corrosion of the limestone, while carbonate speleothems is the other end member of the process.
Hypogene speleogenesis driven by deep seated fluids is the cave formation processes for the main karst systems in the Apennines of Italy. Hydrogen sulfide and endogenic carbon dioxide are the main agents for underground karst corrosion and the soil carbon dioxide plays a secondary rule. The limestone corrosion driven by hydrogen sulfide produces gypsum deposits in caves that could be assumed as the indicator of the hypogene speleogenesis. The action of endogenic carbon dioxide in the cave formation, especially if it operates at lower temperature, is not easy to detect and the resulting cave morphology is not helpful to recognize the cave formation process.
The main sources of carbon dioxide in the underground karst system in the Apennines of Italy can be related to different processes driven by the endogenic fluids emissions. The crustal regional degassing seems to be the prevalent source for carbon dioxide in the karst massifs with the main release in the groundwater. Hydrogen sulfide and methane oxidation, possibly mediated by bacteria activity, are other sources in the buried Cenozoic sediments. Releasing of carbon dioxide along the faults and in the fractures occurring in the carbonate rocks is an important source, especially in the seismically active area. Finally, thermogenic reactions with carbonate rocks are well known as one of the main production mechanism of carbon dioxide released in the atmosphere.
Data from carbon dioxide monitoring in several caves show a relevant contribution of the endogenic carbon dioxide (about 75 %) in the karst system which drives the speleogenesis reactions and shapes the underground morphologies.


HYPOGENE PALEOKARST IN THE TRIASSIC OF THE DOLOMITES (NORTHERN ITALY), 2014, Riva, A.

In the Triassic of successions of the Italian Dolomites (Northern Italy), there are several examples of different types of hypogene paleokarst, sometimes associated with sulfur or hematite ore deposits.The paleokarst features are related to a regional volcanic event occurred during the Ladinian (Middle Triassic) that affected several carbonate platforms of Anisian-Ladinian age.This study is focusing mainly on the Latemar paleokarst, in the Western Dolomites, and on the Salafossa area in the Easternmost Dolomites.
The karst at Latemar developed as the result of a magmatic intrusion located just below the isolated carbonate platform, developing a system of phreatic conduits and some underground chambers, not justified by the entity of the submarine exposure occurring at the top of the carbonate platform. Most of these features are located about 500 m below the subaerial unconformity and are filled with middle Triassic lavas. Only in one case, the filling is represented by banded crusts now totally dolomitized, with abundant hematite. In this case, the only way to explain the presence of the karst at this depth is to invoke a deep CO2 source allowing the dissolution of the carbonate at such depths: the fact that some phreatic conduits and a possible underground chamber are filled only with lavas is pointing toward an important role of volcanism in karst development.
Salafossa is a well-known mine located in the easternmost Dolomites and has been exploited until 1986, when all the activity ceased. The main metals, in this case, are Zn-Pb-Ba-Fe, exploited within a quite complex paleokarst system developed in several levels, filled by a complex mineralized sequence. The strong dissolution led to the development of voids aligned with the main fault controlling the mineralization, with a proper karst system with phreatic morphologies.


Radon, carbon dioxide and fault displacements in central Europe related to the Tohoku Earthquake, 2014, Briestensky Milos, Thinova Lenka, Praksova Renata, Stemberk Josef, Rowberry Matt D. , Knejflova Zuzana

Tectonic instability may be measured directly using extensometers installed across active faults or it may be indicated by anomalous natural gas concentrations in the vicinity of active faults. This paper presents the results of fault displacement monitoring at two sites in the Bohemian Massif and Western Carpathians. These data have been supplemented by radon monitoring in Mladec Caves and by carbon dioxide monitoring in Zbrasov Aragonite Caves. A significant period of tectonic instability is indicated by changes in the fault displacement trends and by anomalous radon and carbon dioxide concentrations. This was recorded around the time of the catastrophic MW = 9.0 Tohoku Earthquake which hit eastern Japan on 11 March 2011. It is tentatively suggested that the Tohoku Earthquake in the Pacific Ocean and the unusual geodynamic activity recorded in the Bohemian Massif and Western Carpathians both reflect contemporaneous global tectonic changes.


Integration of Seismic-Reflection and Well Data to Assess the Potential Impact of Stratigraphic and Structural Features on Sustainable Water Supply from the Floridan Aquifer System, Broward County, Florida, 2014, Cunningham, K. J.

The U.S. Geological Survey and Broward County water managers commenced a 3.5-year cooperative study in July 2012 to refine the geologic and hydrogeologic framework of the Floridan aquifer system (FAS) in Broward County. A lack of advanced stratigraphic knowledge of the physical system and structural geologic anomalies (faults and fractures originating from tectonics and karst-collapse structures) within the FAS pose a risk to the sustainable management of the resource.

The principal objective of the study is to better define the regional stratigraphic and structural setting of the FAS in Broward County. The objective will be achieved through the acquisition, processing, and interpretation of new seismic-reflection data along several canals in Broward County. The interpretation includes integration of the new seismic-reflection data with existing seismic-reflection profiles along Hillsboro Canal in Broward County and within northeast Miami-Dade County, as well as with data from nearby FAS wellbores. The scope of the study includes mapping the geologic, hydrogeologic, and seismic-reflection framework of the FAS, and identifying stratigraphic and structural characteristics that could either facilitate or preclude the sustainable use of the FAS as an alternate water supply or a treated effluent repository. In addition, the investigation offers an opportunity to: (1) improve existing groundwater flow models, (2) enhance the understanding of the sensitivity of the groundwater system to well-field development and upconing of saline fluids, and (3) support site selection for future FAS projects, such as Class I wells that would inject treated effluent into the deep Boulder Zone.


Deep conduit flow in karst aquifers revisited, 2014, 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, 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.


Sinkholes, pit craters, and small calderas: Analog models of depletion-induced collapse analyzed by computed X-ray microtomography, 2014,

Volumetric depletion of a subsurface body commonly results in the collapse of overburden and the formation of enclosed topographic depressions. Such depressions are termed sinkholes in karst terrains and pit craters or collapse calderas in volcanic terrains. This paper reports the first use of computed X-ray microtomography (?CT) to image analog models of small-scale (~< 2 km diameter), high-cohesion, overburden collapse induced by depletion of a near-cylindrical (“stock-like”) body. Time-lapse radiography enabled quantitative monitoring of the evolution of collapse structure, velocity, and volume. Moreover, ?CT scanning enabled non-destructive visualization of the final collapse volumes and fault geometries in three dimensions. The results illustrate two end-member scenarios: (1) near-continuous collapse into the depleting body; and (2) near-instantaneous collapse into a subsurface cavity formed above the depleting body. Even within near-continuously collapsing columns, subsidence rates vary spatially and temporally, with incremental accelerations. The highest subsidence rates occur before and immediately after a surface depression is formed. In both scenarios, the collapsing overburden column undergoes a marked volumetric expansion, such that the volume of subsurface depletion substantially exceeds that of the resulting topographic depression. In the karst context, this effect is termed “bulking”, and our results indicate that it may occur not only at the onset of collapse but also during progressive subsidence. In the volcanic context, bulking of magma reservoir overburden rock may at least partially explain why the volume of magma erupted commonly exceeds that of the surface depression.


Results 346 to 360 of 376
You probably didn't submit anything to search for