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Enviroscan Ukrainian Institute of Speleology and Karstology


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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 magnetic north is the direction to the north magnetic pole at a given place and time. this differs from the direction towards which the north end of a compass points by a small individual compass error and by the effect of any local magnetic attraction [25].?

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


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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;
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Your search for establishment (Keyword) returned 37 results for the whole karstbase:
Showing 16 to 30 of 37
Spatial distribution, morphometry and activity of La Puebla de Alfinden sinkhole field in the Ebro river valley (NE Spain): applied aspects for hazard zonation, 2005,
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Gutierrezsantolalla F. , Gutierrezelorza M. , Marin C. , Desir G. , Maldonado C. ,
A highly active collapse sinkhole field in the evaporitic mantled karst of the Ebro river valley is studied (NE Spain). The subsidence is controlled by a NW-SE trending joint system and accelerated by the discharge of waste water from a nearby industrial state. The morphometry, spatial distribution and temporal evolution of the sinkholes have been analysed. The volume of the sinkholes yields a minimum estimate of average lowering of the surface by collapse subsidence of 46 cm. The clustering of the sinkholes and the tendency to form elongated uvalas and linear belts, in a NW-SE direction have a predictive utility and allow the establishment of criteria for a hazard zonation. With the precipitation record supplied by a pluviograph and periodic cartographic and photographic surveys the influence of heavy rainfall events on the triggering of collapses has been studied

Evolution of the Adriatic carbonate platform: Palaeogeography, main events and depositional dynamics, 2005,
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Vlahovic I. , Tisljar J. , Velic I. , Maticec D. ,
The Adriatic Carbonate Platform (AdCP) is one of the largest Mesozoic carbonate platforms of the Perimediterranean region. Its deposits comprise a major part of the entire carbonate succession of the Croatian Karst (External or Outer) Dinarides, which is very thick (in places more than 8000 m), and ranges in age from the Middle Permian (or even Upper Carboniferous) to the Eocene. However, only deposits ranging from the top of the Lower Jurassic (Toarcian) to the top of the Cretaceous can be attributed to the AdCP (defined as an isolated palaeogeographical entity). Although the entire carbonate succession of the Karst Dinarides was deposited within carbonate platform environments, there were different types of carbonate platforms located in different palaeogeographical settings. Carboniferous to Middle Triassic mixed siliciclastic-carbonate deposits were accumulated along the Gondwanian margin, on a spacious epeiric carbonate platform. After tectonic activity, culminating by regional Middle Triassic volcanism recorded throughout Adria (the African promontory), a huge isolated carbonate Southern Tethyan Megaplatform (abbreviated as STM) was formed, with the area of the future AdCP located in its inner part. Tectonic disintegration of the Megaplatform during the middle to late Early Jurassic resulted in the establishment of several carbonate platforms (including the Adriatic, Apenninic and Apulian) separated by newly drowned deeper marine areas (including the Adriatic Basin as a connection between the Ionian and Belluno basins, Lagonero, Basin, and the area of the Slovenian and Bosnian troughs). The AdCP was characterised by predominantly shallow-marine deposition, although short or long periods of emergence were numerous, as a consequence of the interaction of synsedimentary tectonics and eustatic changes. Also, several events of temporary platform drowning were recorded, especially in the Late Cretaceous, when synsedimentary tectonics became stronger, leading up to the final disintegration of the AdCP. The thickness of deposits formed during the 125 My of the AdCP's existence is variable (between 3500 and 5000 m). The end of AdCP deposition was marked by regional emergence between the Cretaceous and the Palaeogene. Deposition during the Palaeogene was mainly controlled by intense synsedimentary tectonic deformation of the former platform area-some carbonates (mostly Eocene in age) were deposited on irregular ramp type carbonate platforms surrounding newly formed flysch basins, and the final uplift of the Dinarides reached its maximum in the Oligocene/Miocene. The Adriatic Carbonate Platform represents a part (although a relatively large and well-preserved one) of the broader shallow-water carbonate platform that extended from NE Italy to Turkey (although its continuity is somewhat debatable in the area near Albanian/Greece boundary). This large carbonate body, which was deformed mostly in the Cenozoic (including a significant reduction of its width), needs a specific name, and the Central Mediterranean Carbonate Platform is proposed (abbreviated to CMCP), although the local names (such as AdCP for its NW part) should be kept to enable easier communication, and to facilitate description of local differences in platform evolution,

Error and Technique in Fluorescent dye Tracing, 2005,
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Smart Chris

The appropriate approach to dye tracing in karst areas depends upon the objective and context of the trace. Dye tracing in karst areas is undertaken to address geographical, hydrogeological and contaminant problems at particular spatial and temporal resolution in the context of prior knowledge, available resources, social and legal expectations and environmental constraints. The value of a trace is improved if the objective can be formalized into a rational hypothesis and where the signal is demonstrably distinct from error. This requires sampling and analysis as much to define error as to detect the signal. The tolerable error depends on the dye trace objective and context, and scales with the sophistication of both, becoming increasingly critical and challenging as higher level interpretations are made. The appropriate technique for a particular trace therefore depends not only on the problem and context, but also upon the necessity of defining and correcting errors. Simpler problems such as establishment of underground connections can often be usefully tackled with simple techniques. Variable background fluorescence is a particularly difficult systematic error in dye tracing that can be reduced by supplementary sampling and control. This approach is illustrated for fluorescence spectra and in situ filter fluorometry. To extract a signal from spectra a statistical correction has been developed allowing compositional and concentration corrections to highlight anomalous samples. Supplementary sampling is required to provide the background statistics necessary for such an approach. The strong spectral coherence of background allows concurrent green fluorescence measurements to define variable background fluorescence during a red dye trace. The relationship between red and green fluorescence in un-dyed samples can be used to model background behavior in the presence of the red dye.


Protection of Karst in the Philippines., 2006,
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Restificar S. D. F. , Day M. J. , Urich P. B.
The article presents an overview of the current status of karst protection in the Philippines. Prior studies indicate that of the 35,000km2 of karst landscape in the country, about 29% is protected . However, protection of karst has not to date been a priority of the Philippine government, and the country has no existing legislation that is directly decreed for protection and conservation of karstlands. Most contemporary karst protection is indirect, in that the karst is located within protected areas established for other, although often related reasons, such as ecological conservation, water supply protection and tourism. However, it appears that the Philippine government is gradually recognizing explicitly the need to protect karst landscapes. The establishment of the National Caves and Cave Resources Management and Protection Act in 2001 and the inclusion of karst water resources in the countrys National Action Plan (NAP) under the United Nations Convention to Combat Desertification (UNCCD) are significant steps towards explicit protection of karst areas. Although the existing legislation only addresses specific facets of karst landscape, it may stimulate additional programs and legislation that will more broadly protect karst landscapes nationally. Philippines, karst, caves, protected areas, environmental legislation

Cave and karst images: the rediscovery of an important historical record, 2006,
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Nixon, Gill.
A fascinating collection of British Geological Survey records, dating back to its establishment in 1835, is archived in the Library Strongroom at the Survey office at Keyworth, Nottinghamshire. Among the contents are letters, files, maps, medals, lantern slides, prints and other ephemera that seldom see the light of day, except at the specific request of BGS staff or visiting researchers.

The Messinian salinity crisis: Looking for a new paradigm?, 2006,
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Roveri M. , Manzi V. ,
The importance of the sedimentary record of Messinian events in the Apennines foredeep is due to its geological and structural settings, which allow the reconstruction of the relationships between marginal and basinal settings and provide fundamental insights into some important issues. A geologic-stratigraphic model of the Messinian Apennine foredeep indicating a possible solution for closing the last `Messinian gap' is here presented. Moreover, the establishment of a preliminary high-resolution stratigraphy for the terminal Lago Mare stage allows us to attempt Mediterranean-scale correlations across different structural settings.The Messinian evolution of the Apennine foredeep and some considerations of adjacent areas suggest the great importance of tectonic deformation in controlling Messinian events. The intra-Messinian unconformity is a common feature of the marginal basins of the Mediterranean, and it is associated in many cases to the collapse and resedimentation of primary evaporites. The genesis of such unconformity seems to be strictly related to a general tectonic reorganization of the Mediterranean area. Preliminary observation on the stratigraphy of the Lago Mare stage suggest that the high-frequency lithological cyclicity observed in the non-marine deposits of this stage, as well as the superimposed transgressive trend, are common to many Mediterranean basins. These characteristic features might reflect the interplay between a longer-term tectonic trend and higher-frequency, precession-related, climatic changes; this could represent a fundamental tool for establishing a high-resolution stratigraphic framework of the latest Messinian allowing long-distance correlations between terrestrial and marine ecosystems and hence more accurate palaeoenvironmental studies

Flow capture and reversal in the Agen Allwedd Entrance Series, south Wales: evidence for glacial flooding and impoundment, 2007,
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Simms, Michael J And John B Hunt.
Detailed observations of passage morphology, scallop orientations, and cross-cutting relationships of vadose notches and roof heights within a small area of the Agen Allwedd cave system, south Wales, reveal a complex history of flow re-routing linked to several successive phreatic-vadose cycles. At least three discrete phases of phreatic development can be recognized, each succeeded by a period of vadose entrenchment. Two distinct episodes of flow diversion are evident and were initiated during separate phreatic phases. The repeated establishment of phreatic conditions at such a high level within the cave system can be attributed either to glacial impoundment of meltwater recharge and/or the creation of a localized perched phreas as a result of temporary blockages. We conclude that glacial meltwater from the Usk valley glacier entered the cave along its northern edge and was impounded as a result of valley glaciers blocking lower outlets, causing flooding of the entire cave system during glaciations. Vadose entrenchment then occurred as much of the cave was drained during ensuing interglacial(s). Drainage rerouting occurred in response to temporary, but prolonged, blockages that allowed meltwater recharge to generate high hydrostatic pressures. Newly opened or exposed fractures in the limestone were thereby exploited, creating bypass routes. This model, which is consistent with what is known of ice depths across the region during the Pleistocene, has significant implications for the evolution of the entire cave system and indeed for other caves in broadly analogous situations in south Wales and beyond.

Cave archaeology and the NSS: 19412006, 2007,
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Crothers George, Willey P. , And Watson Patty Jo
Like most other branches of speleology, cave archaeology in the U.S. grew and developed significantly during the mid to late twentieth century. Originally viewed as marginal to mainstream Americanist archaeology, pursuit of prehistoric and historic archaeology underground is now widely accepted as making valuable contributions to knowledge of human past. The National Speleological Society played a central role in that development and continues to do so. We outline the establishment and growth of cave archaeology in North America, with special emphasis on relations between the NSS and archaeology performed in dark zone, deep cave interiors

UNDERGROUND WATER FLOW BETWEEN BLOKE PLATEAU AND CERKNICA POLJE AND HyDROLOGIC FUNCTION OFKRINA JAMA, SLOVENIA, 2008,
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Kogovek Janja & Prelovek Mitja & Petri? Metka
Krina jama and Krina jama 2 are of important natural value. They have been known for more than hundred years from speleobiological, paleontological, geomorphological and touristic points of view. In 2007 the establishment of a water treatment plant on Bloke plateau raised important question: can partly cleaned water from the water treatment plant contaminate both caves and decrease their value? To answer this question a tracer test was carried out at the Bloke plateau. It showed general underground water flow from Farov?ica ponor at Bloke plateau toward the teber?ica spring at Cerknica polje. Minority of recovered tracer appeared at erovni?ica and Izvir v Podlou springs. The tracer was not detected at Studenec v Lou and Zlatovec springs. Between ponor and springs three karst caves were observed. The highest concentration of tracer was detected in the cave Mrzla jama pri Blo?icah and a much smaller concentration in the Krina jama and Krina jama 2. This shows that at middle water level the underground Farov?ica stream does not flow directly through Krina jama and Krina jama 2 but near or below them. Since the tracer appeared in both caves only after the precipitation, underground water course can be significantly different at high water level. Tracing test also showed some characteristics of underground water flow through dolomite and characteristics of a composed aquifer with alogenic-autogenic recharge.

Karst drainage relations with catchment land use change, Mole Creek, Tasmania, Australia, 2008,
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Hunter, Deborah L, Trevor W Lewis And Joanna Ellison.
Since 2001, the previously perennial Parsons' Spring of the Mole Creek fluviokarst in northwestern Tasmania, Australia, has become intermittent in discharge. This change follows the establishment of 636 ha of eucalypt plantations since 1995 above the Spring, including where Quaternary slope deposits obscure the geological contact of the limestone with overlying rocks. In this 2008 study, water quality was compared and contrasted between Parsons' Spring and other sites in the study catchment and a resurgence in a nearby reference catchment over different flow conditions and in response to a rainstorm. Results show that the study spring has a mixed recharge regime and complex discharge controls, including diffuse and conduit hydrological components. Parsons' Spring is probably the main wet season overflow spring of a distributary system connected to the phreatic aquifer underlying the area. Apparent chemical 'signatures' indicating soil disturbance in the study spring's waters implied the presence of an epikarst reservoir beneath the slope deposits cultivated for plantation establishment. Given their location, extent and growth stage, the plantations are expected to reduce aquifer recharge substantially by 2013-2018 as interception of recharge increases. The consequent reduction of available aquifer yield would result in economic stress for the rural community and compromise of karst ecosystems. (This paper was first presented audio-visually at a conference of the Australian Speleological Federation in January 2009, and a shorter version has been submitted for the conference proceedings).

Important directions of karst and speleological researches and tasks of their development in Ukraine, 2008,
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Klimchouk A. B.

The end of the XX Century has seen a remarkable growth of significance of speleology among modern Earth sciences. The paper provides a brief overview of recent advances and trends in geospeleology and karstology. It is shown that knowledge on cave origin has attained a status of a full-fledged theory, and that the speleogenetic theory took a central place in karst hydrogeology and dramatically improved understanding of karst aquifers evolution and functioning. Other areas of considerable advances and great significance for adjacent disciplines are paleo-reconstructions from karst/cave records and speleogenetic implications for assessment of karst subsidence hazard. The modern speleology has an obvious interdisciplinary character. The establishment in 2006 of the Ukrainian Institute of Speleology and Karstology is grounded on considerable achievements of Ukrainian scientists in this field and opens new perspectives for further development of speleology and karstology in Ukraine.


On the essence of karst, 2010,
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Klimchouk, O. B. , Andreychouk, V. N.

The long-lasting uncertainty with the central for karstology notion of karst hinders synthesis of knowledge and the development of a theoretical basis of this scientific discipline. This paper analyses the essence of karst, based on generalization of the modern ideas about regularities of the origin and evolution of conduit permeability in soluble rocks, viewed in the light of ideas of synergetics and non-equilibrium thermodynamics of I.P.Prigogine regarding self-organization in open systems and formation of ordered dissipative structures.

The presence of soluble rocks in the sedimentary environment determines a phenomena of self-organization of the flow structure, which brings the water-rock system into a new capacity-state, namely karstic. The property of self-organization of this geosystem realizes via specific (speleogenetic) mechanism of permeability development, which action radically changes (organizes in a special manner) the structure and functioning of the flow system.

The mechanism of self-organization of flow and of the formation of the karst geosystem (speleogenesis) includes: 1) early speleogenesis, positive feedback between flow and the rate of enlargement of initial flow paths (revealing of proto-conduits), 2) speleogenetic initiation: a cascade breakthroughs of proto-conduits to the condition of rapid dissolution kinetics, with accelerated growth of initiated conduits, hydrodynamic competition, respective destabilization and reorganization of the flow pattern and change in boundary conditions, and, 3) speleogenetic development: stabilization of the system at dynamic equilibrium at the expense of increased energy exchange with the environment, and further growth of conduits. As a result of this specific evolution the geosystem acquires new, karstic, capacity and more complex of organization, with the establishment of one more level of permeability, the most contrast one.

The notion of karst is derived from the essence of progressive evolution of the geosystem containing permeable soluble rocks, driven by water exchange and speleogenetic mechanism of self-organization of the permeability structure. Regressive evolution of the karst geosystem includes processes of gravitational destruction and various accumulations, which lead to fragmentation and demolition of relict structures of karst permeability. Based on this new approach to definition of the notion of karst, criteria of distinction between proper karst and similar but not identical phenomena (merokarst, pseudokarst) are discussed.


Fluid migration and porosity evolution in the Buda Hills, Hungary – selected examples from Triassic and Paleogene carbonate rocks/Dissertation submitted to the Ph.D. program for Geology and Geophysics at the Ph.D. School of Earth Sciences, Eötvös Lor, 2011,
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Poros, Zsófia

Porosity evolution of carbonates in the Buda Hills was the subject of this research. The aim was to provide an analogue for carbonate reservoirs that underwent multiphase diagenesis. Two major porosity types were recognized: 1) micro-porosity of powdered Triassic dolomites 2) cavernous and fracture porosity represented by the famous hypogenic cave system, hosted by Triassic and Paleogene carbonates. Powderization of dolomite is a general phenomenon in the Buda Hills, where its areal extent is exceptionally large compared to similar occurrences elsewhere in the world. Geochemistry and mineralogy of the dolomite remained constant throughout the disintegration. Powderization is absent at places where the Triassic dolomites are partially calcitized as a result of karst related dedolomitization. Since powderization was controlled by surface related processes and no geochemical changes were associated with it, disintegration of dolomite is interpreted as the result of sub-recent physical weathering, supposedly related to frost action.

Hypogenic caves are found along older calcite-barite-fluorite-sulphide veins, pointing to the fact that young cave-forming fluids migrated along the same fractures as the older mineralizing fluids did. Predominantly NNW–SSE strike of fractures concludes a latest Early Miocene maximum age for the fracture-filling minerals. Vein-calcite contains coeval primary, HC-bearing- and aqueous inclusions indicating that also HCs have migrated together with the mineralizing fluids. The coexistence of aqueous and HC inclusions permitted to establish the entrapment temperature (80°C) and pressure (85 bar) of the fluid and thus also the thickness of sediments, having been eroded since latest Early Miocene times, was calculated (800 m). Low salinity of the fluids (<1.7 NaCl eq. wt%) implies that HC-bearing fluids were diluted by regional karst water. Fluid inclusion studies also revealed that aggressive gases (e.g. CO2, H2S) were associated with HCs and that these gases may have played a role in dissolution of the carbonates. Based on the location of the paleo- and recent HC indications, identical migration pathways were reconstructed for both systems. It was proved that HC-bearing fluids have migrated northwestward from the basin east to the Buda Hills from the Miocene on. Due to the uplift related intensification of groundwater circulation, the proportion of hydrothermal fluids has diminished in favour of cold meteoric fluids. Establishment of the actual porosity of the Buda Karst initiated in Miocene times and earlier diagenetic history of the carbonates affected only the powderization of dolomite, and it had no direct effect on the localization of hypogenic caves.


OBSERVATIONS OF PLIOCENE KARSTS FOSSILIZED BY QUATERNARY EOLIAN SILTS IN THE MATMATA MOUNTAINS (SOUTH-EAST TUNISIA), 2012,
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Sghari, Abdeljalil

The submeridional Dahar chain in southeastern Tunisia is over 200 km long. It is separated from the Mediterranean Sea by the Jeffara plain with some tens of kilometers in width. This landscape continues to the South into Libya, but to the North, the chain ends with the Matmata mountains which form a plateau slightly inclined to the west and some 10 km wide. The eastern scarp shows a mainly calcareous geological stratigraphy from Upper Permian to the Senonian. The Dahar-Matmata structure belongs to the Sahara platform and shows a hiatus during the whole Tertiary, since it was emerged since Upper Cretaceous. The Tunisian Atlas nearby shows a completely different paleogeographic evolution, with a complete Tertiary series and a later Plio-Quaternary structuration. These two paleogeographic domains of Southern Tunisia, the Sahara Atlas and the NE border of the Sahara platform, were influenced by the Messinian crisis (5.9 Ma to 5.3 Ma). This was expressed by the collapse of the Mediterranean Sea level, profoundly modifying the fluvial dynamics with an inversion of the erosional system, from normal erosion to regressive erosion. It results a deepening of canyons in the downstream part and a deepening of the watercourses in the upstream part. The geological structures in the Messinian have been deeply affected by these large eustatic changes, with an incision of cluses in the Atlas and the deposition of a thick clayeysandy series that we could recently link to deltaic systems and Gilbert deltas. The re-establishment of seaways between the Atlantic and the Mediterranean, and the subsequent infill in the Lower Pliocene (Zanclean transgression), with an important inpact in Southern Tunisia, had multiple consequences in that region. The newly adjusted sealevel, together with a more humid climate that was confirmed by faunal and floral extension oof tropical plants in Northern Africa, stimulated an important karstification of the limestone areas. In the Dahar chain, caves, dolines, karstic depressions or karstic dry valleys emerged, the most spectacular ones being found in the Matmata Mountains. The karstic depressions are the forms that represent best this Pliocene karstification that surely was interrupted in an early stage, because localized endokarstic forms had not enough time to develop. So the karstification seems to have been active in Matmata from 5.4 to 4.0 million years, i.e. two times as long than the duration of the Messinian crisis. The interruption of karstification is due to an increase in temperature and dryness, which even gets more intense during the Pliocene, pulverizing the soils. Already at the beginning of the desertification, a calcareous crust forms by rapid cristallization of dirt. It is immediately transported from the karstic zones to the Jeffara plain. This transfer fo dissolved calcite was the origin of the resistant calcitic crust well known in the Jeffara plain. We now identified the same crust in a karstic depression in the Matmata Mountains, opening the way to new geomorphologic and tectonic interpretations, and a review of the eolian silts formerly attributed to the Upper Pleistocene. Later, during Upper Pliocene-Gelasian, we observe a general tectonic uplift of the Dahar chain and the Matmata Mountains as well as the subsidence of the Jeffara plain at the Medenine fault (NW-SE), prolonging the large Gafsa fault towards the East. The karstic paleoforms were thus uplifted more than 500 m, but nevertheless remain open on the Jeffara plain, as seen by large depressions. As a consequence, the karstic depressions of Matmata played the role of traps for eolian silts blown from the Jeffara plain during the extreme desertification in the Upper Pliocene-Gelasian. The morphological reconstruction since the Messinian shows a succession of important events during the Pliocene that profoundly influenced the Quaternary. All indications permit to reject the hypothesis that the Matmata silts came from the West (Eastern Erg).

 


OBSERVATIONS OF PLIOCENE KARSTS FOSSILIZED BY QUATERNARY EOLIAN SILTS IN THE MATMATA MOUNTAINS (SOUTH-EAST TUNISIA), 2012,
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Sghari, Abdeljalil

The submeridional Dahar chain in southeastern Tunisia is over 200 km long. It is separated from the Mediterranean Sea by the Jeffara plain with some tens of kilometers in width. This landscape continues to the South into Libya, but to the North, the chain ends with the Matmata mountains which form a plateau slightly inclined to the west and some 10 km wide. The eastern scarp shows a mainly calcareous geological stratigraphy from Upper Permian to the Senonian. The Dahar-Matmata structure belongs to the Sahara platform and shows a hiatus during the whole Tertiary, since it was emerged since Upper Cretaceous. The Tunisian Atlas nearby shows a completely different paleogeographic evolution, with a complete Tertiary series and a later Plio-Quaternary structuration. These two paleogeographic domains of Southern Tunisia, the Sahara Atlas and the NE border of the Sahara platform, were influenced by the Messinian crisis (5.9 Ma to 5.3 Ma). This was expressed by the collapse of the Mediterranean Sea level, profoundly modifying the fluvial dynamics with an inversion of the erosional system, from normal erosion to regressive erosion. It results a deepening of canyons in the downstream part and a deepening of the watercourses in the upstream part. The geological structures in the Messinian have been deeply affected by these large eustatic changes, with an incision of cluses in the Atlas and the deposition of a thick clayeysandy series that we could recently link to deltaic systems and Gilbert deltas. The re-establishment of seaways between the Atlantic and the Mediterranean, and the subsequent infill in the Lower Pliocene (Zanclean transgression), with an important inpact in Southern Tunisia, had multiple consequences in that region. The newly adjusted sealevel, together with a more humid climate that was confirmed by faunal and floral extension oof tropical plants in Northern Africa, stimulated an important karstification of the limestone areas. In the Dahar chain, caves, dolines, karstic depressions or karstic dry valleys emerged, the most spectacular ones being found in the Matmata Mountains. The karstic depressions are the forms that represent best this Pliocene karstification that surely was interrupted in an early stage, because localized endokarstic forms had not enough time to develop. So the karstification seems to have been active in Matmata from 5.4 to 4.0 million years, i.e. two times as long than the duration of the Messinian crisis. The interruption of karstification is due to an increase in temperature and dryness, which even gets more intense during the Pliocene, pulverizing the soils. Already at the beginning of the desertification, a calcareous crust forms by rapid cristallization of dirt. It is immediately transported from the karstic zones to the Jeffara plain. This transfer fo dissolved calcite was the origin of the resistant calcitic crust well known in the Jeffara plain. We now identified the same crust in a karstic depression in the Matmata Mountains, opening the way to new geomorphologic and tectonic interpretations, and a review of the eolian silts formerly attributed to the Upper Pleistocene. Later, during Upper Pliocene-Gelasian, we observe a general tectonic uplift of the Dahar chain and the Matmata Mountains as well as the subsidence of the Jeffara plain at the Medenine fault (NW-SE), prolonging the large Gafsa fault towards the East. The karstic paleoforms were thus uplifted more than 500 m, but nevertheless remain open on the Jeffara plain, as seen by large depressions. As a consequence, the karstic depressions of Matmata played the role of traps for eolian silts blown from the Jeffara plain during the extreme desertification in the Upper Pliocene-Gelasian. The morphological reconstruction since the Messinian shows a succession of important events during the Pliocene that profoundly influenced the Quaternary. All indications permit to reject the hypothesis that the Matmata silts came from the West (Eastern Erg).


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