An appraisal of the conductance method for the in situ measurement of total hardness and aggressivity, 1977, Allbutt M.

Les réseaux souterrains de la région de Lébamba (Gabori), 1987, Peyrot B. , Massala J.

CONTRIBUTION TO THE STUDY OF KARSTIC SYSTEMS OF THE LEBAMBA REGION (GABON) - The Lebamba region is situated in the extreme southern part of Gabon close to the Republic of Congo. Geologically, it can be included within the Niari-Nyanga synclinorium, where the Precambrian schists and limestones show many karstic features and particularly a remarkable subterranean network, as to yet only partially surveyed. The dolomitic limestone of Lebamba, although of little importance, contains many cave systems: Lebamba, Bongolo, Mbenaltembe. A severe tectonic mesh together with fine micro-stratifications have opened the way to biochemical corrosion which, after observations and analysis, appears to result from a climate wetter than at present. The dimensions of the underground passages appear disproportionate, relatively to the low aggressivity of the present environment, thus illustrating the importance of paleoclimatic factors on the morphogenesis of central african karsts.

The experimental examination of microbal origin corrosion aggressivity of karst soils , 1998, Zá, Mbó, Lá, Szló,

Development of collapse sinkholes in areas of groundwater discharge, 2002, Salvati R. , Sasowsky I. D. ,

Collapse sinkholes are found in groundwater recharge zones throughout the world. They cause substantial loss of property each year, and occasional fatalities. In such settings, the formation of these features occurs through the downward migration of regolith into karst voids. The presence of a void in the bedrock. and sufficient seepage pressure or gravitative force in the regolith, is required for their creation. We investigated the development of cover collapse sinkholes in an unusual setting, areas of groundwater discharge rather than recharge. Upward hydraulic gradients and the likelihood of groundwater saturated with respect to calcite are difficult to reconcile with standard models for collapse development. Short flowpaths or renewed groundwater aggressivity towards calcite (via mischungskorrosion, thermally driven circulation, or deep-seated gaseous sources) are hypothetical mechanisms that could generate the subsurface voids that are needed to allow cover collapse development in discharge areas. For the two field sites in central Italy that we investigated, calculated carbon dioxide partial pressures in springs ranged from 7.38 X 10(-2) to 7.29 X 10(-1) atm. This indicates that deep-seated gaseous sources are most likely the mechanism allowing the development of the sinkholes. Groundwater is recharged in surrounding limestone massifs. The water moves through the carbonates and becomes saturated with calcite. As it circulates deeply in to the adjacent valleys, it mixes with deep-seated waters and gaseous fluxes from major fault systems, acquiring renewed aggressivity towards calcite. Finally, the water ascends into confined aquifers in the valley fill, and dissolves carbonate material present within, leading to surface collapse. (C) 2002 Elsevier Science B.V. All rights reserved

Morphometry and distribution of isolated caves as a guide for phreatic and confined paleohydrological conditions, 2005, Frumkin A, Fischhendler I,

Isolated caves are a special cave type common in most karst terrains, formed by prolonged slow water flow where aggressivity is locally boosted. The morphometry and distribution of isolated caves are used here to reconstruct the pateohydrology of a karstic mountain range. Within a homogenous karstic rock sequence, two main types of isolated caves are distinguished, and each is associated with a special hydrogeologic setting: maze caves form by rising water in the confined zone of the aquifer, under the Mt. Scopus Group (Israel) confinement, while chamber caves are formed in phreatic conditions, apparently by lateral flow mixing with a vadose input from above. (c) 2004 Elsevier B.V. All rights reserved

Development of the carbonate island karstmodel, 2007, Mylroie J. R. And Mylroie J. E.

The development of a comprehensive conceptual model for carbonate island karst began in the Bahamas in the 1970s. The use, initially, of cave and karst models created for the interior of continents, on rocks hundreds of millions of years old, was not successful. Models developed in the 1980s for the Bahamas, that recognized the youthfulness of the carbonate rock, the importance of fresh-water mixing with sea water, and the complications introduced by glacioeustatic sea-level change produced the first viable model, the flank margin cave model. This model explains the largest caves in carbonate islands as being the result of mixing zone dissolution in the distal margin of the fresh-water lens, under the flank of the enclosing land mass. The flank margin model, taken from the Bahamas to Isla de Mona, Puerto Rico, in the early 1990s, provided the first viable explanation for the very large caves there. Field work in the geologicallycomplex Mariana Islands in the late 1990s resulted in the development of the Carbonate Island Karst Model, or CIKM, which integrated the various components controlling cave and karst development on carbonate islands. These components are: 1) Mixing of fresh and salt water to create dissolutional aggressivity; 2) Movement of the fresh-water lens, and hence the mixing environments, by 100+ m as a result of Quaternary glacioeustasy; 3) The overprinting of glacioeustatic changes by local tectonic movements, where present; 4) The unique behavior of eogenetic (diagenetically immature) carbonate rocks; and 5) The classification of carbonate islands into simple, carbonate cover, composite, and complex categories. Current research involves the use of flank margin caves as predictors of past and present fresh-water lens configuration, the analysis of flank margin cave morphology as a measure of the processes that create them, and the CIKM as an indicator of paleokarst distribution.

Karstification in unconfined limestone aquifers by mixing of phreatic water with surface water from a local input: A model, 2010, Gabrovš, Ek F. , Dreybrodt W.

When water from the surface of a limestone plain seeps down through the fractured rock to the water table of an unconfined aquifer with low hydraulic gradient containing water saturated with respect to calcite, mixing of these waters causes renewed aggressivity. A model is presented, which describes the evolution of karstification by dissolutional widening of the fractures downgradient from the local input of surface water. The model couples flow in the fractures with dissolution rates. Dissolution rates are given by F = k (1 [1] c (x)/ceq)4, where c (x) is the calcium concentration at distance x from the entrance of the fracture, ceq is the equilibrium calcium concentration of the H2O–CaCO3–CO2 solution in the fracture, and k is a rate constant. The model describes two domains of waters saturated with respect to calcite at different partial pressure of CO2. At the borders of these domains the waters mix and create dissolutional widening of the fractures by mixing corrosion. A channel evolves along the border in the downgradient direction by about 100 m in 100 ky. Below this channel a zone of fractures with aperture widths up to 1 cm has originated. The change of the hydraulic conductivity in the mixing zone shifts the border of the domains, allowing the channel to grow in the downgradient direction. Below it the zone of widened fractures is invaded by saturated phreatic water and dissolution stops. This process continues at the downgradient part of the conduit. In summary, we find cave conduits evolving close to the water table, leaving significant cavernous structures below them. A variety of modelling scenarios with different choices of parameters show that this evolution is typical and changes only in details but not in its basic behaviour.

Hypogenic caves in France. Speleogenesis and morphology of the cave systems, 2010, Audra Ph. , D'antoninebecourt J. C. , Bigot J. Y.

Hypogenic caves develop by recharge from below, not directly influenced by seepage from the overlying land surface. Several processes of speleogenesis are combined, involving CO2 or H2S produced at depth. If the recharge from depth remains uniform, the growth of selected fissures is prevented, giving rise to maze cave systems with an upward development trend, which is defined as “transverse speleogenesis” [Klimchouk, 2003]. Hypogenic caves are much fewer than epigenic caves (i.e. developed downwards by meteoric water with aggressivity derived from soil). In France, as in the rest of the world, hypogenic caves were poorly recognized until recently because of their lower frequency, subsequent epigenic imprint often hiding the true origin, and the absence of a global conceptual model. However, about a hundred of hypogenic caves have been identified recently in France. The extreme diversity of hypogenic cave patterns and features is due to the variety of geological and topographic settings and types of flow. Thermal caves are a sub-set of hypogenic caves. Active thermal caves are few and small (Mas d’En Caraman, Vallon du Salut). Often, thermal in fluences only occur as point thermal in feeders into epigenic caves (Mescla, Estramar). In addition to the higher temperature, they may be characterized by CO2 (Madeleine) or H2S degassing, by warm water flowing in ceiling channels, or by manganese deposits. The Giant Phreatic Shafts locate along regional active fault lines. They combine all characteristics (thermal, CO2, H2S), due to the fast rising of deep water. The Salins Spring has been explored by scuba diving down to –70 m. Such a hyperkarstification is responsible for the development of the deepest phreatic shafts of the world: pozzo del Merro, Italy (-392 m). Inactive hypogenic caves may be recognized by their specific mineralization or by the presence of large calcite spar. Metallic deposits are due to the rising of deep waters that are warm, aggressive, and low in oxidation potential. Mixing with meteoric water generates Mississippi Valley Type (MVT) sulfidic ores. Iron deposits as massive bodies (Lagnes) or onto microbial media (Iboussières, Malacoste) making specific facies, such as “black tubes”, iron flakes, and iron pool fingers. Other frequent minerals are Mn oxides and Pb sulfur. In such low thermal conditions, calcite deposits occur as large spar in geodes or as passage linings. Other inactive hypogenic caves may also be recognized by characteristic patterns, such as mazes. The relatively constant recharge into confined karst aquifers suppresses fissure competition, so they enlarge at similar rates, producing a maze pattern. In horizontal beds, mazes extend centrifugally around the upwelling feeder. The juxtaposition of multiple discrete vertical feeders produces extended horizontal mazes. In gently tilted structures, 2D mazes extend below aquitards, or along bedding or more porous beds (Saint-Sébastien). In thick folded limestone the rising hypogenic flow alternatively follows joints and bedding planes, producing a 3D maze cave in a stair case pattern (Pigette). Isolated chambers are large cupola-like chambers fed by thermal slots. Thermal convection of air in a CO2-rich atmosphere causes condensation-corrosion that quickly produces voids above the water table (Champignons Cave). Sulfuric acid caves with replacement gypsum are produced by H2S degassing in the cave atmosphere. H2S oxidizes to H2SO4, which corrodes the carbonate rock and replaces it with gypsum. The strongest corrosion occurs above the water table, where sulfide degassing and thermal convection produce strong condensation-corrosion. Caves develop head ward from springs and from thermo-sulfuric slots upward (Chevalley-Serpents System). The low-gradient main drains record base level positions and even the slightest stages of water-table lowering (Chat Cave). Hypogenic speleogenesis provides better understanding of the distribution of karst voids responsible for subsidence hazards and the emplacement of minerals and hydrocarbons.

Hypogenic caves in France. Speleogenesis and morphology of the cave systems, 2010, Audra Philippe, D’antoninobecourt Jeanclaude, Bigot Jeanyves

Hypogenic caves develop by recharge from below, not directly influenced by seepage from the over lying land surface. Several processes of speleogenesis are combined, involving CO2 or H2S produced at depth. If the recharge from depth remains uniform, the growth of selected fissures is prevented, giving rise to maze cave systems with an upward development trend, which is defined as “transverse speleogenesis” [Klimchouk, 2003]. Hypogenic caves are much fewer than epigenic caves (i.e. developed downwards by meteoric water with aggressivity derived from soil). In France, as in the rest of the world, hypogenic caves were poorly recognized until recently because of their lower frequency, subsequent epigenic imprint of tenhiding the true origin, and the absence of a global conceptual model. However, about a hundred of hypogenic caves have been identified recently in France. The extreme diversity of hypogenic cave patterns and features is due to the variety of geological and topographic settings and types of flow. Thermal caves are a sub-set of hypogenic caves. Active thermal caves are few and small (Mas d’En Cara man, Vallondu Salut). Often, thermal in fluences only occur as point thermal infeeders into epigenic caves (Mescla, Estra mar). In addition to the higher temperature, they may be characterized by CO2 (Madeleine) or H2S degassing, by warm water flowing in ceiling channels, or by manganese de posits. The Giant Phreatic Shafts locate along regional active faul tlines. They combine all characteristics (thermal, CO2, H2S), due to the fast rising of deep water. The Salins Spring has been explored by scuba diving down to –70 m. Such a hyperkars tification is responsible for the development of the deepest phreatic shafts of the world: pozzo del Merro, Italy (-392 m). Inactive hypogenic caves may be recognized by their specific mineralization or by the presence of large calcite spar. Metallic deposits are due to the rising of deep waters that are warm, aggressive, and low in oxidation potential. Mixing with meteoric water generates Mississippi Valley Type (MVT) sulfidicores. Iron deposits as massive bodies (Lagnes) or ontomicrobial media (Ibous sières, Malacoste) making specific facies, such as “black tubes”, iron flakes, and iron pool fingers. Other frequent minerals are Mn oxides and Pb sulfur. In such low thermal conditions, calcite deposits occur as large spar in geodes or as passage linings. Other inactive hypogenic caves may also be recognized by characteristic patterns, such as mazes. The relatively constant recharge into confined karst aquifers suppres ses fissure competition, so they enlarge at similar rates, producing a maze pattern. In horizontal beds, mazes extend centrifugally around the upwelling feeder. The juxtaposition of multiple discrete vertical feeders produces extended horizontal mazes. In gently tilted structures, 2D mazes extend below aquitards, or along bedding or more porous beds (Saint-Sé bastien). In thick folded limestone the rising hypogenic flow alternatively follows joints and bedding planes, pro ducing a 3D maze cave in a stair case pattern (Pigette). Isolated chambers are large cupola-like chambers fed by thermal slots. Thermal convection of air in a CO2-rich atmosphere causes condensation-corrosion that quickly produces voids above the water table (Champignons Cave). Sulfuric acid caves with replacement gypsum are produced by H2S degassing in the cave atmosphere. H2S oxidizes to H2SO4, which corrodes the carbonate rock and replaces it with gypsum. The strongest corrosion occurs above the water table, where sulfide degassing and thermal convection produce strong condensation-corrosion. Caves develop headward from springs and from thermo-sulfuric slots upward (Chevalley-Serpents System). The low-gradient main drains record base-level positions and even the slightest stages of water-table lowering (Chat Cave). Hypogenic speleogenesis provides better understanding of the distribution of karst voids responsible for subsidence hazards and the emplace ment of minerals and hydrocarbons.

Deep confined karst detection, analysis and paleohydrology reconstruction at a basin-wide scale using new geophysical interpretation of borehole logs, 2011, Laskow M. , Gendler M. , Goldberg I. , Gvirtzman H. , Frumkin A.

Deep karst voids can be identified by a new geophysical interpretation method of commonly used borehole logs at deeply confined carbonate aquifers. We show that deep, buried karst voids can be characterized by combining this geophysical interpretation together with geological and hydrological data, and known speleological constraints. We demonstrate how this characterization can reveal past hydrological regimes and allow mapping of karst distribution on a basin-wide scale.

A combined analysis of geophysical, geological, hydrological and speleological data in the confined Yarkon-Taninim aquifer, Israel, led us to reconstruct past groundwater levels at different sea levels and reliefs, with the karst voids as a marker for long-term flow close to the water table. Paleo-canyons along the Mediterranean Sea shoreline strongly affected the region’s paleohydrology, by serving as major outlets of the aquifer during most of the Cenozoic. We conclude that intensive karstification was promoted by flow periods of longer duration and/or higher flux and flow velocities close to the aquifer’s past and present outlets. In addition, we suggest that karst voids found under shallow confinement was developed by renewed aggressivity achieved by hypogene water rising in cross-formational flow, mixed with fresh lateral water flow from the east.

Deep confined karst detection, analysis and paleo-hydrology reconstruction at a basin-wide scale using new geophysical interpretation of borehole logs, 2011, Laskow M. , Gendler M. , Goldberg I. , Gvirtzman H. , Frumkin A.

Deep karst voids can be identified by a new method of geophysical interpretation of commonly used borehole logs in deeply confined carbonate aquifers. We show that deep, buried karst voids can be characterized by combining this geophysical interpretation together with geological and hydrological data, and with known speleological constraints. We demonstrate how this characterization can reveal past hydrological regimes and allow mapping of karst distribution on a basin-wide scale.

Deep confined karst detection, analysis and paleo-hydrology reconstruction at a basin-wide scale using new geophysical interpretation of borehole logs, 2011, Laskow M. , Gendler M. , Goldberg I. , Gvirtzman H. , Frumkin A.

Deep karst voids can be identified by a new method of geophysical interpretation of commonly used borehole logs in deeply confined carbonate aquifers. We show that deep, buried karst voids can be characterized by combining this geophysical interpretation together with geological and hydrological data, and with known speleological constraints. We demonstrate how this characterization can reveal past hydrological regimes and allow mapping of karst distribution on a basin-wide scale. A combined analysis of geophysical, geological, hydrological, and speleological data in the confined Yarkon–Taninim aquifer, Israel, led us to reconstruct past groundwater levels at different relief and sea levels, with the karst voids as a marker for long-term flow close to the water table. Paleo-canyons along the Mediterranean Sea shoreline strongly affected the region’s paleo-hydrology, by serving as major outlets of the aquifer during most of the Cenozoic. We conclude that intensive karstification was promoted by flow periods of longer duration and/or higher flux and flow velocities close to the aquifer’s past and present outlets. In addition, we suggest that karst voids found under shallow confinement were developed by renewed aggressivity due to hypogene water rising in cross-formational flow becoming mixed with fresh lateral water flow from the east.

Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications, 2012, Galdenzi, Sandro

The measurement of the weight loss in limestone tablets placed in the Grotta del Fiume (Frasassi, Italy) provided data on the rate of limestone dissolution due to the sulfidic water and on the influence of local environmental conditions.

A linear average corrosion rate of 24 mm ka-1 was measured in stagnant water, while the values were higher (68-119 mm ka-1) where the hydrologic conditions facilitate water movement and gas exchanges. In these zones the increase in water aggressivity is due to mixing with descending, O2-rich, seepage water and is also favored by easier gas exchange between ground-water and the cave atmosphere. Very intense corrosion was due to weakly turbulent flow, which caused evident changes in the tablets shape in few months.

A comparison between the measured corrosion rates and the cave features showed that the values measured in the pools with stagnant water are too low to account for the largest solutional cave development, while the average values measured in the zones with moving water are compatible with the dimension of the cave rooms in the main cave levels, that must have developed when the base level was stable and hydrologic conditions favored the increase of water aggressivity.

Microsculpturing of solutional rocky landforms., 2013, Lundberg, J.

Karren (small-scale dissolutional features) have a great variety of forms and are known by a huge suite of terms. Bare rock forms are sharper and more gravitomorphic than subcutaneous forms, where rock-fracture control may dominate. Four controls operate: (1) physical properties of the solvent (fluid flow, surface tension, and percolation); (2) chemical properties of the solvent (unmodified rainwater, enhanced aggressivity, and reduced aggressivity); (3) chemical properties of the solute (rock solubility); and (4) physical properties of the solute (fractures and rock texture). Large expanses of bare rock karren are called karren fields, the more famous including China’s ‘Stone Forest’, Madagascar’s ‘Tsingy’, and Mulu’s ‘Pinnacles’. in caves