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 gypsum cave is both vadose and phreatic caves can form in gypsum, which is very soluble in water, but they are uncommon because gypsum rock rarely survives total dissolution in the near-surface environments associated with explorable caves. gypsum caves certainly exist at depth within buried evaporate sequences. in areas of wet climate gypsum caves are generally seen only if encountered by man-made excavations. in contrast, gypsum caves are more common and more extensive in areas that have experienced a long period of dominantly arid climate. the most spectacular gypsum caves are in the podolie region of the ukraine, where joint guided mazecave systems are very extensive - optimisticeskaja has around 215 km of passsage [9].?

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 shale (Keyword) returned 78 results for the whole karstbase:
Showing 16 to 30 of 78
Siluro - Devonian Bungonia Group, Southern Highlands, NSW, 1994,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Bauer, J. A.

The Bungonia Group is a sequence of Late Silurian - Early Devonian biostromal limestone, sandstone and shale constituting marine fill of the Wollondilly Basin, an extensional structure initiated during the Mid-Silurian. The Bungonia Limestone is elevated to Group status based on detailed mapping and analysis of the facies and faunal assemblages.

Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Vonplehweleisen E. , Klemm D. D. ,
The Postmasburg Mn/Fe-ores occur exclusively in dolomitic Precambrian sinkhole structures with siliceous breccias and shales as hostrocks. The main manganese minerals are braunite and bixbyite, apart from secondary alteration products of the psilomelane-manganomelane family. Various generations of ore minerals could be identified. The ore mineralization is subdivided into three different genetic types. They are classified either as pure karst deposits or as combined formations of karst origin and shallow marine sedimentation due to the transgression of the Banded Iron Formation (BIF) sea. Post-sedimentary metamorphism is identified as very low grade. The development of the different ore types is illustrated schematically

Evaporites, brines and base metals: What is an evaporite? Defining the rock matrix, 1996,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Warren J. K. ,
This paper, the first of three reviews on the evaporite-base-metal association, defines the characteristic features of evaporites in surface and subsurface settings. An evaporite is a rock that was originally precipitated from a saturated surface or near-surface brine in hydrological systems driven by solar evaporation. Evaporite minerals, especially the sulfates such as anhydrite and gypsum, are commonly found near base-metal deposits. Primary evaporites are defined as those salts formed directly via solar evaporation of hypersaline waters at the earth's surface. They include beds of evaporitic carbonates (laminites, pisolites, tepees, stromatolites and other organic rich sediment), bottom nucleated salts (e.g. chevron halite and swallow-tail gypsum crusts), and mechanically reworked salts (such as rafts, cumulates, cross-bedded gypsarenites, turbidites, gypsolites and halolites). Secondary evaporites encompass the diagenetically altered evaporite salts, such as sabkha anhydrites, syndepositional halite and gypsum karst, anhydritic gypsum ghosts, and more enigmatic burial associations such as mosaic halite and limpid dolomite, and nodular anhydrite formed during deep burial. The latter group, the burial salts, were precipitated under the higher temperatures of burial and form subsurface cements and replacements often in a non-evaporite matrix. Typically they formed from subsurface brines derived by dissolution of an adjacent evaporitic bed. Because of their proximity to 'true' evaporite beds, most authors consider them a form of 'true' evaporite. Under the classification of this paper they are a burial form of secondary evaporites. Tertiary evaporites form in the subsurface from saturated brines created by partial bed dissolution during re-entry into the zone of active phreatic circulation. The process is often driven by basin uplift and erosion. They include fibrous halite and gypsum often in shale hosts, as well as alabastrine gypsum and porphyroblastic gypsum crystals in an anhydritic host. In addition to these 'true' evaporites, there is another group of salts composed of CaSO4 or halite. These are the hydrothermal salts. Hydrothermal salts, especially hydrothermal anhydrite, form by the subsurface cooling or mixing of CaSO4- saturated hydrothermal waters or by the ejection of hot hydrothermal water into a standing body of seawater or brine. Hydrothermal salts are poorly studied but often intimately intermixed with sulfides in areas of base-metal accumulations such as the Kuroko ores in Japan or the exhalative brine deeps in the Red Sea. In ancient sediments and metasediments, especially in hydrothermally influenced active rifts and compressional belts, the distinction of this group of salts from 'true' evaporites is difficult and at times impossible. After a discussion of hydrologies and 'the evaporite that was' in the second review, modes and associations of the hydrothermal salts will be discussed more fully in the third review

Evaporite karst of northern lower Michigan, 1997,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Black Tj,
Michigan has three main zones of evaporite karst: collapse breccia in Late Silurian deposits of the Mackinac Straits region; breccia, collapse sinks, and mega-block collapse in Middle Devonian deposits of Northern Lower Michigan, which overlaps the preceding area; and areas of soil swallows in sinks of Mississippian deposits between Turner and Alabaster in Arenac and Iosco counties, and near Grand Rapids in Kent County. The author has focused his study on evaporite karst of the Middle Devonian deposits. The Middle Devonian deposits are the Detroit River Group: a series consisting of limestone, dolomite, shale, salt, gypsum and anhydrite. The group occurs from subcrop, near the surface, to nearly 1400 feet deep from the northern tip of the Southern Peninsula to the south edge of the ''solution front'' Glacial drift is from zero to 350 feet thick. Oil and gas exploration has encountered some significant lost-circulation zones throughout the area. Drilling without fluid returns, casing seal failures, and lost holes are strong risks in some parts of the region. Lost fluid returns near the top of the group in nearby areas indicate some karst development shortly after deposition. Large and irregular lost-circulation zones, linear and patch trends of large sink holes, and 0.25 mile wide blocks of down-dropped land in the northern Lower Peninsula of Michigan were caused by surface- and ground-water movement along faults into the Detroit River Group. Glaciation has removed some evidence of the karst area at the surface. Sinkhole development, collapse valleys, and swallows developed since retreat of the glacier reveal an active solution front in the Detroit River Group

Dedolomitization as a driving mechanism for karst generation in Permian Blaine formation, southwestern Oklahoma, USA, 1997,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Raines M. A. , Dewers T. A. ,
Cyclic deposits of Permian shales, dolomites, and halite and gypsum-bearing strata in the Blaine Formation of Southwestern Oklahoma contain abundant karst features. The present study shows that an important mechanism of karst development in these sequences is dedolomitization, wherein gypsum and dolomite in close spatial proximity dissolve and supersaturate groundwaters with respect to calcite. The net loss of mass accompanying this process (dolomite and gypsum dissolution minus calcite precipitation) can be manifest in secondary porosity development while the coupled nature of this set of reactions results in the retention of undersaturated conditions of groundwater with respect to gypsum. The continued disequilibrium generates karst voids in gypsum-bearing aquifers, a mineral-water system that would otherwise rapidly equilibrate. Geochemical modeling (using the code PHRQPITZ, Plummer et al 1988) of groundwater chemical data from Southwestern Oklahoma from the 1950's up to the present suggests that dedolomitization has occurred throughout this time period in evaporite sequences in Southwestern Oklahoma. Reports from groundwater well logs in the region of vein calcite suggest secondary precipitation, an observation in accord with dedolomite formation In terms of the amounts of void space produced by dissolution, dedolomitization can dominate gypsum dissolution alone, especially in periods of quiescent aquifer recharge when gypsum-water systems would have otherwise equilibrated and karst development ceased. Mass balance modeling plus molar volume considerations show that for every cubic cm of original rock (dolomite plus gypsum), there is 0.54 cm(3) of calcite and 0.47 cm(3) of void space produced Only slightly more pore space results if the dedolomitization reaction proceeds by psuedomorphic replacement of dolomite by calcite than in a reaction mechanism based on conservation of bicarbonate

An overview of the geology of the Transvaal Supergroup dolomites (South Africa), 1998,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Eriksson Pg, Altermann W,
In the Neoarchaean intracratonic basin of the Kaapvaal craton, between approximately 2640 Ma and 2516 Ma, two successive stromatolitic carbonate platforms developed. Deposition started with the Schmidtsdrif Subgroup, which is probably oldest in the southwestern part of the basin, and which contains stromatolitic carbonates, siliciclastic sediments and minor lava flows. Subsequently, the Nauga formation carbonates were deposited on peritidal flats located to the southwest and were drowned during a transgression of the Transvaal Supergroup epeiric sea, around 2550 Ma ago. This transgression led to the development of a carbonate platform in the areas of the preserved Transvaal and Griqualand West basins, which persisted for 30-50 Ma. During this time, shales were deposited over the Nauga Formation carbonates in the south-western portion of the epeiric sea. S subsequent period of basin subsidence led to drowning of the stromatolitic platform and to sedimentation of chemical, iron-rich silica precipitates of the banded iron formations (BIF) over the entire basin. Carbonate precipitation in the Archaean was largely due to chemical and lesser biogenic processes, with stromatolites and ocean water composition playing an important role. The stromatolitic carbonates in the preserved Griqualand West and Transvaal basins are subdivided into several formations, based on the depositional facies, reflected by stromatolite morphology, and on a intraformational unconformities; interbedded tuffs and available radiometric age data do not ye permit detailed correlation of units from the two basins. Thorough dolomitisation of most formations took place at different post-depositional stages, but mainly during early diagenesis. Partial silification was the result of diagenetic and weathering processes. Karstification of the carbonate rocks was related to periods of exposure to subaerial conditions and to percolation of groundwater. Such periods occurred locally at the time of carbonate and BIF deposition. Main karstification, however, probably took place during an erosional period between approximately 2430 Ma and 2320 Ma

Processes controlling colloid composition in a fractured and karstic aquifer in eastern Tennessee, USA, 1998,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Mccarthy J. F. , Shevenell L. ,
Groundwater was sampled from a number of wells along recharge pathways between fractured shale and karstic formations to evaluate the chemical and hydrologic mechanisms controlling the nature and abundance of groundwater colloids. The colloids recovered using low flow rate purging and sampling exhibited a composition and abundance consistent with lithology, flow paths, and effects of hydrology and aqueous chemistry on colloid mobilization and stability. In general, the larger-size colloids and Ca-containing colloids were more abundant in the karstic lithologies, while Na-containing colloids were more important in the shales. The composition of the colloids reflected recharge pathways from the fractured shale and dolomite formations on the ridges into the limestone in the valley floor. The Mg-colloids in the limestone reflect the possible contributions from the dolomite, while the Na, K, and Si reflect possible contributions from the shale, However, it was not possible to use the colloid composition as a signature to demonstrate colloid transport from one lithology to another. Mixing of recharge water from the shale with groundwater within the limestone formation and precipitation/dissolution reactions could account for the colloids present in the limestone without invoking transport of specific shale-derived colloids into the limestone formation. The abundance of colloids in groundwater appears to be controlled by both chemical factors affecting colloid stability, as well as physical factors related to hydrology (storm-driven recharge and water velocities). In general, colloids were more abundant in wells with low ionic strength, such as shallow wells in water table aquifers near sources of recharge at the top of the ridges, Increases in cation concentrations due to dissolution reactions along Bow paths were associated with decreases in colloid abundance. However, in spite of elevated ionic strength, colloid concentrations tended to be unexpectedly high in karstic wells that were completed in cavities or water-bearing fractures. The higher levels of colloids appear to be related to storm-driven changes in chemistry or flow rates that causes resuspension of colloids settled within cavities and fractures. Published by Elsevier Science B.V

Organic matter in the Upper Silesian (Mississippi Valley-type) Zn-Pb deposits, Poland, 1999,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Sassgustkiewicz M. , Kwiecinska B. ,
Organic matter contained in large amounts in the Upper Silesian Zn-Pb ore deposits has been identified as dopplerite-calcium humate. This humic, amorphous substance was precipitated from humic acids by calcium ion loading. The precipitation of dopplerite was contemporaneous with sulfide deposition at the time of initial and mature karst processes. The hydrothermal karst dissolution supplied calcium ions but the source of humic acids is still conjectural. The geochemical data indicate that the most probable source for the organic matter deposited in the Zn-Pb ores are overlying Triassic Keuper shales containing dispersed humic organic substance

Pre-Devonian landscape of the Baltic Oil-Shale Basin, NW of the Russian Platform, 1999,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Puura Vaino, Vaher Rein, Tuuling Igor,
The erosional relief of Ordovician and Silurian deposits in Estonia was developed during the continental period in late Silurian and early-middle Devonian times. The uplift of the area and marine regression were induced by compressional tectonics in the continental interior related to the closure of the Iapetus and Tornqvist Oceans. In the northern part of the Baltic sedimentary basin (Estonia), on the gentle southerly dipping slope between the Fennoscandian Shield (Finland) and Baltic Syneclise (Latvia), a pre-Devonian, slightly rugged erosional relief with few cuesta was developed. The pre-Devonian erosional landforms -- hills, depressions and escarpments reaching 150 m in height -- were probably buried under the Devonian deposits and then partly re-exposed by pre-Quaternary erosion. These landforms are described in detail using data from several thousands of cores drilled in the course of oil-shale and phosphorite exploration and mining

Mesozoic dissolution tectonics on the West Central Shelf, UK Central North Sea, 1999,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Clark Ja, Cartwright Ja, Stewart Sa,
3-D seismic mapping of the Upper Jurassic Kimmeridge Clay Formation on the West Central Shelf in the Central North Sea reveals a complex fault array which is constrained by seismic interpretation and well control to be of late Jurassic/early Cretaceous age. Fault shapes in plan-view range from linear to circular. Linear fault lengths are 200-300 m to 5 km, the strongly curved and circular faults range in diameter from 100-1000 m. Fault trends are apparently random and display no correlation in location or trend with basement (sub-Zechstein) structures. There is, however, a strong link between this fault pattern and the structure of the top Zechstein (top salt) surface. Linear faults occur at the edges of elongate salt walls and the circular faults lie directly above structures which have been interpreted here as tall, steep-sided salt chimneys. The salt chimneys are present only in the thick, elongate minibasins of Triassic sediment which lie between the salt walls. It is argued that salt dissolution controls the timing, location, orientation and shape of the late Jurassic/early Cretaceous faults. A model is provided to account for the development of both salt walls and chimneys. We suggest that early Triassic karstification of the Zechstein evaporites led to development of an array of circular collapse features. During the ensuing episode of Triassic halokinesis which led to minibasin subsidence and salt wall growth, salt passively 'intruded' the circular collapse features within the subsiding minibasins to form narrow salt chimneys. The resulting array of salt walls and chimneys was subject to dissolution during subsequent subaerial exposure and the late Jurassic marine transgression of the basin (creating the observed fault array), prior to sealing of the salt from circulating groundwater by compaction of the Upper Jurassic and Lower Cretaceous shales which blanket the area. (C) 1999 Elsevier Science Ltd. All rights reserved

Phnomnes de karstification observs dans une cavit artificielle du Rincn Blanco (Argentine), 2000,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Barredo, Silviap.
The Rincon Blanco subbasin is located in San Juan Province, Argentina, between 69 15' west by 314' to 31 33' south and is characterised by a non marine continental infilling. During the Tertiary times it underwent compressional deformation folding it into a tight north-_south trending syncline. The whole sedimentary sequence is comprised of coarse-grained units interfingered with sandstones and shales. In particular, these latter were deposited in an alkaline lake and are composed of carbonate and organic rich strata. These characteristic lacustrine facies bear bituminous shales widely known as "Rincon Blanco oil slates". During the 1950' s and 1970' s, they were densely explored resulting in a number of galleries that presently are abandoned. They were cut in the bituminous rocks exposing west-east and southeast-northwest systems of minor faults and local fractures. These discontinuities permitted the inflow of meteoric waters through the overlying layers and into these artificial caves, thus resulting in carbonate cement dissolution, and, re-precipitation as tiny stalactites, stalagmites, thick travertine deposits in the floor with incipient microchannels accompanied by pools (gurs) with pearls and botroidal-like concretions. Several solutional speleothems are also found and correspond to ceiling and wall pockets and floor pits. This phenomena seemed to be related to acidic water coming from small discharges and flowing through the network of integrated tectonic openings to the innermost tunnel sections where humid air reaches saturation. Water trickling resulting from condensation produces erosional features and, together with dropping and occasional flows, the speleothems. Events of slight flow turbulence in some enlarged fractures are also inferred by the presence of ceiling and floor dissolutional features.

Vein and Karst Barite Deposits in the Western Jebilet of Morocco: Fluid Inclusion and Isotope (S, O, Sr) Evidence for Regional Fluid Mixing Related to Central Atlantic Rifting, 2000,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Valenza Katia, Moritz Robert, Mouttaqi Abdellah, Fontignie Denis, Sharp Zachary,
Numerous vein and karst barite deposits are hosted by Hercynian basement and Triassic rocks of the western Jebilet in Morocco. Sulfur, oxygen, and strontium isotope analyses of barite, combined with fluid inclusion microthermometry on barite, quartz, and calcite were used to reveal the nature and source of the ore-forming fluids and constrain the age of mineralization. The{delta} 34S values of barite between 8.9 and 14.7 per mil are intermediate between the sulfur isotope signatures of Triassic evaporites and Triassic-Jurassic seawater and lighter [IMG]f1.gif' BORDER='0'>, probably derived from the oxidation of dissolved H2S and leaching of sulfides in the Hercynian basement. The 87Sr/86Sr ratios of barite between 0.7093 and 0.7130 range between the radiogenic strontium isotope compositions of micaceous shale and sandstone and the nonradiogenic isotopic signature of Triassic to Jurassic seawater and Cambrian limestone. The{delta} 18O values of barite between 11 and 15 per mil (SMOW) support mixing between two or more fluids, including Late Triassic to Jurassic seawater or a water dissolving Triassic evaporites along its flow path, hot basinal, or metamorphic fluids with{delta} 18O values higher than 0 per mil and/or meteoric fluids with{delta} 18O values lower than 0 per mil. The general trend of decreasing homogenization temperatures and initial ice melting temperatures with increasing salinities of H2O-NaCl {} CaCl2 fluid inclusions trapped in barite, quartz, and calcite indicates that a deep and hot basinal fluid with salinities lower than 6 wt percent NaCl equiv might have mixed with a cooler surficial solution with a mean salinity of 20 wt percent NaCl equiv. Calcium was leached from the Cambrian limestone and the clastic and mafic volcanic rocks of the Hercynian basement. Alkali feldspars and micas contained in the Cambrain sandstones provided most of the Ba to the hydrothermal system. Vein and karst deposits are modeled as a two-component mixing process in which the temperature and the S and Sr isotope composition of the end members changed during the 220 to 155 Ma interval. The hot basinal fluid remained volumetrically dominant during the entire mineralization process. Differences in mean S, O, and Sr isotope compositions among the barite families are interpreted as reflecting differences in mineralization age. Most barite deposits formed before the Kimmeridgian, except for north-south-oriented vein barite, karst barite, and barite cement in the conglomeratic Upper Jurassic, which were deposited later, possibly around 155 Ma. Similar genetic processes have been described for late Paleozoic to Mesozoic F-Ba vein deposits in western Europe. The vein and karst barite in the western Jebilet of Morocco reveals a wide-scale regional mineralization event related to Central Atlantic rifting

Diagenetic History of Pipe Creek Jr. Reef, Silurian, North-Central Indiana, U.S.A, 2000,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Simo J. A. , Lehmann Patrick J. ,
Calcite cements in the Silurian (Ludlovian) Pipe Creek Jr. Reef, north-central Indiana, are compositionally zoned with characteristic minor-element concentrations and stable-isotope signatures, and were precipitated in different diagenetic environments. Superposition and crosscutting relationships allow us to group cement zones and to relate them to the sequence stratigraphic evolution of the reef. Pipe Creek Jr. Reef grew in normal marine waters, with the reef top high (greater than 50 m) above the platform floor. Flank facies are volumetrically important and are preserved largely as limestone, in contrast to most dolomitized Silurian reefs in the midcontinent. Syndepositional marine cements fill primary porosity and synsedimentary fractures and are interlayered with marine internal sediment. Now low-magnesium calcite, their isotopic compositions are similar to those of depositional grains and cements estimated to have precipitated from Ludlovian sea waters. Depositional porosity was reduced by 75% by the precipitation of these syndepositional cements, which stabilized the steeply dipping flank slope. Postdepositional, clear calcite cements are interpreted as shallow-phreatic and burial cements on the basis of their relationship to periods of karstification and fracturing. Shallow-phreatic cements, with concentric cathodoluminescent (CL) zonation, precipitated in primary pores and are postdated by fractures and caves filled with Middle Devonian sandstone. CL zonal boundaries are sharp, and some, near a major stratigraphic unconformity, show evidence of dissolution. The volumetric abundance of the individual CL zones varies in the reef, indicating a complex superposition of waters of varying chemistry and rock-water interaction that are probably related to relative sea-level changes. This important aspect of the reef stratigraphy is recorded only by the diagenetic succession, because evidence of earlier sea-level changes is removed by a major later regional unconformity. Burial cements are the youngest diagenetic feature recognized, and they rest conformably or unconformably over older cements. They exhibit both concentric CL zonation and sectoral zoning, they are ferroan to nonferroan, and they contain thin sulfide zones along growth-band boundaries. Their isotopic compositions do not overlap with shallow-phreatic or marine cement values. Degraded oil postdates burial cements, and is composed of the same sterane class as the Devonian-age Antrim Shale, the probable source rock. This source contrasts with that of reef reservoirs in the Michigan Basin, where Silurian strata are commonly the hydrocarbon source

Dolomitization and Dolomite Neomorphism: Trenton and Black River Limestones (Middle Ordovician) Northern Indiana, U.S.A, 2000,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Yoo Chan Min, Gregg Jay M. , Shelton Kevin L. ,
The Trenton and Black River Limestones are dolomitized extensively along the axis of the Kankakee Arch in Indiana, with the proportion of dolomite decreasing to the south and southeast of the arch. Planar and nonplanar dolomite replacement textures and rhombic (type 1) and saddle (type 2) void-filling dolomite cements are present. Three stages of dolomitization, involving different fluids, are inferred on the basis of petrographic and geochemical characteristics of the dolomites. Nonferroan planar dolomite has relatively high {delta}18O values (-1.8 to -6.1{per thousand} PDB) and has 87Sr/86Sr ratios (0.70833 to 0.70856) that overlap those of Middle Ordovician seawater. Petrography, geochemistry, and the geometry of the dolomitized body suggest that the planar dolomite was formed in Middle and Late Ordovician seawater during the deposition of the overlying Maquoketa Shale. Ferroan planar and nonplanar dolomite occurs in the upper few meters of the Trenton Limestone, confined to areas underlain by planar dolomite. This dolomite contains patches of nonferroan dolomite with cathodoluminescence (CL) characteristics similar to underlying planar dolomite. Ferroan dolomite has relatively low {delta}18O values (-5.1 to -7.3{per thousand} PDB) and has slightly radiogenic 87Sr/86Sr ratios (0.70915 to 0.70969) similar to those obtained for the overlying Maquoketa Shale. These data indicate that ferroan dolomite formed by neomorphism of nonferroan planar dolomite as fluids were expelled from the overlying Maquoketa Shale during burial. The absence of ferroan dolomite at the Trenton-Maquoketa contact, in areas where the earlier-formed nonferroan planar dolomite also is absent, indicates that the fluid expelled from the overlying shale did not contain enough Mg2 to dolomitize limestone. Type 1 dolomite cement has isotopic compositions similar to those of the ferroan dolomite, suggesting that it also formed from shale-derived burial fluids. CL growth zoning patterns in these cements suggest that diagenetic fluids moved stratigraphically downward and toward the southeast along the axis of the Kankakee Arch. Type 2 saddle dolomite cements precipitated late; their low {delta}18O values (-6.0 to -7.0{per thousand} PDB) are similar to those of the type 1 dolomite cement. However, fluid-inclusion data indicate that the saddle dolomite was precipitated from more saline, basinal fluids and at higher temperatures (94{degrees} to 143{degrees}C) than the type 1 cements (80{degrees} to 104{degrees}C). A trend of decreasing fluid-inclusion homogenization temperatures and salinities from the Michigan Basin to the axis of Kankakee Arch suggests that these fluids emerged from the Michigan Basin after precipitation of type 1 cement

Hydrologic analysis of discharge sustainability from an abandoned underground coal mine, 2000,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/ on line 943
Burbey Tj, Younos T, Anderson Et,
Discharge from flooded abandoned subsurface coal mines is considered a potential source for water supplies where other acceptable water sources are not available. The objective of this study was to develop procedures for determining sustainability of mine-water discharge using rainfall and discharge data for a case study site. The study site is located in southwest Virginia where Late Paleozoic sequences of sandstone, coal, and shale predominate. A rain gauge and a flow rate monitoring system were installed at the site and data were collected for a period of 100 days. The recording period corresponded with one of the driest periods in recent years and, therefore, provided valuable information regarding the flow sustainability during baseflow conditions. From available data on underground mining patterns, geology, and ground water flow regimes, it was determined that a coal mine aquifer exhibits hydraulic characteristics very similar to the extremely heterogeneous systems observed in karst aquifers, and the mine discharge is analogous to springflow. Thus, techniques commonly used in karst-water systems and springflow analysis were used to develop rainfall/mine-discharge relationships. Springflow recession analysis was performed on five rainfall recessions and the coefficient for each recession was compared and interpreted in light of known geologic information. It was found that the recession coefficients described the mine discharge adequately and the mine aquifer response to a rainfall pulse was very similar to the response from certain ts;pes of karst aquifers. A cross-correlation analysis was performed to verify the results of the recession analysis and to develop a 'black box' statistical model for discharge data. The correlation analysis proved the validity of springflow recession analysis for mine discharge. The recorded data length was not adequate to create a statistical model, however, but a procedure was proposed for a statistical model that could be used with large flow records. For the study site, the mine discharge was found to be sustainable for a prolonged period of time

Results 16 to 30 of 78
You probably didn't submit anything to search for