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Enviroscan Ukrainian Institute of Speleology and Karstology

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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 alluvial plain is a plain formed by the deposition of water borne sediments [16].?

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

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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;
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Your search for petroleum (Keyword) returned 48 results for the whole karstbase:
Showing 31 to 45 of 48
Australian Zn-Pb-Ag Ore-Forming Systems: A Review and Analysis, 2006,
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Huston David L. , Stevens Barney, Southgate Peter N. , Muhling Peter, Wyborn Lesley,
Zn-Pb-Ag mineral deposits are the products of hydrothermal ore-forming systems, which are restricted in time and space. In Australia, these deposits formed during three main periods at ~2.95, 1.69 to 1.58, and 0.50 to 0.35 Ga. The 1.69 to 1.58 Ga event, which accounts for over 65 percent of Australia's Zn, was triggered by accretion and rifting along the southern margin of Rodinia. Over 93 percent of Australia's Zn-Pb-Ag resources were produced by four ore-forming system types: Mount Isa (56% of Zn), Broken Hill (19%), volcanic-hosted massive sulfide (VHMS; 12%), and Mississippi Valley (8%). Moreover, just 4 percent of Australia's land mass produced over 80 percent of its Zn. The four main types of ore-forming systems can be divided into two 'clans,' based on fluid composition, temperature, and redox state. The Broken Hill- and VHMS-type deposits formed from high-temperature (>200{degrees}C) reduced fluids, whereas the Mount Isa- and Mississippi Valley-type deposits formed from low-temperature (<200{degrees}C), H2S-poor, and/or oxidized fluids. The tectonic setting and composition of the basins that host the ore-forming systems determine these fluid compositions and, therefore, the mineralization style. Basins that produce higher temperature fluids form in active tectonic environments, generally rifts, where high heat flow produced by magmatism drives convective fluid circulation. These basins are dominated by immature siliciclastic and volcanic rocks with a high overall abundance of Fe2. The high temperature of the convective fluids combined with the abundance of Fe2 in the basin allow inorganic sulfate reduction and leaching of sulfide from the country rock, producing reduced, H2S-rich fluids. Basins that produce low-temperature fluids are tectonically less active, generally intracratonic, extensional basins dominated by carbonate and variably mature siliciclastic facies with a relatively low Fe2 abundance. In these basins, sediment maturity depends on the paleogeography and stratigraphic position in an accommodation cycle. Volcanic units, if present, occur in the basal parts of the basins. Because these basins have relatively low heat flow, convective fluid flow is less important, and fluid migration is dominated by expulsion of basinal brines in response to local and/or regional tectonic events. Low temperatures and the lack of Fe2 prevent in-organic sulfate reduction during regional fluid flow, producing H2S-poor fluids that are commonly oxidized (i.e., {sum}SO4 > {sum}H2S). Fluid flow in the two basin types produces contrasting regional alteration systems. High-temperature fluid-rock reactions in siliciclastic-volcanic-dominated basins produce semiconformable albite-hematite-epidote assemblages, but low-temperature reactions in carbonate-siliciclastic-dominated basins produce regional K-feldspar-hematite assemblages. The difference in feldspar mineralogy is mostly a function of temperature. In both basin types, regional alteration zones have lost, and probably were the source of, Zn and Pb. The contrasting fluid types require different depositional mechanisms and traps to accumulate metals. The higher temperature, reduced VHMS- and Broken Hill-type fluids deposit metals as a consequence of mixing with cold seawater. Mineralization occurs at or near the sea floor, with trapping efficiencies enhanced by sub-surface replacement or deposition in a brine pool. In contrast, the low-temperature, oxidized Mount Isa- and Mississippi Valley-type fluids precipitate metals through thermochemical sulfate reduction facilitated by hydrocarbons or organic matter. This process can occur at depth in the rock pile, for instance in failed petroleum traps, or just below the sea floor in pyritic, organic-rich muds

Outcrop analog for TrentonBlack River hydrothermal dolomite reservoirs, Mohawk Valley, New York , 2006,
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Slater B. E. , Smith Jr. L. B.

Geochemical analysis and field relations of linear dolomite bodies occurring in outcrop in the Mohawk Valley of New York suggest that the area has undergone a significant faultrelated hydrothermal alteration. The dolomite occurs in the Lower Ordovician Tribes Hill Formation, which is regionally a Lower Ordovician shaley limestone with patchy dolomitization. The outcrop has an en echelon fault, fracture, and fold pattern. A three-dimensional (3-D) ground-penetrating radar (GPR) survey of the quarry floor has helped to map out faults, fractures, anticlines, synclines, and the extent of dolomitization. Most of the dolomitization occurs in fault-bounded synclines or sags flanked by anticlines. The dolomite structures are highly localized, occurring around faults, and are absent away from the faults and fractures. Trenches cut across the outcrop help relate offset along faults to the overall geometry of the dolomitized bodies. Geochemical analysis, although helpful in characterizing the conditions of dolomitization, does not define its origin absolutely. This study uses fluid inclusions, stable isotopes, 3-D GPR, core analysis, and surficial observations, which all show a link between faulting, dolomitization, and other hydrothermal alteration. Although the outcrop is much too small and shallow to act as a producing gas field, it serves as a scaled analog for the Trenton–Black River hydrothermal dolomite reservoirs of eastern United States. It may therefore be studied to help petroleum geologists characterize existing gas plays and prospect future areas of exploration.

Cave Geology, 2007,
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Palmer A. N.
Cave Geology is the definitive book on the subject by an internationally recognized authority. It can be easily understood by non-scientists but also covers a wide range of topics in enough detail to be used by advanced researchers. Illustrated with more than 500 black-and-white photographs and 250 diagrams and maps, this book is dedicated to anyone with an interest in caves and their origin. Topics include: CONTENTS Preface 1 Speleology the science of caves Cave types Cave exploring Nationwide speleological organizations Searching for caves Cave mapping Preparation of a cave map Cave science Underground photography Show caves Cave preservation and stewardship 2 Cave country Geologic time Landscape development Surface karst features Paleoleokarst Pseudokarst The scale of karst features Distribution of karst and caves The longest and deepest known caves 3 Cavernous rocks Rock types Soils and sediments Stratigraphy Highly soluble rocks Rock structure Rock and mineral analysis A brief guide to rock identification 4 Underground water in karst Types of underground water Vadose flow patterns Phreatic flow patterns Aquifers Nature of the karst water table The freshwater-seawater interface Groundwater hydraulics Flow measurements Use of flow equations in cave interpretation Measuring the flow of springs and streams Groundwater tracing Interpreting groundwater character from tracer tests and flood pulses Quantitative dye tracing 5 Chemistry of karst water Simple dissolution Dissoltion of limestone and dolomite How much rock has dissolved? pH Undersaturation and supersaturation Epigenic and hypogenic acids Chemical interactions Dissolution rates Dissolution of poorly soluble rocks Microbial effects on chemistry Isotopes and their use Analysis of spring chemistry A chemical cave tour Chemical field studies 6 Characteristics of solution caves Cave entrances Passage types Passage terminations Cave rooms Cave levels Cave patterns Minor solution features in caves Interpreting flow from scallops Cave sediments Bedrock collapse Cave biology 7 Speleogenesis: the origin of caves Basic concepts Development of ideas about cave origin Comprehensive views of cave origin Rates of cave enlargement Insight from computer modeling Life cycle of a solution cave 8 Control of cave patterns by groundwater recharge Sinkhole recharge: branchwork caves The problem of maze caves Floodwater caves Caves formed by diffuse flow Hypogenic caves Polygenetic caves Influence of climate 9 Influence of geology on cave patterns Distribution of soluble rocks Influence of rock type Influence of geologic structure Relation of caves to landscape evolution A guide to cave patterns 10 Cave minerals Origin and growth of cave minerals Origin of common cave minerals Speleothem types Speleothem growth rates Speleothem decay 11 Caves in volcanic rocks Volcanic processes and landscapes Types of lava caves Origin and character of lava-tube caves Speleogens and speleothems in lava caves Time scale of lava caves 12 Cave meteorology and internal weathering Composition of cave air Cave temperatures Air movement Evaporation and condensation Weathering in the cave atmosphere Chemical zones in air-filled caves 13 Caves and time Relative and numerical ages Determining cave ages Studies of past climates Caves through the ages 14 Geologic studies of caves Field mapping Calibrating survey instruments Geologic interpretions Testing interpretations for validity Detailed analysis of a cave Further goals 15 Application of cave geology to other geosciences The problem of sampling bias Water supply Engineering applications Land management Interpretation of geologic processes Petroleum geology Mining Scientific frontiers The limits of discovery Glossary References Index Conversion between U.S. and metric units

Structurally complex reservoirs: an introduction, 2007,
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Jolley S. J. , Barr D. , Walsh J. J. , Knipe R. J.

Structurally complex reservoirs form a distinct class of reservoir, in which fault arrays  and fracture networks, in particular, exert an over-riding control on petroleum trapping and production  behaviour. With modern exploration and production portfolios commonly held in geologically  complex settings, there is an increasing technical challenge to find new prospects and to  extract remaining hydrocarbons from these more structurally complex reservoirs. Improved  analytical and modelling techniques will enhance our ability to locate connected hydrocarbon  volumes and unswept sections of reservoir, and thus help optimize field development, production  rates and ultimate recovery. This volume reviews our current understanding and ability to model the  complex distribution and behaviour of fault and fracture networks, highlighting their fluid compartmentalizing  effects and storage-transmissivity characteristics, and outlining approaches for predicting  the dynamic fluid flow and geomechanical behaviour of structurally complex reservoirs.  This introductory paper provides an overview of the research status on structurally complex reservoirs  and aims to create a context for the collection of papers presented in this volume and, in doing  so, an entry point for the reader into the subject. We have focused on the recent progress and outstanding  issues in the areas of: (i) structural complexity and fault geometry; (ii) the detection and  prediction of faults and fractures; (iii) the compartmentalizing effects of fault systems and complex  siliciclastic reservoirs; and (iv) the critical controls that affect fractured reservoirs.

Paleokarst reservoirs and gas accumulation in the Jingbian field, Ordos Basin, 2008,
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Li J. , Zhang W. , Luo X. , Hu G.

The Jingbian gas field in central Ordos Basin, with a proven initial in place gas reserve of approximately 11 trillion cubic meters, is the largest paleokarst carbonate gas field in China. Paleokarst in Ordovician strata of central Ordos most commonly occurs in the paleoweathering surface of the O1m5 member of the Majiagou Formation. The karst intervals are generally proximal to the sub-Upper Paleozoic unconformity; however, dissolution features in strata well below that exposure surface are possibly related to intra-Majiagou Formation unconformities. The quality of gas reservoirs are initially controlled by sedimentary facies, with anhydrite-bearing dolomite flat facies being the most favorable zones for dissolution and dolomitization to form karst and large/small dissolution cavities. The gases are generally dry, derived dominantly from the overlying Carboniferous–Permian coal measures. The gases are accumulated in stratigraphic traps related to karst paleo-geomorphology and lithologic traps associated with late diagenetic features of carbonate rocks. Although the precise timings of the thermal events during the evolution of the Ordos Basin are still subject to considerable debate, there is a general consensus that events occurring during the Yenshanian orogeny (150–115 Ma) were the most important for the Paleozoic source rocks. It appears that two episodes of hydrocarbon charge have occurred in the Ordovician gas reservoirs in the Jingbian field.  

Fluid flow reconstruction in karstified Panormide platform limestones (north-central Sicily): Implications for hydrocarbon prospectivity in the Sicilian fold and thrust belt, 2010,
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Dewever B. , Berwouts I. , Swennen R. , Breesch L. , Ellam R. M.

Diagenetic analysis based on field and petrographic observations, isotope and microthermometric data was used to reconstruct the fluid flow history of the Cretaceous shallow water limestones from the Panormide platform exposed in north-central Sicily. Analysis focused on diagenetic products in cavities and dissolution enlarged fractures of the karstified limestones that occur just below a regional unconformity. The fluid flow history could be broken down into five stages that were linked to the kinematic and burial history of the region. (1) Petrography (zoned cathodoluminescence and speleothem textures) and stable isotopes (6.5 PDB &/Tm_2 to _5 _C), but at increasingly higher temperatures (Th 60–120 _C). This has been interpreted as precipitation during Oligocene foredeep burial. (4) Hot (Th 130–180 _C), low saline (Tm he low salinity and relatively high d18OSMOW signatures of the fluids are interpreted to be the result of clay dewatering reactions. The presence of bitumen and associated fluorite with hydrocarbon inclusions at this stage in the paragenesis constrains the timing of oil migration in the region. (5) Finally, high saline fluids with elevated 87Sr/86Sr (0.7095–0.7105) signatures invaded the karst system. This last fluid flow event was possibly coeval with localized dolomitization and calcite cementation along high-angle faults of Pliocene age, as suggested by identical radiogenic signatures of these diagenetic products.

Imprints of hydrocarbon-bearing basinal fluids on a karst system: mineralogical and fluid inclusion studies from the Buda Hills, Hungary, 2011,
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Poros Zsofia, Mindszenty Andrea, Molnar Ferenc, Pironon Jacques, Gyori Orsolya, Ronchi Paola, Szekeres Zoltan

Calcite veins and related sulphate–sulphide mineralisation are common in the Buda Hills. Also, abundant hypogenic caves are found along fractures filled with these minerals pointing to the fact that young cave-forming fluids migrated along the same fractures as the older mineralising fluids did. The studied vein-filling paragenesis consists of calcite, barite, fluorite and sulphides. The strike of fractures is consistent—NNW–SSE—concluding a latest Early Miocene maximum age for the formation of fracture-filling minerals. Calcite crystals contain coeval primary, hydrocarbon-bearing- and aqueous inclusions indicating that also hydrocarbons have migrated together with the mineralising fluids. Hydrocarbon inclusions are described here for the first time from the Buda Hills. Mixed inclusions, i.e., petroleum with ‘water-tail’, were also detected, indicating that transcrystalline water migration took place. The coexistence of aqueous and petroleum 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 hydrocarbon-bearing fluids were diluted by regional karst water. FT-IR investigations revealed that CO2 and CH4 are associated with hydrocarbons. Groundwater also contains small amounts of HC and related gases on the basin side even today. Based on the location of the paleo- and recent hydrocarbon indications, identical migration pathways were reconstructed for both systems. Hydrocarbon-bearing fluids are supposed to have migrated north-westward from the basin east to the Buda Hills from the Miocene on.

Formation and accumulation of oil and gas in marine carbonate sequences in Chinese sedimentary basins, 2011,
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Jin, Z.

Advances in studies of formation and accumulation mechanisms of oil and gas in marine carbonate sequences have led to continuing breakthroughs of petroleum exploration in marine carbonate sequences in Chinese sedimentary basins in recent years. The recently discovered giant Tahe Oil Field and Puguang Gas Field have provided geological entities for further studies of the formation and accumulation of oil and gas in marine carbonate sequences. Marine carbonate sequences in China are characterized by old age, multiple structural deformation, differential thermal evolution of source rocks, various reservoir types (i.e. reef-bank complex and paleo-weathered crust karst reservoir), uneven development of caprocks, especially gypsum seal, and multi-episodes of hydrocarbon accumulation and readjustment. As a result, the formation of hydrocarbon accumulations in the Chinese marine carbonate sequences has the following features: (i) the high-quality marine source rocks of shale and calcareous mudstone are often associated with siliceous rocks or calcareous rocks and were deposited in slope environments. They are rich in organic matter, have a higher hydrocarbon generation potential, but experienced variable thermal evolutions in different basins or different areas of the same basin. (ii) High quality reservoirs are controlled by both primary depositional environments and later modifications including diagenetic modifications, structural deformations, and fluid effects. (iii) Development of high-quality caprocks, especially gypsum seals, is the key to the formation of large- and medium-sized oil and gas fields in marine carbonate sequences. Gypsum often constitutes the caprock for most of large sized gas fields. Given that Chinese marine carbonate sequences are of old age and subject to multiple episodes of structural deformation and superposition, oil and gas tend to accumulate in the slopes and structural hinge zones, since the slopes favor the development of effective assemblage of source-reservoir-caprock, high quality source rocks, good reservoirs such as reef-bank complex, and various caprocks. As the structural hinge zones lay in the focus area of petroleum migration and experienced little structural deformation, they are also favorable places for hydrocarbon accumulation and preservation.

Paleokarst of the USA: A Brief Review, 2011,
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Palmer A. N. , Palmer M. V.

Paleokarst consists of solutional features from a prior geomorphic phase that have been preserved by  burial or by a substantial change in local environment. The two major paleokarst horizons in North  America are of Early-Middle Ordovician (post-Sauk) age and Mississippian-Pennsylvanian (post-Kaskaskia) age. There are also several less extensive paleokarst zones. They all differ in detail but  typically include remnants of surface karst features, caves, breccias, hypogenic porosity, and related  mineral suites. In places they provide high-permeability zones significant to water supply, or serve as  hosts to petroleum, ores, and later karst development. Studies of paleokarst give significant evidence for  past geologic and hydrologic conditions, both surficial and deep seated.

Sulfuric Acid Caves, 2012,
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Palmer A, Hill C.

Most caves owe their origin to carbonic acid generated in the soil. In contrast, sulfuric acid caves are produced by the oxidation of sulfides beneath the surface. Although sulfuric acid caves are relatively few, they include some large and well-known examples, such as Carlsbad Cavern, New Mexico. They also provide evidence for a variety of deep-seated processes that are important to petroleum geology, ore geology, tectonic history, and the nascent field of karst geomicrobiology.

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Florea Lee J.


This manuscript offers preliminary geochemical evidence that investigates the potential for hypogene speleogenesis in the Cumberland Plateau of southeastern Kentucky, U.S.A. The region was traditionally considered a classic example of epigenic karst, but new insights have uncovered tantalizing observations that suggest alternatives to simple carbonic acid speleogenesis. Such first-order observations have included natural petroleum seeps at the surface and in caves, occasional cave morphologies consistent with action of hypogene fluids, and prolific gypsum within cave passages. To this point, geochemical data from caves and springs verify carbonic acid as the primary dissolutional agent; however, these same analyses cannot rule out sulfuric acid as a secondary source of dissolution. In this paper, Principal Component Analysis of ionic data reveals two components that coordinate with parameters associated with “karst water” and shallow brine. In contrast, molar ratios of Ca+ and Mg+ as compared to HCO3 - and SO4 2- closely follow the reaction pathway stipulated by the carbonate equilibria reactions. Despite these data, the role, if any, of hypogene speleogenesis in the karst of the Cumberland Plateau remains inconclusive. It is very likely that carbonic acid dominates speleogenesis; however, contributions from sulfuric acid may influence our understanding of “inception” and carbon flux within these aquifers.

Deep hydrogeology: a discussion of issues and research needs, 2013,
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Tsang Chinfu, Niemi Auli

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

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Duchene, H. R.

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Johnson, K. S.

Permian bedded salt is widespread in the Anadarko Basin of western Oklahoma and the Texas Panhandle, where partial or total dissolution of the shallowest salt in some areas has resulted in subsidence and/or collapse of overlying strata. Groundwater has locally dissolved these salts at depths of 10–250 m. The distribution (presence or absence) of salt-bearing units, typically 80–150 m thick, is confirmed by interpretation of geophysical logs of many petroleum tests and a few scattered cores. Salt dissolution by ground water is referred to as “salt karst.”Chaotic structures, collapse features, breccia pipes, and other evidence of disturbed bedding are present in Permian, Cretaceous, and Tertiary strata that overly areas of salt karst. The dip of Permian and post-Permian strata in the region normally is less than one degree, mainly towards the axis of the Anadarko Basin. Where strata locally dip in various directions at angles of 5–25 degrees or more, and underlying salt units show clear evidence of dissolution, these chaotic dips must result (mostly, if not totally) from subsidence and collapse into underlying salt-dissolution cavities.Gypsum karst and resultant collapse of overlying strata have been proposed in many parts of the Anadarko Basin. However, the gypsum beds typically are only 1–6 m thick and more than 100 m deep, and cannot contribute to disruption of outcropping strata—except where they are within 10–20 m of the surface.Typical areas of disturbed bedding comprise several hectares, or more, with outcrops of moderately dipping strata—as though large blocks of rock have foundered and subsided into large underground cavities. Other examples of disturbed bedding are small-diameter breccia pipes, or chimneys, that extend vertically up from salt-karst cavities, through several hundred meters of overlying strata. The best evidence of these chimneys are collapsed blocks of Cretaceous strata, chaotically dropped some 50 m, or more, that are now juxtaposed against various Permian formations on the north flank of the Anadarko Basin. Any study of surface or shallow-subsurface geology in the Anadarko Basin must consider the influence of subsurface salt karst on the structure and distribution of overlying rocks

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Johnson K. S. , Wilkerson J. M.

Cedar Ridge Dam and Reservoir will be built to supply water for the city of Abilene, Texas. The original damsite (CR) was to be located on Clear Fork of Brazos River in Throckmorton County, but initial coring of the damsite encountered unsuspected gypsum beds in the Permian-age Jagger Bend/Valera Formation. Gypsum is a highly soluble rock that typically contains karst features, and its presence in a dam foundation or impoundment area could allow water to escape from the reservoir. A decision was made to look at potential sites farther upstream (to the southwest), where west-dipping gypsum beds would be deeper underground and karst problems would be minimized or eliminated.The first phase of the relocation was a comprehensive field study of Clear Fork Valley, upstream of the original damsite, to identify gypsum outcrops; gypsum was exposed at only one location, just above damsite CR. The second phase of the study was examination of nearly 100 petroleum-test geophysical logs to identify, correlate, and map the subsurface gypsum and associated rock layers upstream of the original damsite. The gypsiferous sequence is 30–45 m thick, and consists of 8 gypsum beds, mostly 1–3 m thick, interbedded with red-brown and gray shale units 1–10 m thick. Gypsum beds comprise 25–30% of the gypsiferous sequence. Gypsum beds dip uniformly to the west at about 7 m/km (about 0.4 degrees), and thus the uppermost gypsum is at least 23 m beneath the newly proposed damsite (A), about 8 km to the southwest.Subsequent coring and other studies of the new damsite A confirm that gypsum beds are 23 m beneath the newly proposed dam. There is no evidence of solution channels or other karst features beneath this site, and thus there is little likelihood of water loss from the reservoir at the new site due to gypsum karst.

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