Open Access. Powered by Scholars. Published by Universities.®

Geology Commons™

Open Access. Powered by Scholars. Published by Universities.®

Discipline
Institution
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 25261 - 25290 of 29965

Full-Text Articles in Geology

Geochemical Analysis Of Ironstone Preserved Molluscan Fossils Of The Hell Creek Formation (Cretaceous) And Ludlow Member Of The Fort Union Formation (Paleogene) Of Southwestern North Dakota, Tanya P. Justham Jan 2008

Geochemical Analysis Of Ironstone Preserved Molluscan Fossils Of The Hell Creek Formation (Cretaceous) And Ludlow Member Of The Fort Union Formation (Paleogene) Of Southwestern North Dakota, Tanya P. Justham

Theses and Dissertations

The uppermost Cretaceous Hell Creek Formation and Paleocene Ludlow Member of the Fort Union Formation in easternmost Montana and western North Dakota produce ironstone preserved freshwater molluscan fossils. Ironstone preserved mollusks are associated with ironstone nodules, which have been described as composed of iron carbonate, iron oxide, or manganese oxide by various researchers. To date, the exact composition of the ironstone preservation has not been satisfactorily determined to allow agreement between researchers. Freshwater mollusk fossils, preserved as ironstone external casts, molds, and steinkerns, tend to be highly weathered. The poor preservation of the fossils has resulted in little professional interest, …


Evaluation Of Spring Flow, Bacterial Contamination, And Distribution Of Fresh Water Resources In The Vicinity Of Verrettes, Haiti, Peter Wampler, Andrew Sisson Jan 2008

Evaluation Of Spring Flow, Bacterial Contamination, And Distribution Of Fresh Water Resources In The Vicinity Of Verrettes, Haiti, Peter Wampler, Andrew Sisson

Student Summer Scholars Manuscripts

The purpose of this study was to gain a better understanding of fresh water springs used as the primary source of potable water in rural Haiti. Field data was collected during the summer of 2008 near Verrettes, Haiti, approximately 120 km north of Port au Prince. GPS locations of 29 springs were recorded within the 87 sq km study area. Two water samples at each spring were taken for bacterial analysis: one sample was submitted to a local hospital and a duplicate sample was cultured using Coliscan© Easygel© Kits. Both capped and uncapped springs were sampled to determine whether capping …


Origin And Paleoclimatic Significance Of Late Quaternary Loess In Nebraska: Evidence From Stratigraphy, Chronology, Sedimentology, And Geochemistry, Daniel R. Muhs, E. Arthur Bettis Iii, John N. Aleinikoff, John P. Mcgeehin, Jossh Beann, Gary Skipp, Brian D. Marshall, Helen M. Roberts, William C. Johnson, Rachel Benton Jan 2008

Origin And Paleoclimatic Significance Of Late Quaternary Loess In Nebraska: Evidence From Stratigraphy, Chronology, Sedimentology, And Geochemistry, Daniel R. Muhs, E. Arthur Bettis Iii, John N. Aleinikoff, John P. Mcgeehin, Jossh Beann, Gary Skipp, Brian D. Marshall, Helen M. Roberts, William C. Johnson, Rachel Benton

United States Geological Survey: Staff Publications

Loess is one of the most extensive surficial geologic deposits in mid-continental North America, particularly in the central Great Plains region of Nebraska. Last-glacial-age loess (Peoria Loess) reaches its greatest known thickness in the world in this area. New stratigraphic, geochronologic, mineralogic, and geochemical data yield information about the age and provenance of Peoria Loess, as well as evaluation of recent climate models.


Range-Wide Phylogeographic Analysis Of The Spotted Frog Complex (Rana Luteiventris And Rana Pretiosa) In Northwestern North America, W. Chris Funk, Christopher A. Pearl, Hope M. Draheim, Michael J. Adams, Thomas D. Mullins, Susan M. Haig Jan 2008

Range-Wide Phylogeographic Analysis Of The Spotted Frog Complex (Rana Luteiventris And Rana Pretiosa) In Northwestern North America, W. Chris Funk, Christopher A. Pearl, Hope M. Draheim, Michael J. Adams, Thomas D. Mullins, Susan M. Haig

United States Geological Survey: Staff Publications

The dynamic geological and climatic history of northwestern North America has made it a focal region for phylogeography. We conducted a range-wide phylogeographic analysis of the spotted frog complex (Rana luteiventris and Rana pretiosa) across its range in northwestern North America to understand its evolutionary history and the distribution of clades to inform conservation of R. pretiosa and Great Basin R. luteiventris, candidates for listing under the US Endangered Species Act. Mitochondrial DNA sequence data from a segment of the cytochrome b gene were obtained from 308 R. luteiventris and R. pretiosa from 96 sites. Phylogenetic analysis …


Management And Conservation Note: Conserving Waste Rice For Wintering Waterfowl In The Mississippi Alluvial Valley, Jennifer P. Kross, Richard M. Kaminski, Aaron T. Pearse Jan 2008

Management And Conservation Note: Conserving Waste Rice For Wintering Waterfowl In The Mississippi Alluvial Valley, Jennifer P. Kross, Richard M. Kaminski, Aaron T. Pearse

United States Geological Survey: Staff Publications

The Mississippi Alluvial Valley (MAV), USA, is an internationally important migration and wintering region for North American waterfowl (Reinecke et al. 1989). The Lower Mississippi Valley Joint Venture (LMVJV) assumes food availability is the primary factor influencing carrying capacity of wintering waterfowl in this region (Reinecke and Loesch 1996). Because much of the MAV was converted from a seasonally flooded bottomland-hardwood ecosystem to a landscape dominated by agriculture, the LMVJV has incorporated estimates of the abundance of agricultural seeds such as rice into habitat conservation plans (Reinecke et al. 1988, Fredrickson et al. 2005). Biologists designed these plans to provide …


Erupted Magma Volume Estimates At Santiaguito And Pacaya Volcanoes, Guatemala Using Digital Elevation Models , Kelly S. Durst Jan 2008

Erupted Magma Volume Estimates At Santiaguito And Pacaya Volcanoes, Guatemala Using Digital Elevation Models , Kelly S. Durst

Dissertations, Master's Theses and Master's Reports - Open

High resolution digital elevation models (DEMs) of Santiaguito and Pacaya volcanoes, Guatemala, were used to estimate volume changes and eruption rates between 1954 and 2001. The DEMs were generated from contour maps and aerial photography, which were analyzed in ArcGIS 9.0®. Because both volcanoes were growing substantially over the five decade period, they provide a good data set for exploring effective methodology for estimating volume changes. The analysis shows that the Santiaguito dome complex grew by 0.78 ± 0.07 km3 (0.52 ± 0.05 m3 s-1) over the 1954-2001 period with nearly all the growth occurring on …


Digital Processing And Data Compilation Approach For Using Remotely Sensed Imagery To Identify Geological Lineaments In Hard-Rock Terrains : An Application For Groundwater Explorations In Nicaragua , Jill N. Bruning Jan 2008

Digital Processing And Data Compilation Approach For Using Remotely Sensed Imagery To Identify Geological Lineaments In Hard-Rock Terrains : An Application For Groundwater Explorations In Nicaragua , Jill N. Bruning

Dissertations, Master's Theses and Master's Reports - Open

Sustainable yields from water wells in hard-rock aquifers are achieved when the well bore intersects fracture networks. Fracture networks are often not readily discernable at the surface. Lineament analysis using remotely sensed satellite imagery has been employed to identify surface expressions of fracturing, and a variety of image-analysis techniques have been successfully applied in “ideal” settings. An ideal setting for lineament detection is where the influences of human development, vegetation, and climatic situations are minimal and hydrogeological conditions and geologic structure are known. There is not yet a well-accepted protocol for mapping lineaments nor have different approaches been compared in …


A Multi-Tracer Study Of Saltwater Origin, Cross-Formational Flow, And The Geochemical Evolution Of Groundwater In The Southern High Plains Aquifer Along The Western Caprock Escarpment, East-Central New Mexico, Jeff Langman Jan 2008

A Multi-Tracer Study Of Saltwater Origin, Cross-Formational Flow, And The Geochemical Evolution Of Groundwater In The Southern High Plains Aquifer Along The Western Caprock Escarpment, East-Central New Mexico, Jeff Langman

Open Access Theses & Dissertations

Sustainable management of groundwater resources requires sufficient knowledge of the distribution of fresh and saline groundwater and the processes affecting saltwater intrusion that may influence the beneficial use of groundwater. A hydrogeologic investigation that coupled various chemical and isotopic tracers, including 3H/3He, 14C, δD, δ18O, 87Sr/86Sr, and δ11B, with the physical characteristics of the aquifer was conducted to determine source waters, the origin of saltwater and its influence through cross-formational flow, and water-rock interactions in the Southern High Plains aquifer along the Western Caprock Escarpment. Sub-aquifers or local flow systems are present along the Western Caprock Escarpment, and the study …


Eocene To Oligocene Provenance And Drainage In Extensional Basins Of Southwest Montana And East-Central Idaho: Evidence From Detrital Zircon Populations In The Renova Formation And Equivalent Strata, C. N. Stroup, P. K. Link, Susanne U. Janecke, C. M. Fanning, G. M. Yaxley, L. P. Beranek Jan 2008

Eocene To Oligocene Provenance And Drainage In Extensional Basins Of Southwest Montana And East-Central Idaho: Evidence From Detrital Zircon Populations In The Renova Formation And Equivalent Strata, C. N. Stroup, P. K. Link, Susanne U. Janecke, C. M. Fanning, G. M. Yaxley, L. P. Beranek

Geosciences Faculty Publications

Middle Eocene to Early Miocene sedimentary rocks in southwest Montana and east-central Idaho were deposited within an actively extending north-trending rift system (Cabbage Patch beds and Medicine Lodge beds) and a broad depositional basin on the eastern flank of this rift (Renova Formation). Distinct sediment sources for sandstones from different parts of this extensional system are identified using detrital zircon SHRIMP geochronology and LA-MC-ICPMS Hf isotope geochemistry. Sedimentary petrology independently shows strong compositional similarities among sandstones grouped by provenance. The Muddy-Grasshopper detachment system was the eastern boundary of the Paleogene rift and controlled sediment dispersal patterns. Hf isotope ratios and …


Carbon Dioxide Concentration In Air Within The Nerja Cave (Malaga, Andalusia, Spain), Cristina Liñán, Iñaki Vadillo, Francisco Carrasco Jan 2008

Carbon Dioxide Concentration In Air Within The Nerja Cave (Malaga, Andalusia, Spain), Cristina Liñán, Iñaki Vadillo, Francisco Carrasco

International Journal of Speleology

From 2001 to 2005 the CO2 concentration of the air in the interior and exterior of the Nerja Cave was studied and its relation with the air temperature and visitor number. The average annual CO2 concentration outside of the cave is 320 ppmv, whilst inside, the mean concentration increases to 525 ppmv during autumn and winter, and in the order of 750 ppmv during spring and summer. The temporal variation of CO2 content in the air of the cave is strongly influenced by its degree of natural ventilation which is, in turn, determined by the difference between …


Surface Corrosion Of An Alpine Karren Field: Recent Measures At Innerbergli (Siebenhengste, Switzerland), Philipp Häuselmann Jan 2008

Surface Corrosion Of An Alpine Karren Field: Recent Measures At Innerbergli (Siebenhengste, Switzerland), Philipp Häuselmann

International Journal of Speleology

29 year old rock paintings in the Alpine karren field of Innerbergli (Siebenhengste, Switzerland) prevented the underlying rock from corrosion, while the surface nearby was corroded. Measurement of the steps indicates an average recent corrosion rate of 0.014 (±0.007) mm/a. This denudation rate is very similar to those observed in other comparable places and with other means.


An Investigation Of Meromixis In Cave Pools, Lechuguilla Cave, New Mexico, David B. Levy Jan 2008

An Investigation Of Meromixis In Cave Pools, Lechuguilla Cave, New Mexico, David B. Levy

International Journal of Speleology

Chemical characteristics of permanent stratification in cave pools (meromixis) may provide insight into the geochemical origin and evolution of cave pool waters. The objective of this study was to test the hypothesis that some pools in Lechuguilla Cave may be subject to ectogenic meromixis, where permanent chemical stratification is induced by input of relatively saline or fresh water from an external source. However, because organic C concentrations in Lechuguilla waters are low (typically < 1 mg L-1), biogenic meromixis resulting in O2(g)-depleted subsurface waters is not expected. Four pools at various depths below ground surface (0 m) were studied: (1) …


Late Pleistocene Cryogenic Calcite Spherolites From The Malachitdom Cave (Ne Rhenish Slate Mountains, Germany): Origin, Unusual Internal Structure And Stable C-O Isotope Composition, Detlev Konrad Richter, Dana Felicitas Christine Riechelmann Jan 2008

Late Pleistocene Cryogenic Calcite Spherolites From The Malachitdom Cave (Ne Rhenish Slate Mountains, Germany): Origin, Unusual Internal Structure And Stable C-O Isotope Composition, Detlev Konrad Richter, Dana Felicitas Christine Riechelmann

International Journal of Speleology

Cryogenic calcites yielded U-series ages in the range from 15.61±0.20 ka to 14.48±0.12 ka, which is the youngest age obtained so far for this type of cryogenic cave carbonates in Europe. Most of these particles of the Malachitdom Cave (NE Brilon, Sauerland, North Rhine-Westphalia) are complex spherolites usually smaller than 1 cm. They show δ13C-values between –1 and –5 ‰ VPDB and δ18O-values ranging from –7 to –16 ‰ VPDB, the δ13C-values increase and the δ18O-values decrease from centre to border. The complex spherolites are interpreted to be formed in slowly freezing …


Epigene And Hypogene Gypsum Karst Manifestations Of The Castile Formation: Eddy County, New Mexico And Culberson County, Texas, Usa, Kevin W. Stafford, Raymond Nance, Laura Rosales-Lagarde, Penelope J. Boston Jan 2008

Epigene And Hypogene Gypsum Karst Manifestations Of The Castile Formation: Eddy County, New Mexico And Culberson County, Texas, Usa, Kevin W. Stafford, Raymond Nance, Laura Rosales-Lagarde, Penelope J. Boston

International Journal of Speleology

Permian evaporites of the Castile Formation crop out over ~1,800 km2 in the western Delaware Basin (Eddy County, New Mexico and Culberson County, Texas, USA) with abundant and diverse karst manifestations. Epigene karst occurs as well-developed karren on exposed bedrock, while sinkholes dominate the erosional landscape, including both solutional and collapse forms. Sinkhole analyses suggest that more than half of all sinks are the result of upward stoping of subsurface voids, while many solutional sinks are commonly the result of overprinting of collapsed forms. Epigene caves are laterally limited with rapid aperture decreases away from insurgence, with passages developed …


Hydrodynamic Aspect Of Caves, Mitja Prelovšek, Janez Turk, Franci Gabrovšek Jan 2008

Hydrodynamic Aspect Of Caves, Mitja Prelovšek, Janez Turk, Franci Gabrovšek

International Journal of Speleology

From a hydrological point of view, active caves are a series of connected conduits which drain water through an aquifer. Water tends to choose the easiest way through the system but different geological and morphological barriers act as flow restrictions. The number and characteristics of restrictions depends on the particular speleogenetic environment, which is a function of geological, geomorphological, climatological and hydrological settings. Such a variety and heterogeneity of underground systems has presented a challenge for human understanding for many centuries. Access to many underground passages, theoretical knowledge and recent methods (modeling, water pressure-resistant dataloggers, precise sensors etc.) give us …


Contribution Of Artificial Galleries To The Knowledge Of Karstic System Behaviour In Addition To Natural Cavern Data, Benjamin Garry, Thibaut Blondel, Christophe Emblanch, Christophe Sudre, Séverine Bilgot, Alain Cavaillou, Daniel Boyer, Michel Auguste Jan 2008

Contribution Of Artificial Galleries To The Knowledge Of Karstic System Behaviour In Addition To Natural Cavern Data, Benjamin Garry, Thibaut Blondel, Christophe Emblanch, Christophe Sudre, Séverine Bilgot, Alain Cavaillou, Daniel Boyer, Michel Auguste

International Journal of Speleology

The study of karstic systems is mainly based on hydrodynamic and hydrochemical data collected at system inlets (rainfall) and outlets (springs). Indeed, some complementary data base coming from speleological and hydrogeological explorations of natural cavities exist. However, they are not completely representative of all the types of flows. These kinds of flow which have a large part in general hydrodynamics of a system are already the result of a structured organization of karst due to complex phenomena of limestone dissolution. Artificial galleries have the advantage to be easily accessible. Moreover, they cut randomly flows which are much less structured or …


Tracer Tests In Karst Hydrogeology And Speleology, Nico Goldscheider, Joe Meiman, Michiel Pronk, Christopher Smart Jan 2008

Tracer Tests In Karst Hydrogeology And Speleology, Nico Goldscheider, Joe Meiman, Michiel Pronk, Christopher Smart

International Journal of Speleology

This article presents an introduction to the fundamentals of tracing techniques and their application in cave and karst environments, illustrated by case studies from the Mammoth Cave, USA, and a small experimental site in Switzerland. The properties and limitations of the most important artificial tracers are discussed, and the available methods of tracer injection, sampling, online monitoring and laboratory analysis are presented. Fully quantitative tracer experiments result in continuous or discrete concentration-time data series, i.e. breakthrough curves, and concomitant discharge data, which make it possible to obtain detailed information about groundwater flow and contaminant transport. Within the frame of speleological …


Hydrogeochemical Processes As Environmental Indicators In Drip Water: Study Of The Cueva Del Agua (Southern Spain), Angel Fernandez-Cortes, Jose Maria Calaforra, Francisco Sánchez-Martos Jan 2008

Hydrogeochemical Processes As Environmental Indicators In Drip Water: Study Of The Cueva Del Agua (Southern Spain), Angel Fernandez-Cortes, Jose Maria Calaforra, Francisco Sánchez-Martos

International Journal of Speleology

Karst caves exhibit a wide range of hydrological and hydrochemical responses to infiltration events, due to their physical heterogeneity in space and dynamic variability over time, and due to non-Gaussian inputs (rain) and outputs (discharge). This paper reviews different approaches of studying seepage water in caves, in order to understand the infiltration regimen in the non-saturated zone of karst areas. As an illustration, we describe a four-year study of the active carbonate-water system in the Cueva del Agua (Granada, southern Spain) that automatically logs the discharge from a stalactite. The results indicate that: (1) the drip water regime is not …


Subsurface Characterization And Seuqence Stratigraphy Of Late Mississippian Strata In The Black Warrior Basin, Alabama And Mississippi, Carrie A. Kidd Jan 2008

Subsurface Characterization And Seuqence Stratigraphy Of Late Mississippian Strata In The Black Warrior Basin, Alabama And Mississippi, Carrie A. Kidd

University of Kentucky Master's Theses

A depositional framework for the Mississippian (Chesterian) Pride Mountain Formation/Hartselle Sandstone clastic tongue and the lower Bangor Limestone carbonate ramp in the Black Warrior basin, Mississippi and Alabama, is constructed from approximately 250 geophysical well logs, 15 well cuttings descriptions, and outcrop data. The framework is based upon cross sections, isopach maps, and transgressive-regressive sequence stratigraphy.

The Lowndes-Pickens synsedimentary fault block controlled sediment dispersal in during Pride Mountain/Hartselle deposition. The basin filled from the southwest, which pushed the depocenter northeastward during Hartselle deposition. The Hartselle sub-basin is composed of the Hartselle barrier-island and back-barrier deposits to the southwest, including the …


Integrated Geophysical Imaging Of Subsurface Geologic Conditions Across A Contaminant Plume, Mccracken County, Kentucky, Cora A. Blits Jan 2008

Integrated Geophysical Imaging Of Subsurface Geologic Conditions Across A Contaminant Plume, Mccracken County, Kentucky, Cora A. Blits

University of Kentucky Master's Theses

Over 7.8 km of seismic reflection data and 2 km of electrical resistivity data were acquired, processed, and interpreted during this multi-method geophysical study. Objectives included the definition of geologic conditions underlying a contaminant plume in McCracken County, western Kentucky, and the determination of the potential for structural control on the rate and direction of plume migration. Both geophysical methods indicate the presence of multiple high-angle normal faults outlining a series of asymmetric grabens ranging in width from 160 m to almost 300 m and striking between N40°E and N45°E. There was agreement between the two methods on fault location …


Textural Analysis Of A Rhyolite Dike Of The Southern Oklahoma Aulacogen At Medicine Park, Oklahoma, Sean Patrick O'Donnell Jan 2008

Textural Analysis Of A Rhyolite Dike Of The Southern Oklahoma Aulacogen At Medicine Park, Oklahoma, Sean Patrick O'Donnell

Masters Theses

"Detailed analysis of the modal abundance and crystal size distribution (CSD) of glomerocrystic quartz and alkali feldspar phenocrysts in a porphyritic "rhyolite" dike at Medicine Park, Oklahoma were integrated with known phase relationships in the system SiO₂-NaAlSi₃O₈-KAlSi₃-O₈-H₂O to constrain the history of this intrusion"--Abstract, page iv.


The Carbonatite-Hosted Apatite Deposit Of Jacupiranga, Se Brazil: Styles Of Mineralization, Ore Characterization And Association With Mineral Processing, Paula Regina Alves Jan 2008

The Carbonatite-Hosted Apatite Deposit Of Jacupiranga, Se Brazil: Styles Of Mineralization, Ore Characterization And Association With Mineral Processing, Paula Regina Alves

Masters Theses

"The carbonatite-hosted apatite deposit of Jacupiranga is located in southeastern Brazil. The major styles of apatite mineralization are veins or veinlets, small pods or patches, disseminated apatite, and massive aggregates (locally). The concentration of apatite involves grinding of the carbonatite, removal of magnetite with a magnet drum, size classification with cyclones, and flotation to suppress carbonates and collect apatite. Samples of carbonatite were collected from more recent exposures of the mine and drill holes. This study utilized a variety of microscopy methods, namely transmitted and reflected light, cathodoluminescence (CL), and scanning electron microscopy (with wavelength-dispersive spectrometers for mineral compositions)"--Abstract, page …


Shear Wave Splitting And Mantle Flow Associated With The Deflected Pacific Slab Beneath Northeast Asia, Kelly H. Liu, Stephen S. Gao, Yuan Gao, Jing Wu Jan 2008

Shear Wave Splitting And Mantle Flow Associated With The Deflected Pacific Slab Beneath Northeast Asia, Kelly H. Liu, Stephen S. Gao, Yuan Gao, Jing Wu

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

A total of 361 SKS and five local S wave splitting measurements obtained at global and regional seismic network stations in NE China and Mongolia are used to infer the characteristics of mantle fabrics beneath northeast Asia. Fast polarization directions at most of the stations in the western part of the study area are found to be consistent with the strike of local geological features. The dominant fast directions at the eastern part, beneath which seismic tomography and receiver function studies revealed a deflected slab in the mantle transition zone (MTZ), are about 100° from north, which are almost exactly …


Quantifying Twentieth Century Glacier Change In The Sierra Nevada, California, Hassan J. Basagic Jan 2008

Quantifying Twentieth Century Glacier Change In The Sierra Nevada, California, Hassan J. Basagic

Dissertations and Theses

Numerous small alpine glaciers occupy the high elevation regions of the central and southern Siena Nevada, California. These glaciers change size in response to variations in climate and are therefore important indicators of climate change. An inventory based on USGS topographic maps (l :24,000) revealed 1719 glaciers and perennial snow and ice features for a total area of 39.l5 ±7.52 km2. The number of 'true' glaciers, versus non-moving ice, is estimated to be 118, covering 15.87 ± 1.69 Km2. All glaciers were located on north to northeast aspects, at elevations >3000 m. Historical photographs, geologic evidence, …


Turbulent Lifestyle: Microbial Mats On Earth’S Sandy Beaches—Today And 3 Billion Years Ago, Nora Noffke Jan 2008

Turbulent Lifestyle: Microbial Mats On Earth’S Sandy Beaches—Today And 3 Billion Years Ago, Nora Noffke

OES Faculty Publications

Archean Earth history is very difficult to reconstruct. Until recently, only bacterial cells preserved in chert, microborings, and stromatolites provided the few clues to ancient life. Now, siliciclastic “microbially induced sedimentary structures” (MISS) are adding to our knowledge of both past life and paleoenvironments. MISS rise from the interaction of photoautotrophic microbial mats with physical sediment dynamics in siliciclastic, shallow-marine settings. Archean MISS can be understood through observations of living microbial mats and modern biotic-physical sedimentary processes. Such geobiological studies are key to the interpretation of the early evolution of prokaryotes. For example, the 2.9 Ga Pongola Supergroup, South Africa, …


Introduction To Special Section On Microcosms In Ice: The Biogeochemistry Of Cryoconite Holes, Andrew G. Fountain, Martyn Tranter Jan 2008

Introduction To Special Section On Microcosms In Ice: The Biogeochemistry Of Cryoconite Holes, Andrew G. Fountain, Martyn Tranter

Geology Faculty Publications and Presentations

Cryoconite holes are small, water filled, cylindrical melt-holes on glacial ice surface. Cryoconite, 'cold dust,' refers to the thin layer of sediment at the hole bottom. The holes form from surficial sediment patches that absorbs more solar radiation than the surrounding ice and which preferentially melt into the glacier forming a cylindrical water-filled hole. These holes form on the ice-covered, as opposed to snow covered, parts of glaciers world-wide, wherever there is sufficient energy for melting. Biogeochemically, cryoconite holes are interesting because the sediment is inncoculated with biologic material, a fraction of which thrives in the cryoconite environment of near-freezing …


Plagioclase Populations And Zoning In Dacite Of The 2004–2005 Mount St. Helens Eruption: Constraints For Magma Origin And Dynamics, Martin J. Streck, Cindy A. Broderick, Carl R. Thornber, Michael A. Clynne, John S. Pallister Jan 2008

Plagioclase Populations And Zoning In Dacite Of The 2004–2005 Mount St. Helens Eruption: Constraints For Magma Origin And Dynamics, Martin J. Streck, Cindy A. Broderick, Carl R. Thornber, Michael A. Clynne, John S. Pallister

Geology Faculty Publications and Presentations

We investigated plagioclase phenocrysts in dacite of the 2004–5 eruption of Mount St. Helens to gain insights into the magmatic processes of the current eruption, which is char­acterized by prolonged, nearly solid-state extrusion, low gas emission, and shallow seismicity. In addition, we investigated plagioclase of 1980–86 dacite.

Light and Nomarski microscopy were used to texturally characterize plagioclase crystals. Electron microprobe analy­ses measured their compositions. We systematically mapped and categorized all plagioclase phenocrysts in a preselected area according to the following criteria: (1) occurrence of zones of acicular orthopyroxene inclusions, (2) presence of dissolution surface(s), and (3) spatial association of 1 …


The Role Of The Epikarst In Karst And Cave Hydrogeology: A Review, Paul W. Williams Jan 2008

The Role Of The Epikarst In Karst And Cave Hydrogeology: A Review, Paul W. Williams

International Journal of Speleology

The epikarst (also known as the subcutaneous zone) comprises highly weathered carbonate bedrock immediately beneath the surface or beneath the soil (when present) or exposed at the surface. Porosity and permeability are higher near the surface than at depth, consequently after recharge percolating rainwater is detained near the base of the epikarst, the detention ponding producing an epikarstic aquifer. Such an aquifer is found only where the uppermost part of the vadose zone is very weathered compared to the bedrock at depth. Sometimes this contrast in porosity and permeability does not occur either because the epikarst has been scraped off …


Some Applications Of Geochemical And Isotopic Techniques To Hydrogeology Of The Caves After Research In Two Sites (Nerja Cave-S Spain And Fourbanne System-French Jura), Jacques Mudry, Bartolomé Andreo, Arnaud Charmoille, Cristina Liñán, Francisco Carrasco Jan 2008

Some Applications Of Geochemical And Isotopic Techniques To Hydrogeology Of The Caves After Research In Two Sites (Nerja Cave-S Spain And Fourbanne System-French Jura), Jacques Mudry, Bartolomé Andreo, Arnaud Charmoille, Cristina Liñán, Francisco Carrasco

International Journal of Speleology

Caves constitute privileged sampling spots to investigate the hydrochemical behaviour of infiltration, but the representative nature of samples can limit their reach. Taking this into account many results can be obtained from chemistry of water sampled in the caves. Carbonate tracers enable to reconstruct the ‘history’ of drip water water, including rainfall and temperatures. Moreover, permanent drip waters prove durability of water stored in the unsaturated zone over the cave, and lags between rain inputs and drip output enable to evaluate transit time through the unsaturated zone. The comparison of input/output concentrations can also contribute to estimate the local water …


The Origin Of The Bemaraha Tsingy (Madagascar), Márton Veress, Dénes Lóczy, Zoltán Zentai, Gábor Tóth, Roland Schläffer Jan 2008

The Origin Of The Bemaraha Tsingy (Madagascar), Márton Veress, Dénes Lóczy, Zoltán Zentai, Gábor Tóth, Roland Schläffer

International Journal of Speleology

On Madagascar the most representative occurrences of tsingy are at Ankarana and Bemaraha. The tsingy are built up of giant grikes developed along cracks as well as karren features of much smaller size which cover the surfaces between grikes. We investigated the Bemaraha tsingy of Madagascar (surveyed profiles, measured grike directions, etc.) in order to reconstruct their development. The observations indicate that the majority of grikes of the tsingy are created from caves formed under the karst water table and subsequently opened up to the surface. The predominant processes may have been downward progressing dissolution or the collapse of cave …