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Genesis Of Schlottenkarren On The Avon Peninsula Of Nova Scotia (Canada) With Implications For The Geochronology Of Evaporite Karsts And Caves Of Atlantic Canada, Max Moseley 2017 independent researcher

Genesis Of Schlottenkarren On The Avon Peninsula Of Nova Scotia (Canada) With Implications For The Geochronology Of Evaporite Karsts And Caves Of Atlantic Canada, Max Moseley

International Journal of Speleology

Exposed schlottenkarren karst terrains developed on gypsum-anhydrite evaporites in the Canadian Maritime provinces might be post-Glacial landscape features (formed on glacially-denuded rocks after they are uncovered by progressive erosion of overlying glacial tills) or exhumed pre-Last Glacial Maximum (LGM) morphologies (filled with glacial till and revealed by erosion of the tills). In this paper the hydrological conditions necessary for the formation of schlottenkarren, the speleogenetic processes involved and their chronology are reconsidered and reinterpreted. It is proposed that they are essentially pre-LGM features which have survived from the Wisconsinan. It is concluded that the degree of glacial scouring and denudation ...


Integrated Approach For Sinkhole Evaluation And Evolution Prediction In The Central Ebro Basin (Ne Spain), Oscar Pueyo Anchuela, Andrés Pocoví Juan, Antonio M. Casas Sainz, Javier Gracia Abadias, Carlos L. Liesa Carrera 2017 Universidad de Zaragoza

Integrated Approach For Sinkhole Evaluation And Evolution Prediction In The Central Ebro Basin (Ne Spain), Oscar Pueyo Anchuela, Andrés Pocoví Juan, Antonio M. Casas Sainz, Javier Gracia Abadias, Carlos L. Liesa Carrera

International Journal of Speleology

Evaluation of karst hazards benefits from the integration of different techniques, methodologies and approaches. Each one presents a different signature and is sensitive to certain indicators related to karst hazards. In some cases, detailed analysis permits the evaluation of representativeness either from isolated approaches or by means of integrated analyses. In this study, we present the evaluation of an area with high density of karstic collapses at different evolutionary stages through the integration of surficial, historical, geomorphological and geophysical data in order to finally define the evolutionary model for karst activity development. The obtained dataset permits to identify different steps ...


Karst Development Of An Evaporitic System And Its Hydrogeological Implications Inferred From Gis-Based Analysis And Tracing Techniques, José M. Gil-Márquez, Juan A. Barberá, Matías Mudarra, Bartolomé Andreo, Jorge Prieto-Mera, Damián Sánchez, L. David Rizo-Decelis, Manuel Argamasilla, José M. Nieto, Beatríz de la Torre 2017 University of Málaga

Karst Development Of An Evaporitic System And Its Hydrogeological Implications Inferred From Gis-Based Analysis And Tracing Techniques, José M. Gil-Márquez, Juan A. Barberá, Matías Mudarra, Bartolomé Andreo, Jorge Prieto-Mera, Damián Sánchez, L. David Rizo-Decelis, Manuel Argamasilla, José M. Nieto, Beatríz De La Torre

International Journal of Speleology

The geomorphological characteristics and hydrogeological functioning of a geologically heterogeneous evaporitic karst plateau in Southern Spain were studied. Land surface information (LiDAR data) was used to analyze the shape and distribution of closed depressions. An artificial tracer test and monitoring of the natural responses of the main spring have allowed to infer the karstic development of the studied system. Three dyes were injected in selected swallow holes to trace the main groundwater flowpaths and to estimate the dimension of the conduit network. Discharge, electrical conductivity and temperature were monitored in the groundwater that drains the evaporitic plateau during an individual ...


Interpretive Geologic Cross Sections Across Lower Platte North Natural Resources District, Nebraska (Ccs-20), Dana Divine 2017 University of Nebraska - Lincoln

Interpretive Geologic Cross Sections Across Lower Platte North Natural Resources District, Nebraska (Ccs-20), Dana Divine

Conservation and Survey Division

No abstract provided.


Gravitational Study Of The Hastings Salt Dome And Associated Faults In Brazoria And Galveston Counties,Texas, Francis C. Okocha 2017 Stephen F. Austin State University

Gravitational Study Of The Hastings Salt Dome And Associated Faults In Brazoria And Galveston Counties,Texas, Francis C. Okocha

Electronic Theses and Dissertations

Salt domes are important geological structures because they are potential major hydrocarbon traps and have a profound effect on overlying strata in the subsurface. Over five hundred salt domes have been located on the United States Gulf Coast region, including the Hastings Salt Dome. Hastings Oil Field is located about 40.2 km (25 miles) southeast of Houston, Texas. The Hasting oil field was discovered in 1934 and it was considered the largest oil reserve on the Gulf Coast. Its peak production of 75,000 BOPD (barrels of oil per day) was recorded in 1977 and it had a cumulative ...


Integration Of Multi-Criteria And Nearest Neighbour Analysis With Kernel Density Functions For Improving Sinkhole Susceptibility Models: The Case Study Of Enemonzo (Ne Italy), Chiara Calligaris, Stefano Devoto, Jorge P. Galve, Luca Zini, José V. Pérez-Peña 2017 Trieste University

Integration Of Multi-Criteria And Nearest Neighbour Analysis With Kernel Density Functions For Improving Sinkhole Susceptibility Models: The Case Study Of Enemonzo (Ne Italy), Chiara Calligaris, Stefano Devoto, Jorge P. Galve, Luca Zini, José V. Pérez-Peña

International Journal of Speleology

The significance of intra-mountain valleys to infrastructure and human settlements and the need to mitigate the geo-hazard affecting these assets are fundamental to the economy of Italian alpine regions. Therefore, there is a real need to recognize and assess possible geo-hazards affecting them. This study proposes the use of GIS-based analyses to construct a sinkhole susceptibility model based on conditioning factors such as land use, geomorphology, thickness of shallow deposits, distance to drainage network and distance to faults. Thirty-two models, applied to a test site (Enemonzo municipality, NE Italy), were produced using a method based on the Likelihood Ratio (λ ...


Assessing Landslide Susceptibility With Gis Using Qualitative & Quantitative Methods In Knox County, Nebraska, Christian J. Cruz 2017 University of Nebraska-Lincoln

Assessing Landslide Susceptibility With Gis Using Qualitative & Quantitative Methods In Knox County, Nebraska, Christian J. Cruz

Theses and Dissertations in Geography

This thesis assesses landslide susceptibility using data from LiDAR DEMs, land cover, and soil surveys. Data were assessed quantitatively through Bayesian logistic regression within a geographic information system (GIS) and statistical software to produce a landslide susceptibility map. The study area exhibits moderate relief where bluffs along the Missouri River valley gradually recede into rolling loess-mantled hills further to the south and southeast in Knox County. The six factors used to determine susceptibility to landslides are: land cover, parent material, slope aspect, slope curvature slope degree, and soil series. My findings show an increase in slope is the most significant ...


The Groundwater Atlas Of Richardson County, Nebraska, Dana P. Divine, Leslie M. Howard 2017 University of Nebraska - Lincoln

The Groundwater Atlas Of Richardson County, Nebraska, Dana P. Divine, Leslie M. Howard

Conservation and Survey Division

The purpose of this groundwater atlas is to synthesize a wealth of hydrogeologic data for Richardson County that has not been published in readily accessible formats previously. Many of the maps presented herein are based on data from registered well logs and test hole logs that are publicly available on-line, which become more valuable when compiled, analyzed, and discussed as a whole. The focus of the maps presented in this report is the accessibility of groundwater for pumping.


Rock Art Management And Landscape Change: Mixed Field Assessment Techniques For Cultural Stone Decay, Kaelin M. Groom 2017 University of Arkansas, Fayetteville

Rock Art Management And Landscape Change: Mixed Field Assessment Techniques For Cultural Stone Decay, Kaelin M. Groom

Theses and Dissertations

As tourism continues to grow as one of the world’s most ubiquitous markets, the development and promotion of non-invasive techniques for cultural stone decay analysis and landscape change are vital to establishing conditional base-lines to best aid cultural heritage management (CRM) efficacy. Using rock art as a medium, this dissertation presents three independent case studies employing the Rock Art Stability Index (RASI) and repeat photography to explore the merits of mixed rapid field assessment techniques in relation to CRM and heritage tourism. While rock art is only one example of irreplaceable world heritage resources, examining how they decay and ...


Comparison Of Flow Dynamics And Bifurcation Angles In Tributary And Distributary Channel Networks, Thomas Coffey 2017 University of Arkansas, Fayetteville

Comparison Of Flow Dynamics And Bifurcation Angles In Tributary And Distributary Channel Networks, Thomas Coffey

Theses and Dissertations

The dynamics of channel mouth bifurcations on river deltas can be understood using theory developed in tributary channel networks. Bifurcations in groundwater-fed tributary networks have been shown to evolve dependent on diffusive ground water flow patterns

directly adjacent to the channel network, producing a critical angle of 72°. We test the hypothesis that bifurcation angles in distributary channel networks are likewise dictated by a diffusive external flow field, in this case the shallow surface water surrounding the subaqueous portion of distributary channels in a deltaic setting. We measured 25 unique distributary bifurcations in an experimental delta and 197 bifurcations in ...


Soft-Bed Experiments Beneath Engabreen, Norway: Regelation Infiltration, Basal Slip And Bed Deformation, Neal R. Iverson, Thomas S. Hooyer, Urs H. Fischer, Denis Cohen, Peter L. Moore, M. Jackson, G. Lappegard, J. Kohler 2017 Iowa State University

Soft-Bed Experiments Beneath Engabreen, Norway: Regelation Infiltration, Basal Slip And Bed Deformation, Neal R. Iverson, Thomas S. Hooyer, Urs H. Fischer, Denis Cohen, Peter L. Moore, M. Jackson, G. Lappegard, J. Kohler

Neal Iverson

To avoid some of the limitations of studying soft-bed processes through boreholes, a prism of simulated till (1.8 m × 1.6 m × 0.45 m) with extensive instrumentation was constructed in a trough blasted in the rock bed of Engabreen, a temperate glacier in Norway. Tunnels there provide access to the bed beneath 213 m of ice. Pore-water pressure was regulated in the prism by pumping water to it. During experiments lasting 7–12 days, the glacier regelated downward into the prism to depths of 50– 80 mm, accreting ice-infiltrated till at rates predicted by theory. During periods of ...


Subglacial Clast/Bed Contact Forces, John Byers, Denis Cohen, Neal R. Iverson 2017 Iowa State University

Subglacial Clast/Bed Contact Forces, John Byers, Denis Cohen, Neal R. Iverson

Neal Iverson

A laboratory device was built to measure the forces that ice exerts on a 0.05 m diameter rigid plastic sphere in two different configurations: in contact with a flat bed or isolated from the bed. Measurements indicated that bed-normal contact forces were 1.8 times larger than drag forces due to creeping flow past a slippery sphere isolated from the bed. Measurements of forces as a function of the bed-normal ice velocity, estimations of the ice viscosity parameter and observations of markers in the ice indicate ice is Newtonian with a viscosity of ∼1.3 × 1011 Pa s. Newtonian ...


Reply To "Comment On ‘Preexisting Fractures And The Formation Of An Iconic American Landscape: Tuolumne Meadows, Yosemite National Park, Usa,’ By Jeffrey P. Schaffer”, Richard A. Becker, Basil Tikoff, Paul R. Riley, Neal R. Iverson 2017 University of Wisconsin-Madison

Reply To "Comment On ‘Preexisting Fractures And The Formation Of An Iconic American Landscape: Tuolumne Meadows, Yosemite National Park, Usa,’ By Jeffrey P. Schaffer”, Richard A. Becker, Basil Tikoff, Paul R. Riley, Neal R. Iverson

Neal Iverson

No abstract provided.


Magnetic Fabric Of Sheared Till: A Strain Indicator For Evaluating The Bed Deformation Model Of Glacier Flow, Thomas S. Hooyer, Neal R. Iverson, France Lagroix, Jason F. Thomason 2017 University of Wisconsin-Madison

Magnetic Fabric Of Sheared Till: A Strain Indicator For Evaluating The Bed Deformation Model Of Glacier Flow, Thomas S. Hooyer, Neal R. Iverson, France Lagroix, Jason F. Thomason

Neal Iverson

[1] Wet-based portions of ice sheets may move primarily by shearing their till beds, resulting in high sediment fluxes and the development of subglacial landforms. This model of glacier movement, which requires high bed shear strains, can be tested using till microstructural characteristics that evolve during till deformation. Here we examine the development of magnetic fabric using a ring shear device to deform two Wisconsin-age basal tills to shear strains as high as 70. Hysteresis experiments and the dependence of magnetic susceptibility of these tills on temperature demonstrate that anisotropy of magnetic susceptibility (AMS) develops during shear due to the ...


Glacial Landscape Evolution By Subglacial Quarrying: A Multiscale Computational Approach, Sofie V. Ugelvig, David L. Egholm, Neal R. Iverson 2017 Aarhus University

Glacial Landscape Evolution By Subglacial Quarrying: A Multiscale Computational Approach, Sofie V. Ugelvig, David L. Egholm, Neal R. Iverson

Neal Iverson

Quarrying of bedrock is a primary agent of subglacial erosion. Although the mechanical theory behind the process has been studied for decades, it has proven difficult to formulate the governing principles so that large-scale landscape evolution models can be used to integrate erosion over time. The existing mechanical theory thus stands largely untested in its ability to explain postglacial topography. In this study we relate the physics of quarrying to long-term landscape evolution with a multiscale approach that connects meter-scale cavities to kilometer-scale glacial landscapes. By averaging the quarrying rate across many small-scale bedrock steps, we quantify how regional trends ...


Glacier-Bed Geomorphic Processes And Hydrologic Conditions Relevant To Nuclear Waste Disposal, Neal R. Iverson, Mark Person 2017 Iowa State University

Glacier-Bed Geomorphic Processes And Hydrologic Conditions Relevant To Nuclear Waste Disposal, Neal R. Iverson, Mark Person

Neal Iverson

Characterizing glaciotectonic deformation, glacial erosion and sedimentation, and basal hydrologic conditions of ice sheets is vital for selecting sites for nuclear waste repositories at high latitudes. Glaciotectonic deformation is enhanced by excess pore pressures that commonly persist near ice sheet margins. Depths of such deformation can extend locally to a few tens of meters, with depths up to approximately 300 m in exceptional cases. Rates of glacial erosion are highly variable (0.05–15 mm a−1), but ratesa−1 are expected in tectonically quiescent regions. Total erosion probably not exceeding several tens of meters is expected during a glacial ...


Ring-Shear Studies Of Till Deformation: Coulomb-Plastic Behavior And Distributed Strain In Glacier Beds, Neal R. Iverson, Thomas S. Hooyer, Robert W. Baker 2017 Iowa State University

Ring-Shear Studies Of Till Deformation: Coulomb-Plastic Behavior And Distributed Strain In Glacier Beds, Neal R. Iverson, Thomas S. Hooyer, Robert W. Baker

Neal Iverson

A ring-shear device was used to study the factors that control the ultimate(steady) strength of till at high shear strains.Tests at a steady strain rate and at different stresses normal to the shearing direction yielded ultimate friction angles of 26.3° and 18.6° for tills containing 4% and 30% clay-sized particles, respectively Other tests at steady normal stresses and variable shear-strain rates indicated a tendency for both tills to weaken slightly with increasing strain rate. This weakening may be due to small increases in till porosity.These results provide no evidence of viscous behavior and suggest that ...


Rate-Weakening Drag During Glacier Sliding, Lucas K. Zoet, Neal R. Iverson 2017 University of Wisconsin-Madison

Rate-Weakening Drag During Glacier Sliding, Lucas K. Zoet, Neal R. Iverson

Neal Iverson

Accurately specifying the relationship between basal drag on a hard, rough glacier bed and sliding speed is a long-standing and central challenge in glaciology. Drag on a rigid bed consisting of steps with linear treads inclined upglacier—a good idealization for the bedrock morphology of some hard-bedded glaciers—has been considered in sliding theories but never studied empirically. Balancing forces parallel to step treads indicates that drag should be independent of sliding speed and cavity size and set by the limit-equilibrium condition sometimes called Iken's bound. In this study we used a large ring-shear device to slide ice at ...


Role Of Transient Water Pressure In Quarrying: A Subglacial Experiment Using Acoustic Emissions, Denis Cohen, Thomas S. Hooyer, Neal R. Iverson, Jason Thomason, M. Jackson 2017 Iowa State University

Role Of Transient Water Pressure In Quarrying: A Subglacial Experiment Using Acoustic Emissions, Denis Cohen, Thomas S. Hooyer, Neal R. Iverson, Jason Thomason, M. Jackson

Neal Iverson

Probably the most important mechanism of glacial erosion is quarrying: the growth and coalescence of cracks in subglacial bedrock and dislodgement of resultant rock fragments. Although evidence indicates that erosion rates depend on sliding speed, rates of crack growth in bedrock may be enhanced by changing stresses on the bed caused by fluctuating basal water pressure in zones of ice-bed separation. To study quarrying in real time, a granite step, 12 cm high with a crack in its stoss surface, was installed at the bed of Engabreen, Norway. Acoustic emission sensors monitored crack growth events in the step as ice ...


Preexisting Fractures And The Formation Of An Iconic American Landscape: Tuolumne Meadows, Yosemite National Park, Usa, Richard A. Becker, Basil Tikoff, Paul R. Riley, Neal R. Iverson 2017 University of Wisconsin-Twin Cities

Preexisting Fractures And The Formation Of An Iconic American Landscape: Tuolumne Meadows, Yosemite National Park, Usa, Richard A. Becker, Basil Tikoff, Paul R. Riley, Neal R. Iverson

Neal Iverson

Tuolumne Meadows, in Yosemite National Park (USA), is a large sub-alpine meadow in the Sierra Nevada Mountains. Immediately adjacent to Tuolumne Meadows—and underlain by the same bedrock lithology (Cathedral Peak Granodiorite)—are vertical rock faces that provide exceptional opportunities to climbers. While the presence of a broad meadow suggests bedrock erodibility, the vertical rock walls indicate bedrock durability. We propose that the Tuolumne Meadows’s landscape is the result of variable glacial erosion due to the presence or absence of pre-existing bedrock fractures. The meadows and valleys formed because of concentrated tabular fracture clusters—a distinctive and locally pervasive ...


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