Earth Sciences - Theses, Dissertations, and other Required Graduate Degree Essays

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Sedimentology, ichnology, and stratigraphy of the Sparky, Waseca, and McLaren Alloformations, West-Central Saskatchewan, Canada

Date created: 
2012-03-21
Abstract: 

The Lower Cretaceous Sparky, Waseca, and McLaren alloformations (Upper Mannville Group) of west-central Saskatchewan comprise an interval up to 60 m thick, consisting of weakly consolidated sandstones, shales, heterolithic bedsets and minor coals deposited in shallow-marine to coastal plain/delta plain environments. Thirteen facies are recognized. These facies are grouped into six spatially recurring facies associations. Facies Association 1 (FA1) corresponds to sediments deposited below fairweather wave base but above storm wave base. Facies associations 2 and 3 (FA2 and FA3) coarsen upward and represent the progradation of wave- and storm-dominated shorefaces as well as mixed river- and wave-influenced deltas, respectively. Facies Association 4 (FA4) commonly displays fining-upward successions, interpreted as distributary channel or fluvio-estuarine deposits, depending upon their stratigraphic context. Facies Association 5 (FA5) is broadly similar to FA2, but is ichnologically distinct. The succession is characterized by low-diversity, impoverished trace-fossil suites with variable bioturbation intensities that are interpreted to record deposition in shallow brackish-water bays. Facies Association 6 (FA6) successions are interpreted as coastal plain/delta plain deposits. Upper Mannville strata can be separated into parts of two depositional sequences. The main deposits of the lower sequence comprise two highstand systems tracts (HST), corresponding to the Sparky Alloformation and the Lower Waseca Allomember. The base of the Lower Waseca marks the onset of a transgressive systems tract (TST). A maximum flooding surface (MFS) marks the end of transgression and the resumption of progradation for the remainder of the Lower Waseca. Following highstand progradation a relative base-level fall produced a subaerial unconformity, which marks the base of the upper sequence. Fluvial valley incision led to sediment bypass, and deposition of forced regressive and lowstand shoreface and delta complexes of the falling stage systems tract (FSST) and lowstand systems tract (LST) towards the northern part of the study area. TST accumulation is largely confined to estuarine infill of the incised valleys of the Upper Waseca Allomember. The Upper Waseca is separated from the McLaren Alloformation by a maximum flooding surface (MFS). The overlying McLaren Alloformation marks a return to regional shoreline progradation, and corresponds to a highstand systems tract (HST).

Document type: 
Thesis
Supervisor(s): 
James A. MacEachern
Shahin Dashtgard
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.

Investigation of the Mountain River beryl (emerald variety) occurrence, Mackenzie Mountains, Northwest Territories

Author: 
Date created: 
2012-12-17
Abstract: 

Emerald at the Mountain River emerald occurrence is milky green and occurs in extensional quartz-carbonate veins hosted within organic-poor siliciclastic rocks. Oxygen isotope mineral pair equilibration thermometry indicates mineralization temperatures of 379 to 415°C. Fluid inclusion analyses indicate CO2-N2-bearing brines and homogenization temperatures between 118 and 258°C. Fluid pressures were on the order of 2.4 to 4.0 kbar, corresponding to depths of 9 to 15 km. Pyrite intergrown with emerald yields a 5 point Re-Os model 1 isochron age of 345 ± 20 Ma and an elevated initial 187Os/188Os of 3.2, indicating a crustal source. The fluids involved in emerald mineralization were derived from deep-seated hydrothermal brines, and were likely the same fluids involved in producing the Manetoe facies dolomite and extensive carbonate-hosted zinc-lead occurrences throughout the Mackenzie Platform. The Mountain River emerald occurrence shares many characteristics with Colombian-type emerald deposits. The Colombian emeralds are hosted in organic-rich black shales and formed during compressional deformation via thermochemical sulphate reduction of brines by organic matter. However, the Mountain River occurrence is hosted in organic-poor siliciclastic rocks and formed in an extensional back-arc environment via inorganic sulphate reduction. The Mountain River emerald occurrence thus represents a modification of the Colombian-type deposit model.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Daniel Marshall
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Characterization and interpretation of polythermal structure in two subarctic glaciers

Author: 
Date created: 
2012-11-29
Abstract: 

I use ice-penetrating radar to probe the thermal structure in two small glaciers in the Saint Elias Range, southwestern Yukon. I develop processing workflows to separate bed and englacial reflections in radar and use these to build maps of both bed topography and englacial scattering. Comparison with borehole data shows that englacial scattering occurs in ice at the freezing point. The pattern in thermal structure suggests that the observed regime is dominated by accumulation zone processes. I develop a numerical model to simulate steady and time-dependent thermal regimes in glaciers. Diagnostic simulations support the hypothesis that meltwater entrapment is a critical control on the observed structure. Sensitivity tests suggest a climate sensitivity such that thinning and retreat of the near-surface aquifer may dramatically alter the thermal structure. Prognostic simulations illustrate scenarios in which these polythermal glaciers may cool as climate warms in the future.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Gwenn Flowers
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Modelling topographically-driven groundwater flow in mountains

Author: 
Date created: 
2012-11-19
Abstract: 

The role of groundwater as a component of mountain water systems is poorly understood due to a lack of data for these often remote and inaccessible high relief regions. Yet, two of the main processes that act to replenish water resources for populated valleys, baseflow (BF) and mountain block recharge (MBR), are a direct result of mountain groundwater flow. The research conducted for this thesis involved numerical modelling of 2-D and 3-D domains representing simple generic systems, as well as real topographic scenarios, to investigate the influence of topography on deep groundwater (DG) flow patterns, and the sensitivity of these patterns to uncertainty in recharge (R) and bedrock hydraulic conductivity (K). Regional-scale topographically-driven DG flow patterns that develop in mountain bedrock are reflective of prominent topographic features comprising the mountain block which, for linear-ridge mountain ranges, consist of watershed-bounding ridges, deeply incised primary stream valleys, and triangular facet areas at the mountain front. DG contributing areas for BF at primary stream valleys are generally close to watershed boundaries, and contributing areas for MBR are generally coincident with triangular facet areas. At the regional (~ 10 – 100 km) and sub-catchment (~ 500 m to 2 km) scales, the fundamental characteristics of topographically-driven DG flow patterns are dominant despite smaller-scale variations in topography, and uncertainty in recharge and sub-catchment K heterogeneity. At the local scale, topographically-driven DG flow patterns vary due to uniqueness and complexity of topography, recharge, spatial and/or temporal variability, and K heterogeneities, indicating the importance of understanding these factors for a detailed understanding of DG flow systems. DG flow patterns and boundaries are influenced by the topography of a given catchment as well as surrounding topography and regional topographic setting, and therefore, analysis of DG flow systems and boundaries must consider areas outside the catchment of interest. The results of this study support the development of topography-based predictive tools for conceptualizing DG flow patterns and BF/MBR contributing areas. Numerical modelling using topographic data, which are often the only available data for mountainous areas, provides a convenient approach for preliminary characterization of topographically-driven DG flow patterns in mountains on a site-specific basis.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Diana Allen
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.

The impact of landslides on sediment yield, South Westland, New Zealand

Date created: 
2012-04-12
Abstract: 

Sediment yields in the Southern Alps of New Zealand are among the highest in the world due to high annual precipitation, rapid uplift, weak bedrock and episodic earthquakes. Two neighbouring watersheds, those of the Poerua and Waitangitaona rivers, were studied to determine the impact landslides have on sediment yield. Both watersheds have been recently disturbed by landslides, 1) a large rock avalanche from Mt. Adams in the Poerua River watershed and 2) a failing slope known as the “Gaunt Creek slip” in the Waitangitaona watershed. I conducted a ground penetrating radar survey of the lower Waitangitaona River valley and a dGPS topographic survey of the lower Poerua River valley to determine average sediment yields on different timescales. The estimated sediment yields, which are among the highest in the world, are controlled by differences in the time, size, and character of the landslides that have perturbed the fluvial system.

Document type: 
Thesis
File(s): 
Supervisor(s): 
John Clague
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Assessing risk to groundwater quality using an integrated risk framework

Date created: 
2012-07-23
Abstract: 

Risk to groundwater quality is defined as a function of susceptibility, hazard and consequence. Aquifer susceptibility combines the intrinsic susceptibility of the physical system with potential preferential pathways. Hazard threats are assessed based on the potential impact and probability of release. The consequence is the financial cost of the loss of the resource. The risk assessment methodology is applied to the Township of Langley, BC. The results define vulnerable areas as those where susceptible aquifers coincide with chemical and biological threats. The risk is greatest where vulnerable areas coincide with high potential financial loss: within municipal well capture zones and where wells serve high value agriculture. A regional numerical model was constructed and used to outline capture zones for wells that may be at risk. The model was also used to model contaminant transport and highlight the need to consider horizontal groundwater flow when assessing vulnerability.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Diana Allen
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

The effects of timber harvesting and windthrow on landslide initiation, Southwestern Vancouver Island

Author: 
Date created: 
2011-11-09
Abstract: 

A severe storm in November 2006 caused over 200 landslides on southwestern Vancouver Island. This thesis investigates 48 field truthed landslides and 233 GIS mapped landslides in unlogged and logged terrain. The impact of windthrow, clearcutting, soil properties and root reinforcement on landslide initiation were analysed within eight months after the storm event. The windthrow landslide density was 25 and 123 times the clearcut and natural landslide densities, respectively. Windthrow related landslides were concentrated on south to east aspects, near clearcut boundaries and recent clearcuts (<10 years old). Windthrow landslides occur on steeper, convex, well drained, colluvial slopes with thinner soils than clearcut landslides.This study used a root density and quality approach to define the loss of root reinforcement after logging. The results show a rapid decline over the first 11 years followed by an increase up to 50 years. Root quality shows a similar trend after logging.

Document type: 
Thesis
Supervisor(s): 
Brent Ward
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

The Wernecke igneous clasts in Yukon, Canada: evidence for a Paleoproterozoic volcanic arc terrane at 1.7 Ga and its obduction onto ancestral North America

Date created: 
2011-12-15
Abstract: 

All observed Wernecke igneous clasts (WIC) occur within the 1.60 Ga Wernecke Breccias of Yukon, Canada. The clasts range up to 5.4 million m3 in volume, and comprise the 1.71 Ga Bonnet Plume River Intrusions (BPRI), the Slab volcanics, the Devil volcanics, and the Blackstone River megaclast. The WIC were not emplaced through the <1.64 Ga Wernecke Supergroup (WSG). The BPRI and Devil volcanics have a geochemical affinity with volcanic arcs. The Slab volcanics are more alkaline, like mantle plume or slab-window derived volcanoes. Sm-Nd isotopes indicate that magmas of the BPRI and Devil volcanics assimilated older basement rock. The WIC originated in a terrane that was obducted onto the WSG. Hydrothermal fluids brecciated these units, forming the Wernecke Breccias. WICs derived from the terrane foundered into these breccias to the level of the WSG and were metasomatized. The obducted terrane eroded entirely prior to deposition of the Pinguicula Group.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Derek Thorkelson
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Evolution of glacier-dammed lakes through space and time; Brady Glacier, Alaska, USA

Date created: 
2011-10-21
Abstract: 

Glacier-dammed lakes and their associated jökulhlaups cause severe flooding in downstream areas and substantially influence glacier dynamics. The goal of this dissertation is to identify and characterize the evolution of glacier-dammed lakes to predict their future behaviour using ground-truthed remote sensing techniques and dendrochronology. Brady Glacier in southeast Alaska is particularly well suited for a study of these phenomena because it presently dams ten large (>1 square km) lakes and many smaller ones. This dissertation comprises three studies. First, I used interferometric synthetic aperture radar (InSAR) to identify and characterize three previously unknown subglacial lakes. InSAR allowed me to quantify the vertical displacement and volume of water discharged from the three lakes through time. From the fall of 1995 to the spring of 1996, subsidence ranged from 4 to 26 cm/day and the volume of water discharged ranged from 22,000 ± 2000 to 243,000 ± 14,000 cubic m/day. Subsidence and discharge rates declined significantly during the winter and continued at a lesser rate through March. Second, I used dendrochronology and precise elevation-constrained mapping to date glacially overridden and drowned trees. Brady Glacier impounded Spur Lake to an elevation of 83 m a.s.l. around AD 1830 and 121 m a.s.l. around 1839. The glacier continued to advance, thickening by at least 77 m between ca. 1844 and 1859 at a site down-glacier of Spur Lake on the opposite glacier margin. Farther down-glacier, North Trick Lake began to form by 1861 and reached its highest elevation at approximately 130 m a.s.l. when Brady Glacier reached its maximum extent around 1880. Third, I georeferenced a variety of maps, airphotos, and optical imagery to characterize the evolution of the glacier and lakes and created five bathymetric maps. The main terminus of Brady Glacier has changed little since 1880. However, it downwasted at rates of 2-3 m/yr between 1948 and 2000. The most dramatic retreat (2 km) and downwasting (123 m) occurred adjacent to glacier-dammed lakes. These lakes will continue to evolve and play a pivotal role in the evolution of Brady Glacier. If downwasting and retreat continue at rates comparable to the past, the glacier may return to a tidewater regimen and retreat catastrophically until it stabilizes in shallow water.

Document type: 
Thesis
File(s): 
Supervisor(s): 
John Clague
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.

Two-dimensional waveform tomography of the Queen Charlotte Basin of Western Canada and the Seattle fault zone

Date created: 
2011-12-12
Abstract: 

Two-dimensional frequency domain visco-acoustic waveform tomography is applied to limited-offset marine seismic reflection data from the Queen Charlotte sedimentary Basin of western Canada, and from the Seattle Fault Zone in Puget Sound, Washington. It was possible to obtain high resolution P-wave velocity and attenuation images of the subsurface, and to practically evaluate the effectiveness of the visco-acoustic waveform tomography method. A specific data preconditioning and inversion strategy is developed to recover models to a depth of 1.2 to 1.3 km. The preconditioning of the data converts the field data to a form similar to that predicted by the acoustic waveform modelling algorithm. A multiscale inversion strategy was designed to mitigate non-linearity issues and to improve the estimation of attenuation. The starting velocity model is derived from first arrival traveltime tomography and the starting attenuation model is a homogeneous Q p -value. Four seismic lines in the Queen Charlotte Basin are imaged, and the recovered velocity models aid in interpreting shallow structures such as Quaternary strata and Pliocene faulting. The joint interpretation of the velocity and attenuation models enables the identification of siltstone, shales, the presence of hydrocarbons and seafloor pockmarks. The shallowmost basement rocks are interpreted to be volcanic. Using a section of the seismic data across the Seattle Fault Zone, synthetic visco-acoustic and visco-elastic modelling was used to verify the effectiveness of applying visco-acoustic waveform tomography to visco-elastic data. The results show that visco-acoustic waveform tomography of marine seismic reflection data is reliable when high velocity gradients are absent from the model. Finally, an interpretation is provided for the inversion results across the Seattle Fault Zone. The inverted velocity and attenuation models enable the identification of glacial and post-glacial Pleistocene, Tertiary sedimentary rocks, and Eocene volcanic rocks. Several north-dipping shallow thrust faults, anticlines and a syncline are identified across the Seattle uplift and the Seattle Fault Zone. The orientation of the faults are consistent with the interpretations of the Seattle Fault Zone as either a fault propagating fold with a forelimb breakthrough, or as the leading edge of a triangle zone within a passive roof duplex.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Andrew Calvert
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.