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

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The evolution of the late Paleoproterozoic Wernecke Supergroup, Wernecke Mountains, Yukon, from sedimentation to deformation

Date created: 
2015-04-02
Abstract: 

The Wernecke Supergroup of Yukon is a metasedimentary succession deposited between ca. 1.66 and 1.60 Ga on the northwestern margin of ancestral North America (Laurentia). U-Pb detrital zircon geochronology, major and trace element geochemistry, and Nd isotope geochemistry reveal that the clastic sediments were derived mostly from collisional orogens that resulted from the amalgamation of Laurentia during Paleoproterozoic. Some detritus may have originated from non-North-American terranes such as eastern Australia or exotic arc terranes. Deposition of the Wernecke Supergroup occurred in a passive margin which resulted from the initial breakup of the supercontinent Columbia, and involved separation of northwestern Laurentia from adjacent continents, probably eastern Australia and the Yangtze craton of South China. This reconstruction is similar to the SWEAT configuration proposed for the Neoproterozoic supercontinent Rodinia. The Wernecke Supergroup was deformed at ca. 1.60 Ga by the Racklan orogeny which was accompanied by greenschist facies metamorphism, exhumation and erosion of the Wernecke Supergroup, and obduction of an exotic terrane, named Bonnetia, which was previously located offshore from the northwestern margin of Laurentia. The final stage of the Racklan orogeny was the result of the collision between eastern Australia and western Laurentia in another SWEAT-like configuration. The Racklan orogeny is regarded as part of a long orogenic belt which flanked the supercontinent Columbia at 1.65-1.60 Ga. This belt was developed on Amazonia, Baltica, eastern and southern Laurentia, East Antarctica, East Australia, and northwestern Laurentia. Following Racklan orogeny, a set of hydrothermal fluids intruded and brecciated the Wernecke Supergroup and caused collapse of fragments of the tectonically overlying Bonnetia. This hydrothermal event was responsible for the emplacement of iron oxide-copper-gold (IOCG) mineralization in the area, and is similar in age, and is possibly related to, IOCG deposits located in east Australia and South China.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Derek Thorkelson
Department: 
Science:
Thesis type: 
(Thesis) Ph.D.

Pleistocene stratigraphy, glacial limits and paleoenvironments of White River and Silver Creek, southwest Yukon

Author: 
Date created: 
2014-09-26
Abstract: 

Quaternary glacial and non-glacial sediment exposed at White River and Silver Creek provide a record of environmental change in southwest Yukon for much of the late-Middle to Late Pleistocene. Eighteen sites at White River, located beyond the marine oxygen isotope stage (MIS) 2 glacial limit, contain thick accumulations of till, loess, peat, gravel and glaciolacustrine silt and clay, with tephras, paleosols, plant and insect macrofossils and large mammal fossils. Radiocarbon ages and eleven tephra beds constrain two tills to MIS 4 and 6. These tills correlate to the Gladstone and Reid glaciations and represent the penultimate and maximum all-time limits of the St. Elias lobe of the northern Cordilleran Ice Sheet. Two peat beds located between these tills indicate that interglacial conditions existed in the area during MIS 5e and 5a. Pond sediment deposited during mid-MIS 5 suggests that the sites were covered by an open birch tundra at this time. The MIS 3/2 transition was marked by a treeless, dry steppe-tundra populated by mammoth, horse and bison.The eleven Silver Creek sites, located ~200 km up-ice, contain a similar record of glacial and non-glacial sediment. Infrared-stimulated luminescence (IRSL) and radiocarbon dating constrain the glacial deposits at these sites to MIS 2, 4, either MIS 7 or 6, and to two Early to Middle Pleistocene, Pre-Reid glaciations. Tilting of glaciolacustrine beds of up to 1.9 mm/yr may be from uplift along the Denali fault since MIS 7. Pollen and macrofossils analyses from overlying MIS 3-aged sediment suggest that the environment was dominated by herbs and forbs, with few shrubs and almost no tree pollen at this time. Combined, the White River and Silver Creek sites contain a record of glacial and non-glacial conditions in southwest Yukon since the Middle Pleistocene.The glacial limits in southwest Yukon are markedly different from those in central Yukon. In southwest Yukon, the glacial limits are closely-spaced and were more extensive in the Middle to Late Pleistocene than in the Late Pliocene and Early Pleistocene. In central Yukon, glacial limits are separated by up to 300 km and were most extensive in the latest Pliocene and Early Pleistocene. This suggests that different forcing mechanisms controlled the extents of the St. Elias and Selwyn lobes during successive glaciations. Boundary conditions such as varying substrates, topography, moisture pathways and atmospheric circulation likely had a greater affect than tectonics and sea level on these glacial limits throughout the Plio-Pleistocene.

Document type: 
Thesis
Senior supervisor: 
Brent Ward
Department: 
Science:
Thesis type: 
(Thesis) Ph.D.

Earthquake Loss Estimates, Greater Victoria, British Columbia

Date created: 
2014-08-05
Abstract: 

I compare loss estimates for a range of earthquake scenarios and built environment models for municipalities in Greater Victoria, British Columbia, Canada, using Hazards United States Multi-Hazard version 2.1 (HAZUS) software. Best-estimate losses use region-specific site-condition maps and built-environment inventories updated with municipal assessment information for five scenarios representing subduction-interface, shallow-crustal, and in-slab earthquake types. Losses are higher for a major, near-source, shallow-crustal event than for larger magnitude, great subduction-interface earthquakes. Loss estimates differ by two to three orders of magnitude depending on the source scenario. Site-condition mapping and built-environment updates also significantly affect loss estimates (differences of up to 600% and 450%, respectively), depending on the scenario and loss metric under consideration.

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

Contemporary subsidence and settlement of the Fraser River delta inferred from SqueeSAR(TM)-type InSAR data

Author: 
Date created: 
2014-12-02
Abstract: 

The Fraser River delta in southwestern British Columbia formed over the past 10 000 years and currently supports a population of about 250 000 people. This research focuses on the urbanized and rapidly expanding Richmond area of the Fraser River delta. Dyking, which began in the early 1900s, has prevented flooding and sediment deposition, with the result that the delta plain is subsiding at an average rate of 1-2 mm/a due to the slow, natural consolidation of thick Holocene sediment. Localized higher rates of subsidence stem from anthropogenic sources, notably the application of loads in construction. InSAR data was used to relate load-induced settlement to geology and the spatial and temporal pattern of urbanization. All displacement rates 10 mm/a or more are associated with industrial or large commercial structures. Similar amounts of total settlement are observed from similar sized loads, yet rates of settlement differ, indicating that while load is important in determining total settlement, lithology is as important as load in determining rates of settlement. Holocene sediments underlying the delta are water-saturated, porous, fine sand, silty sand, silt. They are compressible to considerable depth and can experience significant settlement when subjected to structural loads, dewatering, or seismic shaking. No relationship between subsidence rate and surface geology was observed, although surface settlements are generally removed prior to construction. There is an insufficient amount of subsurface data to disentangle lithology and sediment thickness effects. A weak relationship between Holocene thickness and displacement rate has been observed for commercial sized buildings in eastern Richmond with an increase of 0.95 mm/a in the displacement rate for every 100 m of sediment thickness. A weak logarithmic relationship was also observed for the entire RADARSAT dataset.

Document type: 
Thesis
Senior supervisor: 
John Clague
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

Applications of Uncertainty Theory to Rock Mechanics and Geotechnical Mine Design

Author: 
Date created: 
2015-01-07
Abstract: 

Uncertainty analysis remains at the forefront of geotechnical design, due to the predictive nature of the applied discipline. Designs must be analysed within a reliability-based framework, such that inherent risks are demonstrated to decision makers. This research explores this paradigm in three important areas of geotechnical design; namely, continuum, Discrete Fracture Network (DFN) and discontinuum modelling. Continuum modelling examined the negative effects of ignoring spatial heterogeneity on model prediction. This was conducted through the stochastic modelling of spatial heterogeneities found within a large open pit mine slope. DFN analysis introduced a novel approach to fracture generation to solve issues associated with the incorporation of traditional DFNs into geomechanical simulation models. Finally, discontinuum modelling explored the inherent mesh dependencies that exist in UDEC grain boundary models (UDEC-GBM). Conclusions suggest that a transition is required from deterministic to uncertainty based design practices within the geotechnical discipline.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Doug Stead
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

Characterizing Groundwater - Surface Water Interactions within a Mountain to Ocean Watershed, Lake Cowichan, British Columbia

Author: 
Date created: 
2014-11-19
Abstract: 

Watersheds located within a mountain to coast physiographic setting have been described as having a highly inter-connected surface water and groundwater environment. The quantification of groundwater-surface water interactions at the watershed scale requires upscaling. This study uses MIKE SHE, a coupled numerical model, to explore the seasonally and spatially dynamic nature of these interactions in the Cowichan Watershed on Vancouver Island, British Columbia, Canada. The hydrostratigraphy of the watershed is constructed using several datasets, including electrical resistivity tomography data. The calibrated model simulates a transition of the Cowichan River from mostly gaining within the valley, to losing stream near the coast where groundwater extraction is focused. Losing and gaining sections correlate with geological substrate. Recharge across the watershed accounts for 17% of precipitation. Climate change is projected to lessen snowpack accumulation in the high alpine and alter timing of snowmelt, resulting in higher spring river discharge and lower summer flows.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Diana M. Allen
Dirk Kirste
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

Risk to water security on small islands: a numerical modeling approach

Date created: 
2014-12-08
Abstract: 

The aim of this research is to characterise risk to water security for small islands. This is achieved by modeling the spatial and temporal impact from major stressors affecting water resources on small islands, and then evaluating the risk to water security through an integrated assessment framework. Numerical density-dependent flow and transport modeling is used to evaluate the response of the freshwater lens on Andros Island in The Bahamas to various climate change and human stressors including: sea level rise, changes in recharge, and increased pumping. SEAWAT models showed a reduction of freshwater lens volume by up to 24% under projected sea level rise and reduced recharge. The response time of the freshwater lens increased with stressor magnitude, resulting in a longer lens adjustment period. In addition, greater upconing was observed for pumping scenarios simulated under projected climate change conditions than under current conditions. The impact of a 2004 storm overwash event on Andros Island was simulated using HydroGeosphere. Results show that potable water is restored one month sooner when timely remedial actions are implemented; however, if delayed by four days or more, there is no improvement in recovery time. To extend the research more broadly, simulations of overwash for various island types observed worldwide were conducted. Dominant factors affecting freshwater lens response include vadose zone thickness and geologic heterogeneity, such as low or high permeability zones, whereas the dominant factor affecting freshwater lens recovery is recharge rate. A framework to characterise risk to water security was developed specific to an island hydrogeological setting. A freshwater lens susceptibility map was generated using the results of the numerical modeling. Hazard threats from climate change and human stressors (derived from numerical modeling and a land-use survey) were overlaid on the susceptibility map to represent vulnerability. Combining vulnerability with loss (or consequence) yielded a risk to water security map. High risk areas are largely concentrated within the developed areas near high chemical hazard activities, as well as along portions of the coastline. These maps were provided to local partners to inform water management policies and raise awareness about factors impacting water security.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Diana Allen
Department: 
Science:
Thesis type: 
(Thesis) Ph.D.

Architecture and Facies Analysis of Allomember F, Upper Cretaceous Horseshoe Canyon Formation, Drumheller, Alberta

Date created: 
2014-09-25
Abstract: 

Mixed-influence, marginal-marine deposits are typified by complex heterogeneous architectures that are challenging to model in the subsurface. Utilization of modern and outcrop analogs can serve to mitigate these limitations. Marginal-marine successions of the Horseshoe Canyon Fm near Drumheller, Alberta are well exposed in laterally continuous outcrops for 15 km down depositional dip and 3.5 km along depositional strike. This study uses 30 outcrop sections from Allomember F along the Red Deer River and Willow Creek and 4 subsurface cores to classify the deposits in terms of facies and to identify element complexes (EC). Depositional environments are interpreted to record a variety of marginal-marine, paralic, and coastal environments that include: wave-dominated, fluvial-influenced, tide-affected deltaic deposits (FA1); tidal-fluvial channels (FA2); wave-dominated, tide-influenced, fluvial-affected shoreface (FA3); and, delta plain/terrestrial deposits (FA4). The deposits are characterized using the WAVE Classification scheme. Using this process-based approach, FA1 is subdivided and categorized into two element complexes, namely a Fw (t) lobe complex and a Wf (t) mouthbar complex. FA2 is designated as a Ft channelized complex. FA3 is categorized as a Wtf beach complex. FA4 can be subdivided into multiple element complexes representing terrestrial deposits. Overall, the paleoshoreline forms a Wtf or Wft Element Complex Assemblage.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Dr. James MacEachern
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

Application of Photogrammetry to Estimates of Mine Pillar Damage and Strength

Author: 
Date created: 
2014-07-24
Abstract: 

The use of terrestrial photogrammetry for characterizing changes and damage in rock masses was investigated. Repeat photogrammetry surveys of hard rock pillars were conducted and compared to calculate material loss and damage. Damage measured from photogrammetry was then compared to stresses predicted by Displacement Discontinuity modelling and was found to agree well with current empirical damage-stress relationships. Observed damage profiles were also input into Boundary Element models to correlate predicted stress concentrations with locations of observed damage. Modelled stress concentration locations and magnitudes agreed well with observed damage locations and stress magnitudes from the literature, respectively. Geological structures were characterized from photogrammetry models and used to generate Discrete Fracture Networks, which in turn provided inputs for Distinct Element numerical models. The observed damage was then used to calibrate numerical models which, pending additional calibration, can be used to improve understanding of pillar strength.

Document type: 
Thesis
Senior supervisor: 
Douglas Stead
Davide Elmo
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Groundwater characterization and modelling in natural and open pit rock slopes

Date created: 
2014-05-29
Abstract: 

The stability of rock slopes is often compromised by the presence of groundwater in the discontinuities within the rock mass. Discontinuities form the major pathways for groundwater flow and result in seepage zones along slopes. The hydrogeological characterization of fractures is, hence, an important task in rock slope investigations. Nevertheless, most current techniques require direct access to the rock slope, which can often be severely limited due to access, safety and the limited coverage of survey methods. In an attempt to both complement and overcome existing limitations of current methods, the present research makes use of remote sensing techniques to implement a window mapping approach to allow for the collection of structural and seepage information over a wide spatial area. Photogrammetry, ground based LiDAR and Infrared Thermography (IRT) are discussed. Research is also undertaken investigating continuum, discontinuum (distinct element model) and lattice-spring scheme modelling applied to assess the effect of groundwater on large open pit rock slope stability. Fluid flow within a fractured rock mass occurs as a coupled process where the flow field is influenced by the stress field and changes in stress resulting in changes in pore water pressures within the rock mass. The key findings gathered through this research highlight the importance of considering the use of coupled field and state-of-the-art remote sensing techniques in the characterization of seepage areas on high engineered and natural rock slopes. Similarly, numerical codes provided meaningful ways to account for the effect of incorporating groundwater in slope stability analysis. The continuum code, Phase 2, is shown to be suitable for simulating non-fracture controlled slope analysis. Nevertheless, limitations exist when groundwater flow is mainly affected and controlled by the fractures defining the rock mass. The conventional UDEC code is shown to be useful at providing information on the effect of the inclusion of pore water pressures, UDEC-Voronoi/Trigon is demonstrated to be an innovative and meaningful technique to account for the development of stress-induced brittle fracturing. The newly developed lattice-spring Slope Model is proven to be a useful means to assess the role of groundwater conditions on slope instability.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Doug Stead
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.