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

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Optical dating of stabilized parabolic dunes, Savary Island, British Columbia

Date created: 
2017-06-13
Abstract: 

Research has shown that the south coast of British Columbia (BC) has experienced changes in relative sea level and climate since deglaciation (~15 ka ago); however, there has been little study of the landscape’s response to these changes. On Savary Island, in the Strait of Georgia, there exist large parabolic dunes that are unique to the region. These dunes are stabilized, supporting mature forest growing in well-developed soil, and they contain eroded palaeosols indicating that their formation was punctuated by periods of episodic stabilization and soil formation. Optical ages from K-feldspar indicate that dune formation began prior to 7.69 ± 0.71 ka and stabilized by about 5.47 ± 0.36 ka ago when relative sea level lowering was slowing and climate was becoming cooler and moister. Periods of landscape stability during dune formation were brief, probably lasting only a few hundred years.

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

Characterizing Recharge to Fractured Bedrock in a Temperate Climate

Date created: 
2017-05-16
Abstract: 

Fractured bedrock aquifers can have large seasonal water table fluctuations due to their low storage capacity. This study uses a land surface – subsurface model, MIKE SHE, to investigate the spatial and seasonal rainfall-runoff-recharge dynamics on Gabriola Island, in a temperate region of British Columbia, Canada. The model results suggest that recharge averages 20% of the annual precipitation, occurring dominantly over 70% of the island, typically at higher elevation. Perennial seepage areas are simulated over 4% of the island, and are generally confined to breaks in slope in low topography areas. The high water table in late fall to early spring causes both seepage and saturated overland flow to contribute to more runoff. Increases in precipitation due to climate change leads to increased runoff (+36% to +40%) and recharge (+8% to +10%) relative to today. Recharge changes are most significant in winter (+13% to +16%), compared to summer (-3% to -4%).

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

Channel scour on temperate alluvial fans in British Columbia

Date created: 
2017-06-01
Abstract: 

This thesis examined the morphometric controls on channel scour depth on temperate fans in British Columbia, Canada. Scour measurements and morphometric variables were catalogued for 116 fans and used to develop a predictive multivariate equation. Stepwise regression and multimodel inference were used to rank the importance of each morphometric variable and to develop the final predictive models. Watershed area, fan gradient, and fan relief were identified as the most important variables that contributed to channel scour. The predicted scour values explained approximately half of the variance in the observed scour measurements, with the largest deviations observed at higher values. A case study of a debris flow event at Neff Creek demonstrated that intense fan scour can amplify the final deposit volume and cause significant damage on the distal fan. The results of this study can be used to prioritize scour hazard assessments for infrastructure development on fans.

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

Glacial History and Landform Genesis in the Lac de Gras Area, Northwest Territories

Date created: 
2017-01-27
Abstract: 

The Quaternary geology of the Lac de Gras area was studied by 1:20 000 surficial geology mapping of 770 km2 and investigating the genesis of enigmatic landforms. Three distinct flow directions of the Laurentide Ice Sheet are recorded: flow to the southwest, then west, and finally to the west northwest. Digital mapping with high-resolution orthoimagery and a 30 cm lidar DEM provides insight into the deglacial history. ‘Subglacial meltwater corridors’ are prominent in the area. These are tracts that roughly parallel the final ice-flow direction, where basal till has been eroded, bedrock is exposed, and glaciofluvial sediments have been deposited; enigmatic, glaciofluvial mounds composed of sandy diamicton are common. These mounds have highly variable morphologies and occur in groups. They are typically 50 m wide and rise up to 15 m above the surrounding topography. Subglacial meltwater corridors and enigmatic mounds likely formed when supraglacial lakes drained catastrophically during deglaciation.

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

Developing fluorite as a geochemical pathfinder mineral using globally reported REE-Y contents

Author: 
Date created: 
2017-05-12
Abstract: 

Discrimination diagrams have been created to begin development of fluorite as a geochemical pathfinder mineral based on a compilation of approximately 630 trace-element analyses (ICP-MS, ICP-AES, LA-ICP-MS, NAA, INAA) of fluorite from 183 deposits/localities from nearly 60 regions world-wide. A classification scheme of primary mineralization environments was determined to describe potentially economic deposits in which fluorite commonly occurs as listed here in order of representation quality: 1.) hydrothermal/epithermal vein/replacement in igneous hosts, 2.) MVT, 3.) vein/replacement in carbonate hosts, 4.) carbonatite-related, 5.) vein/replacement in metamorphic hosts 6.) SEDEX, 7.) skarn, 8.) greisen, 9.) intrusion-related Mo, 10.) cryolite, 11.) peralkaline silicate igneous rock, 12.) vein/replacement in sedimentary hosts, 13.) rare-metal pegmatite, 14.) granite-related U, and 15.) IOCG deposits. Discrimination diagrams were created using 67th percentile contours of scatter datafields per primary mineralization environment generated using ratios of REE-Y data and equations created by discriminant projection analyses. These diagrams were tested using FUS-ICP/MS analyses of fluorite handsamples sourced from eight North American deposits with predetermined primary mineralization environments assigned from literature review. Correct assignations were confidently returned for half of eight sampled deposits using 11 analyses of samples and less confidently returned for another quarter. Though the exact mechanisms controlling trace-element partitioning in fluorite are poorly understood, this study provides an improved method to discriminate between fluorite-bearing deposits.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Daniel Marshall
Derek Thorkelson
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Guidance for debris-flow and debris-flood mitigation design in Canada

Author: 
Date created: 
2017-08-03
Abstract: 

Steep creek hazards such as debris flows and debris floods pose considerable risks to mountain communities and infrastructure. In Europe and Japan, centuries of experience in steep creek hazard mitigation have produced substantial practical design knowledge. By comparison, Canadian professionals have limited experience with engineered debris-flow and debris-flood risk management. This thesis aims to close the knowledge gap through three distinct approaches. First, local and international design practices are reviewed, to highlight the unique challenges facing Canadian practitioners. Second, I present a design approach that aims to improve the state of practice in Canada by creating a repeatable and transparent workflow. Finally, a series of case studies emphasize the applicability of decision analysis and integrated river management for debris-flow and debris-flood mitigation design. The results of this study can be used to inform steep creek risk management efforts in Canada.

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

Numerical investigations of subglacial hydrology as a direct and indirect driver of glacial erosion

Author: 
Date created: 
2017-05-26
Abstract: 

Glaciers shape high altitude and latitude landscapes in numerous ways. Erosion associated with glacial processes can limit the average height of mountain ranges, while creating the greatest relief on Earth and shaping the highest mountain peaks, but glaciers can also shield pre-existing topography. Glacial erosion processes, though still enigmatic, are central to the evolution of landscapes, particularly since the onset of the Pleistocene. Glacial erosion comprises three fundamental processes: (1) abrasion, (2) quarrying and (3) the direct action of subglacial water flow in sediment transport and bedrock erosion. Glacier sliding and the hydro-mechanical conditions at the ice--bed interface drive erosion processes, and are themselves controlled by the morphology and state of the subglacial drainage system. Although widely acknowledged, the direct and indirect controls of subglacial water flow on glacial erosion have been largely neglected in previous studies. This thesis focuses on exploring these controls using numerical models with an emphasis on sub-annual to annual timescales. This work has three primary objectives: (1) to investigate how the state and morphology of the subglacial drainage system indirectly drive abrasion and quarrying, (2) to devise the first model of direct bedrock erosion by subglacial water flow and (3) to develop a framework for sediment transport in subglacial channels over a rigid bed. The results show that well-known seasonal variations in subglacial hydrology drive patterns of glacial erosion. Abrasion is favoured where the drainage system is the most dynamic, whereas quarrying calculated using a recently published law is hindered; the latter result is at odds with previous theories. Direct erosion by subglacial water flow can explain bedrock channel excavation, but the resulting erosion rates remain negligible compared to expected basin-wide glacial erosion rates. The models predict a bottleneck in sediment transport near the glacier terminus that is inherent to channel dynamics. The resulting sediment accumulation provides a process-based explanation for esker deposition, and could shape proglacial sediment yields. In focusing on spatial and temporal scales commensurate with subglacial processes, this study challenges some of the common assumptions made in glacial erosion studies and provides a starting point for refining models of landscape evolution.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Gwenn E. Flowers
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.

Tectonometamorphic history of mid-crustal rocks at Aishihik Lake, southwest Yukon

Date created: 
2017-04-12
Abstract: 

Field mapping, petrography, thermodynamic modelling, and U-Pb (monazite and zircon) and 40Ar/39Ar geochronology reveal the tectonometamorphic history of polydeformed, amphibolite-facies rocks near Aishihik Lake, Yukon. Detrital zircon U-Pb ages suggest that these rocks are correlative to the Snowcap assemblage of the Yukon Tanana terrane. A penetrative regional foliation (S1) developed during the late Paleozoic, as S1 is cross-cut by a late Permian pluton. Permian plutons also exhibit less strain than Mississippian plutons near Aishihik Lake. The main foliation (S2) reflects west-verging, ductile shear (D2) during amphibolite facies metamorphism. Dating of Low-Y metamorphic monazite constrains the timing of D2 to 200-190 Ma. Peak T and P during D2 were 640-650 °C and ~7 kbar, respectively. High-Y monazite ages date regional decompression at ca. 188 Ma. 40Ar/39Ar thermochronology results indicate regional cooling through muscovite closure at ca. 175 Ma, whereas ca. 126 Ma biotite may reflect cooling following east-verging Jura-Cretaceous deformation (D3).

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

Optical Dating Studies of southeastern Patagonian Sand Wedges in Chile and Argentina

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2016-04-18
Abstract: 

The purpose of this study was to establish a suitable single aliquot regenerative dose (SAR) optical dating protocol for K-feldspar sediments in southeast Patagonia using radiocarbon-dated Holocene dune sediments at Lago Arturo. The established protocol was then applied to sand wedge sediments found in the region in order to date periods of permafrost and to provide limiting ages on glaciation. The suitable SAR protocol incorporates a 200oC/10 s preheat for both the additive-dose and test dose measurements, a hot (290oC) bleach step at the end of each SAR cycle to reduce recuperation, and measurement of the stimulated luminescence at 50oC. A select number of sand wedges found throughout the region were dated using the established protocol. Those that yielded reliable ages date to the last glaciation. Some sand wedges provided older optical ages, however, more testing is required to determine if these ages are accurate.

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

Characterization of blast damage in rock slopes: An integrated field-numerical modeling approach

Author: 
Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2016-07-04
Abstract: 

Consideration of blast damage in rock slope stability has been a challenging task in rock mechanics because blasting results depend on several factors that can lead to different forms of damage. Currently, it is not clear on how to consider blast damage in rock slopes. This thesis investigates the occurrence of blast damage in rock slopes using an integrated field investigation, remote sensing and numerical modelling approach. A framework for defining blast damage in the field and using remote sensing data was developed to provide the input for a blast damage model which can then be used either for numerical analysis or understanding the occurrence of blast damage features in the field. Results of field investigation and numerical simulations show that blast damage on the rock slope surface varies depending on the rock mass quality. Blast fracturing increases with decrease in rock mass quality. Observations on exposed joint surfaces in open pit slopes indicate that the blasting process has induced varying forms of damage on these surfaces. Finite-discrete element numerical modelling of blast induced damage indicates that blast damage develops in different forms from the slope surface. The simulated blast damage zone varied from complete blocks (fully connected blocks), partially connected blocks, dilation and undamaged zone. The extend of the blast damage increased with decrease in strength of the rock. A stronger rock mass show less blast damage thickness compared to a weaker rock mass. Results show that blast damage features such as blast fracture, damage along the joint surface and extension of joints all influence slope stability.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Doug Stead
Davide Elmo
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.