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

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The influence of bedrock geology on glacier dynamics in the St. Elias Mountains, Yukon, Canada

Author: 
Date created: 
2019-11-27
Abstract: 

Glacier surges are characterized by order-of-magnitude increases in flow that can be sustained for months to years, facilitated by a dramatic increase in basal water pressure that permits rapid sliding. An explanation for the non-random geographical distribution of surge-type glaciers and the underlying causes of surges remain the source of speculation. Glacier surges are dynamic end-members of glacier behaviour that showcase fundamental processes operating under all warm-based glaciers. Providing an explanation for the distribution and mechanisms of surging will allow us to better predict the role and responses of glaciers in a warming climate. The primary objective of this research is to understand the relationship between geological substrates and surge-type glaciers. A second objective is to understand the more general relationships between bedrock properties and the physical and chemical processes of glacial erosion. Using data from 11 surge-type and 9 non-surge-type glaciers in the St. Elias Mountains of Yukon, Canada, I investigate geological variables that represent system inputs, such as bedrock mineralogy and fracture characteristics, and system outputs such as meltwater chemistry and the grain size and mineralogy of proglacial river suspended sediments. I find that glacier surging is correlated with bedrock fracture spacing and the grain size of suspended sediments. I propose that bedrock fracture spacing controls the rate of clast production, and therefore the distribution of a clast-rich till-transition zone, which provides the excess friction necessary for the development of an ice reservoir prior to surging. Within a given climate envelope and mass-balance regime, this conceptual model can help to explain the geographical distribution of surge-type glaciers. Through a mineralogical analysis of electrically fragmented bedrock samples and proglacial suspended sediment samples, I observe that primary minerals are comminuted to sub-micron sizes, and grain rounding appears to be shaping medium-silt size grains and smaller. Finally, I find that chemical alteration of sediment and clay mineral precipitation could be mechanisms to explain the characteristically low silica in glacier meltwaters. Through this work, I have highlighted some of the ways in which the geological substrate can drive subglacial physical and chemical erosion and thus, glacier dynamics.

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

Surficial geology, stratigraphy, and placer deposits of the Ruby Range, Yukon Territory

Author: 
Date created: 
2019-06-07
Abstract: 

The Quaternary history of the central Ruby Range, southwest Yukon, was studied through 1:50,000 scale surficial mapping and stratigraphic analysis. Stratigraphy in Gladstone Creek provides evidence for at least two glaciations of the Cordilleran Ice Sheet’s (CIS) St. Elias lobe, during marine oxygen isotope stages 2 and 4. Significant ice was produced from cirques and ice caps within the Ruby Range that likely contributed to the CIS incursion within Gladstone Creek. Advances from Ruby Range cirques appear to have preceded CIS advances and are preferentially preserved in stratigraphy due to lower base-levels associated with their advance. Stratigraphic units are constrained by tephrochronology, luminescence, and radiocarbon dating. 10Be dating on erratics suggests alpine glacier readvances occurred in Raft and Rockslide creeks at 13.7 ± 0.9 ka, significantly later than the last glacial maximum of the CIS. Placer deposits in Gladstone Creek have been reworked by repeated cycles of glaciation resulting in complex stratigraphic distributions, generally occurring on bedrock and false bedrock surfaces. Gold appears to be sourced from both epithermal mineralization in Kluane schist, as well as gold-rich porphyry mineralization in the Ruby Range batholith.

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

The characterization of slope damage using an integrated remote sensing-numerical modelling approach

Author: 
Date created: 
2019-05-27
Abstract: 

The stability of slopes is controlled by geological structures, lithology, rock mass quality, and hydrogeological conditions. Additionally, the occurrence of exogenic and endogenic processes may weaken the rock mass forming the slope, promoting instability. Slope deformation is associated with the formation of a range of internal and external features, such as tension cracks, rock mass dilation, and rockfall, referred to as “slope damage”. In this research, state-of-the-art remote sensing techniques, including terrestrial and airborne laser scanning, digital photogrammetric methods, high-resolution photography, infrared thermography, and hyperspectral imaging, are employed to characterize slope damage features both spatially and temporally. New innovative measures of slope damage are introduced. Processes and mechanisms controlling the formation and distribution of slope damage are highlighted at selected major landslides using advanced numerical modelling techniques, including distinct element, hybrid finite-discrete element, and lattice-spring scheme methods. Innovative uses of remote sensing data as a constraint for 3D modelling of slope damage are presented. This research clearly demonstrates that several geological factors control the formation, distribution, and evolution of slope damage, with the results being summarised in a slope damage interaction matrix format. It is clearly shown that the characterization of slope damage, combined with remote sensing datasets and numerical modelling results, allows reinterpretation of slope deformation and failure mechanisms of selected landslides in rock and soil. The recognition and importance of interaction between kinematics, geological structures and damage on the long-term evolution of the Downie Slide and Hope Slide (BC) is clearly demonstrated. The important role of brittle fracture propagation on the kinematics of the 2014 San Leo landslide (Italy) on the 2014 slope failure is highlighted. The geomorphic controls on external spatio-temporal slope damage at the Ten Mile Slide (BC) is emphasised using new damage measures. This research highlights the need to include slope damage mapping techniques as a standard procedure in rock slope characterization, in order to obtain important insights on the mechanisms and processes that affect the stability, deformation, and failure of rock slopes.

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

The role of englacial hydrology in the filling and drainage of an ice-dammed lake, Kaskawulsh Glacier, Yukon, Canada

Author: 
Date created: 
2019-03-06
Abstract: 

Catastrophic drainage of glacier-dammed lakes can have significant downstream impacts. The role of the little-studied englacial hydrological system is investigated during the filling and drainage of an ice-marginal lake dammed by the Kaskawulsh Glacier in Yukon, Canada. Geophysical and hydrometeorological instruments were deployed to monitor the hydrology and dynamics of the lake--glacier system. Water-balance calculations reveal that of the ~44.1 million cubic metres of water in the catchment at peak lake level, the subglacial and englacial reservoirs store approximately 55% and 22%, respectively, compared to 23% in the subaerial lake. Abrupt changes in ice-shelf uplift rates, associated with fracturing and faulting, are linked to the redistribution of englacial water (1.6--6.6% estimated water content) based on borehole water-pressure and radar reflection-power data. Characterizing the dynamic coupling of the reservoirs, and the abrupt nature of connections between them, represents an advance in our conceptual understanding of glacier lake outburst floods.

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

Time-lapse gravity monitoring at Cotopaxi volcano, Ecuador: A glimpse inside a restless colossus

Date created: 
2019-02-26
Abstract: 

Cotopaxi, a glacier-clad stratovolcano located in Ecuador, showed signs of unrest in April 2015, which ramped up until August 14, 2015, with the advent of phreatomagmatic explosions. Time-lapse gravity measurements started at Cotopaxi volcano in June 2015. Minor gravity changes were detected prior to eruptive activity, however, the largest gravity variations at Cotopaxi were measured between October 2015 and March 2016, as other geophysical parameters reached background levels. Inverse modelling using GPS data pointed towards a deep intrusion prior to eruptive activity, while inverse modelling of post-eruptive gravity data fit with changes in the hydrothermal system. A deep magmatic source intruded between April and August 2015, leading to measured deformation and seismicity, while an inferred shallow source rose from depth and interacted with the hydrothermal system, causing the phreatomagmatic activity. Hydrothermal fluids were pushed from a deep aquifer into a shallow perched aquifer, and caused time-lapse gravity variations.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Glyn Williams-Jones
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

The Eastern Flank: Predicting the Architecture of the McMurray Formation Beyond its Subcrop Edge

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2018-07
Abstract: 

Lower Cretaceous sediment was delivered to the McMurray Sub-Basin, probably via a continental-scale drainage system with headwaters in the Canadian Shield, Appalachians, and Cordillera of North America. Towards the mouth of the continental-scale drainage, a series of tributaries drained the Canadian Shield, although the number, scale, and position of tributaries is poorly constrained. Herein, the McMurray paleodrainage system is mapped from the main fairway east towards the sparsely drilled and erosionally truncated subcrop edge. Linear and exponential regression is then used to map the McMurray Fm to its theoretical eastern extent. Interpretations provided in this study indicates Assiniboia Valley, trunk valley of the McMurray Fm drainage, is not substantially wider than currently mapped, and the currently identified axis of Assiniboia Valley is accurate. However, the tributary network entering Assiniboia Valley from the Canadian Shield is complex with three main tributaries identified: Firebag, Buffalo River, and Choiceland tributaries.

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

Refining the chronostratigraphy of the Lower Nanaimo Group, Vancouver Island, Canada, using detrital zircon geochronology

Author: 
Date created: 
2018-12-17
Abstract: 

Convergent-margin basins (CMBs) are rich in broadly coeval detrital zircon (DZ) owing to the proximity of active magmatic belts. Consequently, DZ geochronology can be employed to assess the utility of stratigraphic frameworks developed for these basins. This study uses DZ data to assess the utility of lithostratigraphy developed for the Cretaceous-aged lower Nanaimo Group in the Georgia Basin, Canada. Results show that the basal lithostratigraphic unit of the Nanaimo Group, the Comox Formation, comprises strata that are neither time correlative nor genetically related. The three lithostratigraphic units directly overlying the Comox Formation (Haslam, Extension, and Protection formations) comprise strata with similar genetic affinities, indicating that deposition of these units was not entirely sequential, and contemporaneous in some locales. Further, sediment provenance evolved through time, which the existing lithostratigraphic framework does not reflect. This work demonstrates that DZ geochronology can effectively test the utility of stratigraphic frameworks in CMBs.

Document type: 
Thesis
Supervisor(s): 
Shahin E. Dashtgard
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Early evolution of a forearc basin: Georgia Basin, Vancouver Island, Canada

Author: 
Date created: 
2018-12-18
Abstract: 

The Late Cretaceous lower Nanaimo Group was deposited in the forearc Georgia Basin of BC, Canada along the western margin of the Canadian Cordillera, and records its initiation and early depositional evolution. Nanaimo Group strata are currently subdivided into 11 lithostratigraphic units, which are identified based on lithology, texture (i.e., dominantly coarse- or fine-grained), and position relative to the basal nonconformity and to one another. Paleotopography on the basal nonconformity, however, ensures that these lithostratigraphic units are not time correlative, and hence, cannot reliably be used to reconstruct basin evolution. Herein, transgressive-regressive sequence stratigraphy is employed to construct a stratigraphic framework for the lower Nanaimo Group. Eight depositional phases are identified in the lower Nanaimo Group. Depositional phases are separated by flooding surfaces, regressive surfaces, or unconformities. The stratigraphy of the lower Nanaimo Group reflects net transgression, manifested as an upwards transition from braided fluvial conglomerates through to marine mudstones.

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

An investigation into the time dependent deformation behaviour of open pit slopes at Gibraltar Mine, BC, Canada

Author: 
Date created: 
2018-12-18
Abstract: 

Open pit slope instabilities experience a sequence of decelerating deformation events following changes in stress state due to blasts or mining. These deformation events are poorly understood. This thesis uses large databases of specific energy and slope radar monitoring data to characterise five slope instabilities. Eight different rheological and empirical curve-fitting models are applied to 24 deformation events to identify which model best approximates observed deformation. The best-performing model, the Fractional Maxwell model, is then applied to nearly 200 deformation events identified from the five slope instabilities. The resulting model parameters α, fractional viscosity, and A, magnitude of the response, are tracked and compared with deformation history, instability size and geometry, and blast size and location. Slope instabilities exhibit increasingly viscous behaviour with deformation as damage accumulates within the rock mass. The magnitude and likelihood of deformation events correlate with the proximity of the stress change to critical geological structures.

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

Sedimentological and ichnological characterization of small- and large-scale channel IHS in the Middle McMurray Formation of the Central-C area, McMurray Sub-Basin, Alberta

Author: 
Date created: 
2018-12-11
Abstract: 

The Lower Cretaceous McMurray Formation is interpreted as a brackish-water, tidally influenced estuarine complex. The study area encompasses Townships 90-95, Ranges 10-14W4 in northeast Alberta. Facies analysis of 41 cored wells led to the identification and differentiation of large- and small-scale lateral accretion IHS associated with tidal-fluvial channels. Five sedimentary facies are assembled into four recurring facies associations to characterize these channel systems. Sedimentological and ichnological characteristics point to elevated physico-chemical stress in most large-scale channel successions, interpreted to be the consequence of carrying the bulk of the fluvial discharge through these trunk channel systems. By contrast, small-scale channels display less evidence of physico-chemical stress indicating they carried little fluvial flow. Abandoned channel deposits likewise show reduced paleoenvironmental stress. This study suggests that the deposits of small-scale channels and abandoned channels are the most suitable for assessing the degree of marine influence in the study area.

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