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

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Geophysical investigations of magma plumbing systems at Cerro Negro volcano, Nicaragua

Date created: 
2013-11-27
Abstract: 

Cerro Negro near Léon, Nicaragua is a very young (163 years), relatively small basaltic cinder cone volcano that has been unusually active during its short lifespan (recurrence interval 6-7 years), presenting a significant hazard to nearby communities. Previous studies have raised several questions as to the proper classification of Cerro Negro and its relation to neighboring Las Pilas-El Hoyo volcano. Analysis of Bouguer gravity data collected at Cerro Negro has revealed connected positive density anomalies beneath Cerro Negro and Las Pilas-El Hoyo. These findings suggest that eruptions at Cerro Negro may be tapping a large magma reservoir beneath Las Pilas-El Hoyo, implying that Cerro Negro should be considered the newest vent on the Las Pilas-El Hoyo volcanic complex. As such, it is possible that the intensity of volcanic hazards at Cerro Negro may eventually increase in the future to resemble those pertaining to a stratovolcano.

Document type: 
Thesis
Senior supervisor: 
Glyn Williams-Jones
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Evolution of the Coast Cascade Orogen by Tectonic Thickening and Magmatic Loading: The Cretaceous Breakenridge Complex, Southwestern British Columbia

Author: 
Date created: 
2013-09-18
Abstract: 

A model for the tectono-magmatic mid-Cretaceous (110-80 Ma) evolution of the southern Coast belt is proposed. The first magma pulse represented by the 107-100 Ma Breakenridge pluton intruded within a magmatic arc as a set of shallow sills. It was initially buried by orogen-parallel contraction, followed by the emplacement of the 96-94 Ma Snowshoe pluton, which belongs to the second magma pulse. The Snowshoe pluton was emplaced by similar mechanisms in structurally higher levels of the crust. Orogen-normal compression was the final mechanism for deep burial and attainment of peak metamorphic conditions (500-680°C at 6.5-10.3 kbar) of the study area between 91-86 Ma. Following orogen-normal contraction and regional folding, oblique right-lateral strike-slip shearing occurred while rocks were in a ductile environment. The third magma pulse (86-84 Ma) was synchronous with the late stages of high-grade metamorphism and early stages of oblique strike-slip movement.

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

Palynology and geochemistry of sediments in the tidally influenced lower Fraser River, British Columbia

Date created: 
2013-08-29
Abstract: 

In the tidally influenced Fraser River and adjacent Strait of Georgia (SoG), Canada, palynological and carbon isotope (δ13Corg) signatures of channel-margin sediments are compared to environmental parameters (e.g., substrate grain size, water salinity) in order to establish how these vary across the tidal-fluvial transition. Palynological assemblages in both the Fraser River and SoG (delta front and prodelta) are dominated by tree pollen, which comprises between 85% and 95% of all assemblages. Relative abundances of marine dinocysts are markedly low, and the maximum abundance of dinocysts is 6.8% or 1,023 cysts g-1 of sediment in samples recovered from the prodelta. Dinocyst abundances do not exceed 2% of the total palynological assemblage in the Fraser River, and the number and diversity of dinocysts gradually decreases landward. Organic carbon-13 enrichment values range from -26.55‰ in sediments deposited in the freshwater-tidal reach of the Fraser River, to -21.08‰ in prodeltaic sediments. The δ13Corg and palynological signatures of river, delta front, and prodelta sediments indicate a dominance of terrestrially sourced organic matter regardless of brackish-water and tidal influence on sediment deposition.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Shahin Dashtgard
Rolf Mathewes
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Simulation of failure mechanisms around underground coal mine openings using discrete element modelling

Author: 
Date created: 
2013-09-06
Abstract: 

Roof failure has always been a major concern in underground coal mine roadways. Understanding the failure mechanism of roadway roofs is important for improving the safety of underground coal mines and reducing economic loss. In this research, a numerical modelling methodology named UDEC Trigon in 2D and 3DEC Trigon in 3D and based on a discrete element framework is developed to model rock mass behaviour, with a particular focus on the damage process including generation and propagation of fractures, and heavy dilation in the post-peak failure stage. Simulation of compression and Brazilian tests indicates that the methodology can capture different failure mechanisms under verying loading conditions. The UDEC Trigon is then used to investigate shear failure mechanism in roadway roofs. The results suggest that shear cracking plays a dominant role in the roof shear failure. Rock bolts can aid in ensuring the retention of more rock bridges which is critical to the roof stability. Cutter roof failure, which is a three-dimensional roadway rock failure mechanism, is studied using both PFC3D and 3DEC Trigon. The 3D models explicitly capture the cutter roof failure process and found that incorporating bedding planes and corss joints results in a more distinct cutter failure. Roadway squeezing failure mechanism is studied using the UDEC Trigon approach. The results show that the UDEC Trigon approach is able to reproduce the large dilation due to fracturing of rock mass surrounding a roadway under two distinct situations: high mining-induced stress and strength degradation of moisture sensitive rocks. In addition, the UDEC Trigon approach is used to simulate the progressive caving process of a longwall panel of coal. It is found that compressive shear failure, rather than tensile failure, is the dominant failure mechanism in the strata above the goaf. A further demonstration of the potential of UDEC Trigon in capturing roadway failure is presented as a case study of a roadway driven adjacent to unstable goaf in the Wuyang Coal Mine. The case study reveals that the combination of Synthetic Rock Mass (SRM) and UDEC Trigon is able to evaluate failure mechanisms in underground coal mines.

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

Quaternary geology in part of the McLeod Lake map area (NTS 093J), central British Columbia

Date created: 
2012-11-02
Abstract: 

The Quaternary geology in part of the McLeod Lake map-area was studied through the production and analysis of 1:50 000-scale terrain maps and the examination of stratigraphic exposures and landforms. The surficial geology is dominated by thick, streamlined till that thins where relief is high. Glaciofluvial outwash and ice-contact deposits occur throughout the area and extensive glaciolacustrine deposits blanket low-lying regions. The glacial stratigraphic record spans the Fraser Glaciation and is represented by a sequence of advance glaciolacustrine sediments, till and retreat glaciolacustrine and glaciofluvial sediments. Ice initially flowed into the study area from the northwest and retreated before the arrival of ice from the west and south. Ice-flow during the glacial maximum was northeast and transitioned to the east during deglaciation. Ground penetrating radar suggests that post-glacial aeolian activity was brief. Optical dating on K-feldspar from aeolian material suggests this activity occurred around 9.35 ± 0.64, 9.94 ± 0.77 and 13.3 ± 1 ka and provides minimum ages for ice retreat.

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

Integrated ichnology and sedimentology of mixed river- and wave-influenced delta complexes, Upper Cretaceous basal Belly River Formation, central Alberta, Canada

Date created: 
2013-05-16
Abstract: 

Marine-generated bounding discontinuities subdivide the basal Belly River cycles into 3 allomembers (D, E, and G). Detailed sedimentological and ichnological analysis of allomembers D and E of the Upper Cretaceous basal Belly River Formation (central Alberta) reveals 13 discrete facies. Sedimentary facies are grouped into 6 mappable facies associations. Depositional environments are interpreted to record a variety of marginal-marine, paralic, and coastal environments, including: river-dominated, storm-influenced deltas (FA1); storm-dominated, mixed river- and wave-influenced deltas (FA2); fluvial channels (FA3); fluvio-estuarine distributary channels (FA4); marine-influenced, lower delta plains (FA5); and delta/coastal plains (FA6).Based on the integration of data from cored intervals, multiple dip- and strike oriented cross-sections, and net-sand isopach maps; no lateral variations in facies distribution, consistent with the asymmetric delta model, are identified. Correlations indicate that the deposits of Allomember D are exclusively linked to FA1 successions, whereas the deposits of Allomember E are exclusively linked to FA2 successions.

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

Sedimentological and paleomagnetic study of glacial Lake Missoula lacustrine and flood sediment

Date created: 
2013-04-04
Abstract: 

During the Fraser Glaciation (marine oxygen isotope stage 2), floods from ice-dammed glacial Lake Missoula affected large parts of Washington and Oregon. Flood deposits are interbedded with glaciolacustrine sediment in glacial Lake Columbia, and occur as thick slackwater sediments in southern Washington and in the Willamette Valley, Oregon. This thesis examines some of the issues surrounding this flooding, such as how many times glacial Lake Missoula emptied, whether glacial Lake Missoula is the only source of the floods, and the timing of these events. The sedimentology and stratigraphy of a new section of rhythmically stratified glaciolacustrine sediment in the glacial Lake Missoula basin confirms that the ice dam failed at least a few dozen times, exposing the lake bottom. Current indicators and clast lithologies of flood sediments in glacial Lake Columbia indicate that glacial Lake Missoula was the source of these flood beds. Additionally, rock magnetic studies identify hematite in fine-grained flood sediment that settled out of the water after the high-energy floodwaters had passed. The source of the hematite is the Belt-Purcell Supergroup in Montana, which supplied sediment to glacial Lake Missoula. Optical ages, a radiocarbon age, and paleomagnetic secular variation records help to constrain the timing of glacial Lake Missoula flooding. Optical dating was successful on three samples of fluvial sand deposited during initial filling of glacial Lake Missoula and on loess deposited above Mount St. Helens set S tephra, which is a time-stratigraphic marker found in glacial Lake Missoula flood deposits. One sample of fossil plant detritus was found below at least 37 flood beds in glacial Lake Columbia. Lastly, four paleomagnetic secular variation records constrain the timing of glaciolacustrine units in glacial Lake Missoula and flood beds in glacial Lake Columbia and the Willamette Valley. All glacial Lake Missoula units and flood units studied in this thesis date to the later part of the Fraser Glaciation, between ~14.2 and 11.6 14C ka BP.

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

Seasonal controls on the development and character of inclined heterolithic stratification in a tide-influenced, fluvially dominated channel, Fraser River, Canada

Date created: 
2011-03-17
Abstract: 

Inclined heterolithic stratification (IHS) is developed on an in-channel bar in the tide-influenced, fluvially dominated reach of the Fraser River, British Columbia, Canada. The vertical bar succession is characterized by a fining-upward profile with an increase in mud-bed thickness and content, from the shallow subtidal to the upper intertidal zone. There is an increase in the number of mud beds as well as their lateral continuity from the upstream to the downstream side of the bar. Sediment deposition is seasonally controlled, wherein sand deposition occurs during periods of high discharge (snowmelt-induced freshet), and mud is deposited during low discharge (ambient flow conditions). The seasonal cyclicity in sediment deposition is also observed in the ichnological character of the IHS. Mud beds are typically moderately to pervasively bioturbated (Bioturbation Index (BI) 2-5), and sand beds exhibit little to no bioturbation (BI 0-2).

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

Distributed energy-balance glacier melt-modelling in the Donjek Range of the St. Elias Mountains, Yukon Territory, Canada: model transferability in space and time

Date created: 
2010-10-20
Abstract: 

Modelling melt from glaciers is crucial to assessing regional hydrology and eustatic sea-level rise. To investigate melt-model transferability, a distributed energy-balance melt model (DEBM) is applied to two glaciers of opposing aspects in the Donjek Range of the St. Elias Mountains, Yukon Territory, Canada. An analysis is conducted in four stages to assess the transferability of the DEBM in space and time: (1) locally derived model parameter values and meteorological forcing variables are used to assess model skill; (2) model parameter values are transferred between glacier sites and between years of study; (3) measured meteorological forcing variables are transferred between glaciers, using locally derived parameter values; (4) both model parameter values and measured meteorological forcing variables are transferred from one glacier site to the other, treating the second glacier site as an extension of the first. The model has high transferability in time, but has limited transferability in space.

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

Modelling the impacts of climate change on groundwater: A comparative study of two unconfined aquifers in southern British Columbia and northern Washington State

Author: 
Date created: 
2005
Abstract: 

A methodology is developed for linking climate and groundwater models to investigate future impacts of climate change on groundwater resources using two case study sites of unconfined aquifers in southern British Columbia and northern Washington State. One semi-arid site is compared with one wet coastal site. The two groundwater systems differ in river-aquifer interactions, recharge, aquifer heterogeneity, scale, and groundwater use. Climate change scenarios from the Canadian Global Coupled Model 1 model runs for 1961-2000,2010-2039,2040-2069 and 2070-2099 are downscaled to local conditions, modelled at daily time scales using a stochastic weather generator, and applied to the spatially-distributed infiltration model. At one site the basin-scale runoff is also downscaled to predict river discharge and river-aquifer interactions in future climates. The impacts of predicted climate change on the groundwater system for each site are modelled in three-dimensions using Visual MODFLOW. Results and methodologies are compared and discussed.

Document type: 
Thesis
File(s): 
Department: 
Department of Earth Sciences - Simon Fraser University
Thesis type: 
Thesis (M.Sc.)