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

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Numerical modeling of highly saline wastewater disposal in Northeast British Columbia

Author: 
Date created: 
2018-04-26
Abstract: 

Dense, saline wastewater generated during oil and gas activities (hydraulic fracturing and production) is commonly disposed of in deep formations, but the migration of this wastewater after entering the subsurface is poorly understood. This study uses numerical models to simulate wastewater disposal in the Paddy-Cadotte of Northeast British Columbia using both single-well axisymmetric box models and a regional model of the formation in which multiple disposal and water source wells operate. A sensitivity analysis performed on the box models reveals that dispersivity and permeability exert the strongest control on overall wastewater distribution. Models show that wastewater migrates further than predicted using a simple volumetric calculation, and extends further along the base of the formation than the top due to variations in fluid density. Interference between disposal and source wells is observed to influence wastewater migration, while formation dip and regional groundwater flow have no discernible impact.

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

Investigating regional groundwater flow influences on slope stability in unlithified materials

Author: 
Date created: 
2018-04-17
Abstract: 

Elevated pore pressures play an integral part in slope failure; however, the nature of the regional groundwater flow regime is often not incorporated in slope stability analysis. This research aims to improve our understanding of how the dynamic nature of the groundwater flow regime exerts control on the regional occurrence of landslides in unlithified materials. An integrated hydrogeological – geotechnical methodology is used to investigate the hydrogeological controls on slope stability in Northeast British Columbia. A two-part approach utilized both a series of steady-state groundwater models developed using SVFLUX to investigate the role of geologic contact geometry and hydrogeological characteristics, and a transient groundwater model developed using MIKE SHE to investigate the role of climate. The analysis of these groundwater results highlights implications of regional and local scale hydrogeological processes on pore water pressures. Several challenges were encountered in regard to investigating processes at fine scale resolution within in a large scale groundwater flow model, and an inability to export unsaturated zone results from MIKE SHE limited the slope stability modeling in SV SLOPE.

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

Investigating the geochemistry of selenium in the residual from biologically treated mine-impacted water

Date created: 
2018-04-16
Abstract: 

Bacterially-mediated wastewater treatment is commonly used to prevent selenium (Se) release to the environment. This research focuses on the characterization of a selenium-rich residual, the by-product of industrial wastewater treatment. Solid-phase selenium speciation was investigated through sequential extraction procedures (SEP) and X-ray Absorption near Edge Spectroscopy (XANES). Selenium mobility and changes in Se speciation were tested through batch experiments under varying redox and pH conditions. The residual exhibits some heterogeneity, and is dominated by metal selenide species, with some evidence for less-reduced Se species. The greatest Se mobility was in mildly oxidizing conditions at neutral pH which also showed the least speciation change in the residual. Under highly-oxidizing and/or low-pH conditions Se mobilization was lower and reaction was dominated by oxidation of the metal-selenides to Se0 and/or SeS2. Additionally, unexpected speciation changes in the solid phase during the SEP were observed.

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

Structural and mineralogical controls of gold mineralization at the Tajitos project, Sonora, Mexico

Date created: 
2018-04-03
Abstract: 

Tajitos is an orogenic vein-hosted gold deposit in Sonora, Mexico. The local geology is composed of Jura-Cretaceous volcanic and sedimentary strata, with syn-volcanic granodioritic plugs and a post-depositional gabbroic stock. North-northeast directed compression during the Laramide orogeny formed a fold and thrust belt, folding and faulting the local strata. During the late Laramide orogeny, a mineralization event occurred, forming syn-deformational vein-hosted gold, under brittle-ductile conditions in the mid- to upper crust. Post-mineralization Basin and Range extension accompanied the emplacement of lamprophyric dykes and reactivation of mineralized faults with normal movement. Gold mineralization is hosted in steeply dipping, southeast trending fault-fill veins with surrounding coeval zones of extensional veins and quartz-sericite-pyrite alteration. High-grade mineralization shoots within the veins plunge steeply west and moderately to the southeast. Gold in the fault-fill veins primarily occurs along crack-seal laminations associated with galena and chalcopyrite occupying interstities between quartz and rimming pyrite, arsenopyrite, and sphalerite.

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

Late Cenozoic glaciations and environments in southernmost Patagonia

Date created: 
2018-04-05
Abstract: 

This thesis advances understanding of late Cenozoic landscape evolution and glaciation in southernmost South America using continental sedimentary deposits and landforms in the Lago Cardiel region in the foothills of the southern Patagonian Andes and along the Atlantic north and south of the Strait of Magellan. The evolution of the landscape in these two areas was determined through landform mapping and relative chronologic landform correlations. Paleomagnetic characteristics of late Cenozoic sediments and basalt flows and the stratigraphy and sedimentology of Pleistocene glacial sediments in sea cliffs and anthropogenic exposures provide a chronology and evidence of depositional environments during Pleistocene glaciations. The landscape in the Lago Cardiel area changed significantly following the last major period of tectonic uplift at the end of the Miocene. Large west-trending valleys that incise Miocene-aged basalt were abandoned by their formative rivers about 4.4 Ma. The closed basin that contains Lago Cardiel began to form on the relict plain surface before 4.0 Ma and grew in size throughout the Pliocene and Pleistocene by a combination of erosion by small streams, deflation, colluviation, and possibly tectonic collapse. Drainage reorganizations occurred at about 4.0 Ma and 3.6 Ma, most likely initiated by increased aggradation or isostasy during Pliocene glaciations. Eolian, fluvial, and mass-movement processes continued to alter the landscape throughout the Pleistocene with higher rates during glacial periods. Evidence of at least three glaciations is recorded in the stratigraphic exposures at the Atlantic Coast and the shores of the Strait of Magellan. At Cabo Vírgenes and Bahía Posesión, two glacial drift units were deposited in a grounding-line environment. These sediments are normally magnetized and date to the Brunhes Chron (<0.78 Ma). The Tres de Enero highway cut exposes three subglacial tills deposited during the Great Patagonian Glaciation (GPG) – two normally magnetized tills that I assign to the early Brunhes Chron and a lower reversely magnetized till deposited during the Matuyama Chron (2.581-0.78 Ma). The reversely magnetized till and other reversely magnetized GPG sediments indicate that the earliest Pleistocene glaciations occurred before 0.78 Ma. In the Río Gallegos Valley, a 0.86 Ma basalt flow caps a thick unit of normally magnetized glaciofluvial gravel, which was probably deposited during the Jaramillo Subchron (1.075-0.991 Ma). This thesis provides a timeline for the evolution of the landscape of the Lago Cardiel region from the Miocene to the present. It also contributes to our understanding of the age and depositional environments of GPG and post-GPG 1 glacial events in the Strait of Magellan region by documenting the magnetic polarity of glacial sediments throughout the region.

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

GIS-based analysis of spring occurrence and spring source areas in Peace River Regional District, British Columbia

Author: 
Date created: 
2018-04-12
Abstract: 

Springs in the Peace River Regional District are important fresh water sources for domestic and industrial use, however, little is known about their hydrogeology. This study investigated the controls on spring occurrence and delineated the spring source areas (SSA). Samples from 36 springs were collected and analyzed for chemical and isotopic composition. The chemistry suggested 20 Quaternary and 16 Bedrock aquifer sourced springs. A GIS-based multi-criteria decision analysis integrated spring-related factors (slope, curvature, hydrogeological features, topographic wetness index, surficial geology, and drift thickness) to produce maps showing the likelihood for occurrence of Quaternary or Bedrock-sourced springs. There was a ~70% success rate for correctly identifying sources of the sampled springs. A GIS-based tool was applied to determine topographic SSA’s for 33 springs with varying degrees of success. Although both the maps and SSAs contain uncertainty, there is sufficient information to support decision-making in water resource protection and management.

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

Investigating the role of buried valley aquifer systems in the regional hydrogeology of the Central Peace Region in Northeast British Columbia

Date created: 
2018-01-31
Abstract: 

Geological and numerical flow models were developed to explore the hydraulic role of buried valley aquifers in regional groundwater flow and assess the potential groundwater resource. The study area was the central Peace Region in Northeast British Columbia. The reservoir software Petrel was used to construct the geological model of a buried valley network by integrating interpretations from an airborne electromagnetic survey (SkyTEM) and borehole gamma-ray and lithology logs. This detailed geological model and a simplified geological model were used to develop two numerical flow models in MODFLOW. The modelling results suggest that permeable deposits exist within the buried valleys, but are not regionally connected throughout the whole network, and thus do not play a significant role in the regional groundwater flow regime. However, extensive permeable deposits within the buried valleys appear to exist at smaller scales, and may offer a viable water source in the area.

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

Seismic and potential field constraints on the shallow crustal structure of inner Bering shelf, offshore southwestern Alaska

Author: 
Date created: 
2017-12-08
Abstract: 

South-western Alaska comprises a collection of major fault bounded tectonostratigraphic terranes that were accreted during Mesozoic and early Tertiary time. To characterize the offshore extension of these terranes and the various major faults identified onshore, I have reprocessed three intersecting multichannel deep seismic reflection profiles totalling ~750 line-km that were shot by the R/V Ewing across part of the inner Bering continental shelf in 1994. Since the uppermost seismic section is often contaminated by high amplitude water layer multiples from the hard and shallow seafloor, I have supplemented the migrated reflection images with high-resolution P wave velocity models derived by both traveltime tomography and waveform tomography of the recorded first-arrivals to depths of 2000 m. In addition, I have also incorporated other geophysical datasets such as: well logs, ship-board gravity, ship-board magnetics, satellite-altimetry gravity and air-borne magnetics to produce an integrated interpretation. The results delineate the offshore extension of the major geological elements onshore including: the Togiak-Tikchik fault, East Kulukak fault, Chilchitna fault, Lake Clarke fault, Togiak terrane, Goodnews terrane, Peninsular terrane, Northern and Southern Kahiltna flysch deposits, and the Regional Suture Zone.This thesis also focuses on mitigation of guided wave contamination in the application of 2-D acoustic waveform tomography to two small sections of a seismic line across the shelf: one section with deep igneous basement overlain by a thick pile of sediments and the other section with shallow basement and a thin sedimentary cover. I discuss the appearance of dispersive guided waves in both datasets, and show that with appropriate data preconditioning, suitable forward modelling parameters and careful choice of objective function, it is possible to invert the data using 2-D acoustic waveform tomography. I highlight use of the gradient image as a quality control tool at each iteration of the inversion process to assess the corresponding model updates. This thesis also discusses the practical limitations of waveform tomography applied to seismic data contaminated with strong dispersive guided waves, and concludes that traveltime tomography is sufficient in cases where the objective is to image relatively large low-velocity anomalies.

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

Late Cretaceous to Paleocene evolution of the Blanchard River assemblage, southwest Yukon; implications for Mesozoic accretionary processes in the northwestern Cordillera

Author: 
Date created: 
2017-11-02
Abstract: 

Bedrock mapping, petrography and U-Pb in-situ monazite and detrital zircon geochronology elucidates the geological evolution of the Blanchard River assemblage, southwest Yukon. The Blanchard River assemblage belongs to a series of Middle Jurassic to early-Late Cretaceous pull-apart basinal assemblages deposited between the Insular and Intermontane terranes. Detrital zircon maximum depositional ages from 130-120 Ma suggest Early Cretaceous deposition of the Blanchard River assemblage along the western Laurentian margin, detritus was sourced primarily from inboard Intermontane terranes with minor input from outboard Insular terranes. Collapse of the Blanchard River basin is recorded by 83-76 Ma deformation and associated amphibolite-facies metamorphism, interpreted as the timing of terminal Insular terrane accretion to the western Laurentian margin. A second phase of Blanchard River assemblage metamorphism indicates ca. 70 Ma retrograde metamorphism associated with exhumation. Intrusion of the Ruby Range suite induced contact metamorphism within the Blanchard River assemblage from 63-61 Ma.

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

The role of intact rock fracture in rockfall initiation

Date created: 
2017-10-11
Abstract: 

High, near-vertical rock faces were investigated to determine the role of intact rock fracturing in rockfall initiation. Terrestrial LiDAR and photogrammetry were used to characterize historical and recent rockfall failure surfaces at two sites – one natural cliff face, and one engineered mine wall. Intact rock fracturing associated with each rockfall was estimated by comparing failure surface geometry to mapped discontinuity orientation and persistence; and by the application of two point cloud roughness analysis techniques. Estimates of intact rock bridge proportion provided the constraints for input parameters of slope-scale distinct element models. These models used a time-dependent strength degradation code, applied to a Voronoi network, to reproduce observed failure mechanisms. These analyses also provided the basis for proposed LiDAR monitoring at each site, and a system for classifying and prioritizing areas of high rockfall initiation hazard. Results of this research allow for better understanding of the interaction between intact rock bridges and discontinuities in high vertical slopes.

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