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

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Late Cenozoic geology of La Paz, Bolivia, and its relation to landslide activity

Date created: 
2016-04-20
Abstract: 

La Paz lies in a deeply incised valley on the Bolivian Altiplano. It has experienced frequent damaging historic landslides and numerous, much larger, prehistoric landslides. I documented the Neogene and Pleistocene lithostratigrahic and magnetostratigraphic framework of La Paz, produced an inventory of recent (1995-2014) landslides, and characterized ongoing (2008-2011) slow ground motion using radar interferometry (InSAR). The upper part of the sediment sequence beneath the Altiplano is glacial in origin and fines distally away from the Cordillera Real. It records at least 15 late Pliocene and Early Pleistocene glaciations, most of which predate the oldest known North American continental glaciation. The plateau surface formed by ca. 1.0 Ma, but most likely before ca. 1.8 Ma. After that the headwaters of the Amazon River extending westward through the Cordillera Real incised the underlying sediments. The poorly lithified fill sequence is exposed in steep slopes, promoting instability. Between 1995 and 2014, La Paz experienced 43 discrete landslides and slow ongoing landslides at 13 additional locations. Landslides were most frequent late in the rainy season and generally happened after particularly wet periods weeks in length, indicating a strong hydro-meteorological control. The margins of several landslides coincide with buried culverted streams, indicating that this engineering practice reduced slope stability. InSAR results show that about one-third of slopes in La Paz are moving at rates up to ~20 cm/a. They also identify previously unknown landslides, detect hectare-scale movements of as little as ~0.5 cm/a, and indicate several distinct failure mechanisms. Many recent landslides correspond with large, creeping paleolandslide deposits, indicating that the reduced residual strength and modern activity of these deposits influences the localization of recent failures. My findings highlight aspects of slope instability in La Paz that can be used to reduce risk. Future failures are most likely to happen in previously displaced fine-grained sediments, particularly the slowly moving paleolandslides south and east of the city centre. Several key areas require detailed ground-based monitoring, particularly during the rainy season when cumulative precipitation thresholds are exceeded. The practice of burying river channels should be re-assessed, and a survey of existing culverted channels conducted.

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

Late Wisconsinan paleosols and macrofossils in Chehalis Valley: paleoenvironmental reconstruction and regional significance

Date created: 
2016-03-30
Abstract: 

A subalpine coniferous forest occupied the Chehalis Valley before 19,980 ± 70 years BP (UCIAMS 126600), according to plant and insect macrofossils and paleosol evidence preserved in Late Pleistocene-aged sediments. The paleoclimate was similar to the modern Engelmann spruce-subalpine fir (ESSF) ecosystem that occurs at high elevation with cold and wet climates today. The Chehalis Valley evidence challenges the interpretation that the Coquitlam Stade and the Port Moody Interstade were regional and driven by climate change. Coquitlam till is absent from Chehalis and there was a coniferous forest present when other areas in southwest British Columbia were covered by Coquitlam Stade ice.

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

Aquifer – stream connectivity at various scales: Application of sediment – water interface temperature and vulnerability assessments of groundwater dependent streams

Date created: 
2016-02-25
Abstract: 

Streams with greater connectivity to an aquifer are potentially more sensitive to changes in groundwater levels and fluxes than streams with less connectivity. Aquifer-stream connectivity during the summer low flow period is of particular concern because this is a period of maximum relative groundwater contribution to stream flow volumes, which coincides with periods of peak water demands and critical aquatic habitat needs. Field and statistical methods were used to characterize aquifer - stream connectivity and evaluate factors influencing the groundwater flux to streams at different scales during the summer low flow period. The research focused on the use of sediment-water interface temperature in combination with a range of field methods, including manual stream discharge measurements, seepage meters, and in-stream piezometers, to characterize aquifer - stream connectivity in Fishtrap and Bertrand Creeks in the Lower Fraser Valley of southwest British Columbia. A combination of field measurements aided in reducing measurement uncertainties and improved estimation of the groundwater flux. A simplified heat budget demonstrated that, despite their similar climate and geographical setting, the groundwater flux during the summer periods was higher in Fishtrap Creek than in Bertrand Creek, due to its more permeable geological substrate. Independent component analysis (ICA) combined with cross-correlation was a novel approach to temperature signal separation. ICA directly linked the extracted signals to factors in the heat budget that influence sediment-water interface temperatures within a stream reach. Surface heating from solar radiation was the dominant factor influencing the interface temperature in most years, but there is evidence that thermal exchanges took place at the water-sediment interface, and the correlation with groundwater levels indicated these heat exchanges were associated with groundwater influx. Overall, the combined approaches were able to attribute temporal and spatial variability in streamflow and sediment-water interface temperatures to relative contributions of groundwater to streams.The understanding of aquifer-stream connectivity at different scales was applied in the development of a vulnerability framework for assessing stream vulnerability to changes in groundwater conditions. This framework can be used in support of decision making surrounding Sensitive Stream Designation in British Columbia and water allocation under the Water Sustainability Act.

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

LiDAR and geomorphic characterisation of landslide-induced liquefaction deposits in the eastern Swiss Alps

Date created: 
2015-12-08
Abstract: 

The Flims rockslide, located in the eastern Swiss Alps, is the largest postglacial landslide in Europe. About 9400 years ago, 10-12 km3 of limestone detached from the north wall of the Vorderrhein River valley and rapidly fragmented, impacting and liquefying approximately 1 km3 valley-fill sediments. A slurry of liquefied sediment, the “Bonaduz gravel”, traveled 16 km downvalley and up the Hinterrhein valley, carrying huge fragments of rockslide debris (tumas). The sheet of liquefied sediments is >60 m thick and fines upward from cobble gravel at the base to sand at the top. Another large, slightly older rockslide (Tamins rockslide) blocked the Vorderrhein River and impounded a lake into which the Flims rockslide fell, increasing the mobility of the Bonaduz flow and affecting its flow path. I used field observations and a LiDAR-based DEM to map the Bonaduz gravel and infer its mechanism of emplacement.

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

Modern and ancient perspectives on deposition across the tidal–fluvial transition in rivers

Date created: 
2015-11-30
Abstract: 

The tidal–fluvial transition (TFT) in rivers exhibits a complex distribution of sediments and bioturbation that results from the interaction between river flow and tides. In the Fraser River, British Columbia, Canada, inclined heterolithic stratification (IHS) accumulates in intertidal positions on channel bars across the longitudinal profile of the TFT. Correspondingly, this portion of the river is studied to gain insight as to how sediments are distributed. The Cretaceous-aged McMurray Formation of Alberta, Canada contains thick and widespread IHS successions in the southern Athabasca region that accumulated on channel bars in a large river. This thesis focuses on identifying physical manifestations of channel-bar deposits that reflect along-strike variations in depositional processes within the TFT. These observations are put forward as criteria that can be used to determine depositional position relative to the TFT for other river systems in the modern and rock record. Vibracores, box cores, and surface-sediment samples were collected from nine channel-bars across the Fraser River’s TFT. Results show that mud bed thickness and mud volume are highest in the freshwater to brackish-water transition zone, with bioturbation decreasing from seaward to landward across the TFT. Heterolithic bedding is formed where mud is deposited, and is limited to locations with persistent brackish-water conditions. In the freshwater and tidal realm, amalgamated sand beds dominate channel-bar successions, although sand-mud rhythmicity increases towards the river mouth and reflects seasonal variations in river discharge. Thirty-one subsurface cores of the McMurray Formation were analyzed to test the depositional trends defined from the TFT in the Fraser River. Quantification of sedimentological and ichnological parameters was undertaken to differentiate between channel-bar successions deposited towards the seaward, middle, and landward ends of the paleo-TFT. The core dataset utilized in this study is too limited to draw direct comparisons between the Fraser and the McMurray, yet, trends are identified that suggest a potentially broad TFT was present in the “A Valley” of the McMurray Formation in the southern Athabasca region. Further work is needed to confirm this assessment.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Shahin Dashtgard
James MacEachern
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.

Predicting the geochemical effects of SO2 impurities during carbon storage: Batch experiments and reaction path geochemical modelling

Author: 
Date created: 
2015-12-01
Abstract: 

The objective of this study was to improve our ability to predict CO2-SO2 geologic storage. SO2 is an impurity of industrial CO2 gas streams which is expected to intensify brine acidification resulting in enhanced mineral reaction. Short-term H2SO4-brine-rock experiments were combined with reaction path modelling to identify reactions and evaluate the pH and temperature dependency of reaction rates. In addition, available reactive surface area was investigated to enhance our ability to upscale to reservoir scale. Kinetically controlled reaction path models that included CO2, SO2 and O2 were generated and then run at reservoir conditions for 100 y. The models predicted a rapid buffering of the SO2 induced acidification. Compared to pure CO2 storage the CO2-SO2-O2 reservoir models resulted in enhanced carbonate reaction extents and a greater porosity increase, which have significant ramifications for the safety of the seal and the storage capacity of the storage formation.

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

Assessing the Risk of Saltwater Intrusion on the Gulf Islands, BC

Date created: 
2015-09-30
Abstract: 

In coastal regions, the quality of groundwater can be compromised due to saltwater intrusion (SWI) caused by various natural (sea level rise and storm surge) and anthropogenic (pumping) hazards. The goal of this research was to distinguish groundwaters impacted by SWI in the bedrock aquifers of the Gulf Islands, BC and identify thresholds for select chemical parameters that can be used for monitoring purposes, as well as to develop and test an approach for assessing risk to groundwater quality in coastal aquifers. The most reliable indicators were Cl/(HCO3 + CO3), BEX (base exchange index), Cl vs. EC, depth vs TDS, and a quantile analysis, resulting in 138 well samples (out of 795) that appear to be impacted by SWI. Based the 95th percentiles, for which 100% of the samples graphically showed strong evidence of SWI, the recommended threshold for Cl is 480 mg/L, 2,090 µS/cm for EC, and 970 mg/L for TDS. These samples were collected from wells that predominantly fall along the coastline. The vulnerability of the bedrock aquifers to SWI was assessed spatially by mapping hazards in combination with the aquifer susceptibility. Hazards due to pumping have the greatest influence on the vulnerability. Risk was evaluated spatially using an economic valuation of loss – here replacement of a water supply. The combination of chemical indicators and risk assessment maps are useful tools for identifying areas vulnerable to SWI, and these tools can be used to improve decision-making related to monitoring and community development for coastal areas.

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

Characterization of Brittle Damage in Rock from the Micro to Macro Scale

Author: 
Date created: 
2015-08-10
Abstract: 

An Increasing need for mining and constructing underground facilities at a greater depth and under high in-situ stresses have introduced new challenges in the form of brittle rock fracture. Brittle fracture is a complex mechanism comprising different stages of failure including initiation, propagation and coalescence. Brittle fracture studies in rock can be undertaken at a wide range of scales from the micro scale i.e. microcrack/grain scale in laboratory samples through the meso scale (underground excavations) to the macro scale such as in-situ engineered/natural rock slopes or block cave mines. At all these scales the rock/rock mass is subjected to “damage” which influences the engineering performance. Improved understanding of brittle damage at various scales requires development of damage intensity measures to quantify brittle fracture for both pre-existing and stress-induced fractures and the use of advanced numerical modelling approach. In this study, a state-of-the-art numerical modelling approach based on the combined finite/discrete element method (FDEM) is integrated with discrete fracture network engineering, DFNE, in order to evaluate brittle damage at varied scales. The influence of micro-heterogeneity is studied at the laboratory scale by incorporating a micro discrete fracture network (µDFN). A wide range of laboratory testing including Brazilian, uniaxial, biaxial and triaxial compression tests are modeled to investigated the complete 3D fracture process. At the meso scale, mechanisms leading to strain bursting and spalling damage around underground openings are studied focusing on the influence of pre-existing cracks in a massive rock mass. Finally at the macro scale, a finite/discrete element modelling approach coupled with a discrete fracture network (FDEM-DFN) is utilized to analyze the hanging wall surface subsidence associated with sub-level caving. A suite of model data interpretation methods including time-displacement hanging wall deformation characterization, numerical inverse velocity analysis and virtual hanging wall inclinometers is adopted to improve our understanding of the extent and mechanism of hanging wall failure with mine advance.

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

Characterization and Analysis of the Mitchell Creek Landslide: A Large-scale Rock Slope Instability in northwestern British Columbia

Date created: 
2014-08-13
Abstract: 

The Mitchell Creek Landslide (MCL) is a large, 74 Mm3, complex, active landslide located in the Coast Mountains of B.C. The slope is composed of foliated and hydrothermally altered volcanic-sedimentary rocks. The Mitchell Thrust and Brucejack faults constrain landslide geometry. Visible deformation initiated mid-20th century, coincident with rapid glacial retreat. This thesis presents results of a detailed characterization study which combines the results of geomorphological analysis, deformation feature mapping, and photogrammetric analysis of historic aerial photography from 1956, 1972, 1992, and 2010; geological and geomechanical borehole data; and geotechnical monitoring of landslide motion and groundwater conditions. Rates of movement vary spatially by geomorphological zone between 0.80 m/yr in the toe to 0.19 m/yr at the backscarp. Numerical modelling simulations were undertaken using continuum and discontinuum methods to evaluate failure mechanisms and landslide evolution. Glacier retreat, regional geology and rupture surface configuration were identified as the primary controls on landslide behaviour.

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

Geostatistical modeling and upscaling permeability for reservoir scale modeling in bioturbated, heterogeneous tight reservoir rock: Viking Fm, Provost Field, Alberta

Author: 
Date created: 
2015-08-13
Abstract: 

While burrow-affected permeability must be considered for characterizing reservoir flow, the marked variability generated at the bed/bedset scale makes bioturbated media difficult to model. Study of 28 cored wells of the Lower Cretaceous Viking Formation in the Provost Field, Alberta, Canada integrated sedimentologic and ichnologic features to define recurring hydrofacies possessing distinct permeability grades. Transition probability analysis was employed to model spatial variations in biogenically enhanced permeability at the bed/bedset scale. Results suggest that variations in permeability are strongly related to variations in hydrofacies rather than grain size. The variability in permeability at the bed/bedset scale was simplified by calculating an equivalent permeability that represents the thickness-weighted sum of permeability at the bed/bedset scale using expressions for layered media. Numerical block models were then generated for both the bed/bedset hydrofacies and the upscaled hydrofacies. Vertical and horizontal flows were simulated at both scales, and the volumetric flows in each direction were compared to verify the representativeness of the equivalent permeability. Vertical and horizontal flows simulated for bed/bedset scale and composite hydrofacies differ by less than +/-5%, suggesting that permeabilities at the bed/bedset scale can be simplified through upscaling. Reservoir-scale groundwater flow was simulated along a hydrogeological cross section comprised of the composite hydrofacies. The resulting flow regime was consistent with those simulated using permeability estimates from tight reservoir units of the Viking Formation. This approach may lead to improved reserve calculations, estimates of resource deliverability, and understanding of reservoir responses during recovery.

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