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

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Age, formation and tectonism of the Neoproterozoic Ruddock Creek zinc-lead deposit and host Windermere Supergroup, northern Monashee Mountains, southern Canadian Cordillera

Author: 
Date created: 
2016-08-24
Abstract: 

The Ruddock Creek property is located in the northern Monashee Mountains, southern British Columbia. The deposit is hosted by Neoproterozoic metasedimentary rocks of the Mica Creek succession within the Windermere Supergroup. Structurally the Ruddock Creek property is interpreted to reside within the base of the Selkirk allochthon, in the immediate hanging wall of the Monashee décollement, a crustal-scale, northeast-directed thrust-sense shear zone. The Neoproterozoic strata have been complexly folded and transposed by Mesozoic deformation. U-Pb dates for deformational events range from ca. 116 to 63 Ma (63 Ma being the end of ductile deformation). The geometry of the main sulphide body indicates that the mineralized horizon was subject to all phases of deformation and was metamorphosed to amphibolite facies. Detrital zircon geochronology provides U-Pb ages that constrain the provenance for the host Windermere Supergroup, and define a maximum depositional age of ca. 663 Ma. The 663 Ma age is not common to the North American Cordillera, and is found almost exclusively in igneous rocks in central Idaho, suggesting south to north transportation of sediment along the Neoproterozoic rifted paleo-margin of western Laurentia. The 206Pb/204Pb isotope ages of galena, pyrite and pyrrhotite from several mineralized horizons that make up the Ruddock Creek deposit indicate an Early Cambrian, 535 ± 30 Ma model age of mineralization. Different colour sphalerites and calcite were analyzed to generate a Rb/Sr errorchron with an age of ore formation of 556 ± 420 Ma. Together the maximum age of deposition, the Pb isotope ages and the Rb/Sr errorchron reveal a spatial and temporal syngenetic relationship of the deposition of the Mica Creek succession within the Selkirk allochthon and the mineralized horizon at the Ruddock Creek property. Local basement topography, such as horst and graben structures resultant from rifting related to the final phase of breakup of Rodinia, may have focused fluid flow into carbonaceous host lithology at Ruddock Creek. Local structural and stratigraphic traps, hydrothermal fluids, as well as the redox state of the basinal brines, would ultimately have localized and controlled the precipitation of the sulphides.

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

Modeling Paleorecharge on the Yucatan Peninsula, Mexico

Date created: 
2016-08-15
Abstract: 

The decline of the Mayan Civilization is thought to be caused by a series of droughts that affected the Yucatan Peninsula during the Terminal Classic Period (TCP) 800-1000 AD. This study modeled groundwater recharge for the TCP and the historical period (1979-2005). Precipitation was reconstructed using proxy data for the Yucatan Peninsula. Drought periods were identified, but the annual time scale for the proxy data precluded their use for recharge modeling. A daily time series representative of the TCP climate was thus generated using a novel backward shift factor approach using output from the Community Climate System Model Version 4 (CCSM4). Shift factors (for precipitation and temperature) were applied to observed precipitation data for recharge modeling. Average annual recharge was 1.7% higher during the TCP, and the majority of this higher recharge occurred during the wet season. These changes indicate the Yucatan Peninsula may have been susceptible to dry season droughts.

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

Stratigraphy and architecture of shallow-marine strata on an active margin, lower Nanaimo Group, Vancouver Island, BC

Author: 
Date created: 
2016-08-10
Abstract: 

An outcrop-based study of the Late Cretaceous Lower Nanaimo Group in the Nanaimo Basin was conducted to assess depositional architectures in a forearc basin and refine its stratigraphic relationships. Unlike foreland basins and on passive margins, transgressive shoreline successions are commonly observed in the Nanaimo Basin and developed in response to tectonically induced base-level changes and high sedimentation rates. Through a comparison of my results to previously studied transgressive succession and process-response relationships, a conceptual model is developed for predicting transgressive shallow-marine shoreline architectures in sedimentary basins. From a stratigraphic perspective, analysis of key measured sections shows that lower Nanaimo Group strata represent four facies associations: FA1, FA2, FA3, and FA4. The existing lithostratigraphic framework does not consider these depositional architectures, and this work demonstrates that a sequence stratigraphic framework is needed for the lower Nanaimo Group.

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

Multidisciplinary investigation of the evolution of persistently active basaltic volcanoes

Abstract: 

The size, shape, location and/or chemical evolution of basaltic magma plumbing systems at most volcanoes is not well constrained. Having this information beneath active systems allows scientists to target areas which will likely be the first to display volcanic unrest. With these constraints and datasets that cover long periods of time or include anomalous topographic features, we can start to investigate how a volcanic system has changed over time. To accomplish this, geochemical and geophysical studies at Masaya volcano (Nicaragua) and Mauna Loa volcano (Hawaii, USA) were conducted. Melt Inclusions were collected from Masaya volcano to investigate the processes within the magma chamber. The almost unchanging chemistry of the whole rock, crystals and melt inclusions regardless of which eruptive cone sampled suggests that the system is buffered in both temperature and chemistry. A large deep reservoir with rapid transit times to the surface could explain the data. Bouguer gravity mapping data at Masaya and Mauna Loa volcanoes were collected, processed and inverted to constrain the location and volumes of density anomalies at depth. Beneath Masaya volcano, the gravity data provides evidence of a very large intrusive complex (< 900 km3) at 4-9 km depth as well as several small shallow anomalies perhaps due to ring dykes around a buried caldera rim. This study strengthens arguments that Masaya does not have a large shallow magmatic system and that shallow endogenous growth is minimal. Gravity mapping and inversions from Mauna Loa provide evidence for relatively rapid rift zone migration most likely caused by a large edifice destabilizing event. The massive Ālika debris flows are contemporaneous with the age of rift zone migration suggesting that mass wasting is the cause.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Glyn Williams-Jones
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Dissertation) Ph.D.

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.