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

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Three dimensional strain distribution and deformation temperature interpreted from quartz microstructures and petrofabrics in the Okanagan Valley shear zone, southern Canadian Cordillera

Date created: 
2014-07-18
Abstract: 

The Eocene Okanagan Valley shear zone (OVsz) is a ~1-1.5 km thick, <30° west-dipping, extensional ductile to brittle detachment that facilitated exhumation of the southwestern Shuswap metamorphic complex in the southern Canadian Cordillera. A predominantly top-to-the-WNW sense of shear is confirmed by meso- and micro-shear-sense indicators. Quartz a-axis patterns obtained from crystallographic preferred analysis suggest general plane strain conditions with some constriction in the upper 150m of the shear zone. Deformation temperatures derived from recrystallization mechanisms and crystallographic orientations of quartz progressively increase from ~280 to >650 ° down the exposed structural section. The observed telescoping of isotherms in the immediate footwall of the OVsz is interpreted to be the result of detachment-parallel penetrative general shear flow in predominantly plane strain deformation during progressive exhumation. This thesis discusses the possible processes that could have been responsible for this intense compression of isotherms in the immediate footwall of the OVsz.

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

The Hydrogeology of Salt Spring Island, British Columbia

Date created: 
2014-08-06
Abstract: 

Groundwater on Salt Spring Island, British Columbia, flows through fractures in sedimentary and igneous rock aquifers. Recharge is dominantly by rainfall infiltration. At a local scale, groundwater discharges into lakes and streams; regional flow is toward the coast where the groundwater discharges to the ocean. Groundwater evolves from a Na-Cl rainwater to a Ca-HCO3 type through calcite dissolution. Cation exchange (Ca exchanges for Na) is a dominant process in the sedimentary rocks (but not in the igneous rocks), resulting in a Na-HCO3 type water. Mixing with a Cl-rich end-member is also a dominant process in both rock types. Some wells near the coast are known to be impacted by saltwater intrusion. Despite the differences in scale for testing, and rock type, pumping and tidal response tests yield similar averages across the Gulf Islands. Transmissivity is estimated on the order of 10-5 to 10-4 m2/s and hydraulic conductivity on the order of 10-7 to 10-6 m/s. Using Visual MODFLOW, a steady-state fresh groundwater simulation for the Swan Point area generated a representative flow system and established a reasonable range for the aquifer properties. A tidally-forced transient model simulated the tidal response and further constrained the aquifer properties. Next, a density-dependent flow and transport model was constructed in SEAWAT to simulate the current position of the saltwater interface, which was found to be near vertical at the coast. The lack of a wedge likely reflects the relatively steep topography at this site and suggests that submarine groundwater discharge may occur. However, the small model domain and imposed boundary conditions may over-estimate the amount of inflowing water. The SEAWAT model was then used to determine the sensitivity of the aquifer to climate change, encompassing an increase in mean annual recharge by ~1.5 % and SLR of 1.17 m by the end of this century, as well as pumping. Model results showed no significant impacts to the salinity distribution or saltwater wedge geometry at this particular site due to the steep topography. Areas with less steep topography may have greater impacts and merit further research.

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

Characterisation of large catastrophic landslides using an integrated field, remote sensing and numerical modelling approach

Date created: 
2014-04-09
Abstract: 

I apply a forensic, multidisciplinary approach that integrates engineering geology field investigations, engineering geomorphology mapping, long-range terrestrial photogrammetry, and a numerical modelling toolbox to two large rock slope failures to study their causes, initiation, kinematics, and dynamics. I demonstrate the significance of endogenic and exogenic processes, both separately and in concert, in contributing to landscape evolution and conditioning slopes for failure, and use geomorphological and geological observations to validate numerical models. The 1963 Vajont Slide in northeast Italy involved a 270-million-m3 carbonate-dominated mass that slid into the newly created Vajont Reservoir, displacing water that overtopped the Vajont Dam and killed 1910 people. Based on literature, maps and imagery, I propose that the landslide was the last phase of slow, deep-seated slope deformation that began after the valley was deglaciated in the Pleistocene. Field and air photograph observations and stream profiles provide the context of Vajont Slide. The first long-range terrestrial digital photogrammetry models of the landslide aid in characterising the failure scar. Analysis of the failure scar emphasises the complexity of the failure surface due to faults and interference between two tectonic fold generations, influencing failure behaviour. Observations of the pre- and post-failure slope and interpretation of numerical simulations suggest a complex three-dimensional active-passive wedge- sliding mechanism, with two main landslide blocks and five sub-blocks in the west block, separated by secondary shear surfaces. The 1959 Madison Canyon Slide in Montana, USA, was triggered by an M = 7.5 earthquake. A 20-million-m3 rock mass descended from the ridge crest, killing 24 people and blocking Madison River to create Earthquake Lake. Marble at the toe of the slope acted as a buttress for weaker schist and gneiss upslope until the earthquake undermined its integrity and triggered failure. Rock mass characterisation, long-range terrestrial digital photogrammetry, and kinematic analysis indicate that the lateral, rear, and basal release surfaces formed a hexahedral wedge-biplanar failure. Dynamic numerical modelling suggests topographic and damage amplification due to ridge geometry and pre-existing tension cracks. Analysis of the case studies highlights the complexity of large, catastrophic rock slope failures, their causes, and their evolution from incipient failure to disaster.

Document type: 
Thesis
Senior supervisor: 
Doug Stead
John J. Clague
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.

Modelling hard rock pillars using a Synthetic Rock Mass approach

Author: 
Date created: 
2014-03-20
Abstract: 

Rock pillar strength and the characterisation of pillar failure mechanisms are of major importance in mine design. The recently developed Synthetic Rock Mass (SRM) approach provides a state-of-the-art numerical technique to more accurately characterize the mechanical properties of rock pillars. The SRM approach used in this thesis is based on a combination of two well accepted numerical methods, a Particle Flow Code (PFC3D) incorporating a Discrete Fracture Network (DFN). This research presents the results of a systematic study of the use of SRM modelling for hard rock pillars. The effect of assumed joint set characteristics (orientation and persistence) is first investigated through comparison of the numerical results from a series of conceptual pillar models. The joint set properties are shown to have important controls on the pillar peak strength, deformation modulus, lateral stiffness and the pillar strain-softening gradient in the post-peak stage. The effect of pillar confinement is then examined using two conceptual pillar models with varied slenderness (Width/Height ratio). The pillar confinement effect is investigated by comparing the axial and lateral stresses at the pillar core and pillar boundaries, and this effect attributed to the lateral restraint due to the loading platens. The confinement effect is further examined using a series of triaxial compression test simulations in which the pillar peak strength, residual strength and post-peak strain-softening gradient are quantified. Simulations of the development of 3D cracks in two jointed pillar models, including wing cracks, large scale crack coalescence and step path failure are presented. A 3D visualisation of internal pillar failure mechanisms is illustrated by examining crack development and the changes in the localised stresses within the pillar model. Research presented will contribute significantly to the development of a more robust SRM approach for rock pillar design.

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

Diachronous deformation, metamorphism and exhumation in the northern Canadian Cordillera: revealed from pressure-temperature-time deformation paths of former mid-crustal rocks

Date created: 
2014-03-26
Abstract: 

The lowest structural and stratigraphic levels of the Yukon-Tanana terrane and the structurally underlying parautochthonous North American margin rocks were metamorphosed at similar conditions (7.5 – 9 kbar; 600 – 680 °C) and share a common style of deformation, characterized by the transposition of lithologic contacts and primary compositional layering into a regional ductile foliation (ST) with at least one generation of intrafolial isoclinal folds. Equilibrium assemblage modeling and in situ U-Th-Pb SHRIMP dating of monazite are used to place quantitative constraints on the conditions and timing of deformation, metamorphism and subsequent decompression. These data reveal that these fabrics, and the associated metamorphism, did not develop during a single tectono-metamorphic event. Rather, ductile deformation and high-grade metamorphism developed diachronously. Rocks deformed and metamorphosed in the Permo-Triassic and Early Jurassic were exhumed in the Early Jurassic, while rocks to the northeast in the Finlayson domain were buried, heated and ductiley deformed at mid-crustal levels (~25 km depth) from the Middle Jurassic to Early Cretaceous (c. 169 – 142 Ma). Metamorphism continued at an even deeper crustal level (~ 30 km depth, as recorded in the Australia Mountain domain), propagating downward into the parautochthonous North American crust in the Early Cretaceous (c. 146 – 118 Ma). Together, these data reveal a spatial and temporal pattern of structurally downward younging deformation and metamorphism that corresponds with the foreland-directed growth of a critically tapered orogenic wedge. In this model, rocks in front of the wedge are episodically underthrust downward into a distributed, high-grade transposition shear zone at 25 to 30 kilometres depth near the base of the overriding wedge. Rocks previously underthrust, buried and metamorphosed are progressively exhumed to higher structural levels within the wedge, as the upper crust enters a state of extension in order to maintain a critically tapered wedge. Rocks that occupied the mid-crustal shear zone in the Middle Jurassic and Early Cretaceous (Finlayson and Australia Mountain domains) were exhumed in the mid-Cretaceous along southeast-directed (orogen-parallel) extensional faults, from beneath a supracrustal ‘lid’ that had previously been metamorphosed and ductiley deformed at amphibolite facies in the Permo-Triassic and Early Jurassic.

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

Late Holocene history of Squamish River north of Brackendale, British Columbia

Date created: 
2014-03-14
Abstract: 

Laminated silt, organic-rich silt, and peat exposed in the banks of Squamish River north of Brackendale, British Columbia, provide evidence for a lake impounded behind Cheekye Fan during the late Holocene. The lake gradually filled with sediment as Squamish River advanced its delta and floodplain southward toward the fan. Radiocarbon ages on detrital and growth-position plant fossils provide evidence that the lake reached up to 9 km upstream of Cheekye Fan about 3400 years ago and persisted until about 2300 years ago. Geomorphic observations and the distribution of fine-grained facies indicate that both Cheakamus and Squamish rivers contributed sediment to the lake; consequently, different depositional environments existed near Cheekye Fan than farther upstream. Debris flows that travelled down Cheekye River to Cheakamus River provided fine-grained sediment that accumulated in the deepest part of the lake just north of the fan. Farther upstream, organic-rich silt was deposited in fens and marshes surrounding the lake. Squamish River is confined by steep banks of cobble-boulder gravel 1.5–2 km north of the present Cheakamus-Squamish confluence, suggesting that coarse sediment transported by Cheakamus River controlled the lake outlet and, accordingly, lake level. As sediment delivery from Cheakamus and Cheekye rivers declined through the late Holocene, the lake outlet was progressively lowered and the lake drained. Sedimentation in Squamish Valley upstream of Cheekye Fan is also influenced by landslides at Mt. Cayley, 45 km upstream. A large landslide at Mt. Cayley about 1100 years ago produced a sediment pulse that propagated downstream and caused the floodplain above Cheekye Fan to aggrade. Sand buried the remaining fens that covered part of the low-gradient floodplain, leading to their replacement by coniferous and riparian forest. The model that I use to interpret Squamish River sedimentary environments can be applied to other low-gradient floodplains influenced by alluvial fans.

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

Paleoenvironmental interpretation and depositional process classification of allomembers D and E, lower Horseshoe Canyon Formation, Alberta, Canada

Date created: 
2014-03-04
Abstract: 

Outcrops of allomembers D and E of the Late Cretaceous, Horseshoe Canyon Formation comprise marginal-marine units deposited on the western margin of the Western Interior Seaway. Associated facies are grouped into seven element complexes (EC; equivalent to facies associations) and 3 larger-scale element complex assemblages (ECA; equivalent to a depositional setting). Allomember D is classified as a tide-dominated, fluvial-influenced (Tf) ECA, and comprises two element complexes: Tf-tidal flat EC and F-onshore EC. Allomember E1 forms a tide-dominated, fluvial-influenced, wave-affected (Tfw) ECA that is composed of four ECs: Twf-tidal flat, Ft-channelized-A, Ft-channelized-B and F-onshore ECs. Allomember E2 forms a wave-dominated, tide-influenced, fluvial-affected (Wtf) ECA that consists of four ECs: Wtf-lobe, Wft-mouthbar, Tf-tidal flat EC and F-onshore ECs. Through classification of the element complexes within the allomembers, lateral and vertical changes in hydraulic processes are recorded and analyzed, highlighting the depositional variability within single parasequences and between parasequence sets in marginal-marine environments.

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

The northern Cache Creek terrane: record of Middle Triassic arc activity and Jurassic-Cretaceous terrane imbrication

Author: 
Date created: 
2014-01-24
Abstract: 

The northern termination of the Cache Creek terrane in the Cordillera contains oceanic crustal lithologies including subalkaline mafic intrusive rocks with an arc geochemical signature, mafic volcanics with arc to back-arc signatures, and an arc-flanking volcaniclastic succession informally termed the Michie formation. This formation contains unimodal zircon populations with U-Pb dates of 245.85 ± 0.07 and 244.64 ± 0.08 Ma. These dates differ from the dominant detrital zircon age population of ca. 190 Ma found in the adjacent Whitehorse trough, but are similar to igneous crystallization ages of the Kutcho arc of northern British Columbia. Two main faults record oppositely verging deformational events: 1) The Judas Mountain thrust, a west-verging structure that emplaced Cache Creek terrane rocks above Stikinia and the Whitehorse trough, and 2) the Mount Michie thrust, an east-verging second phase structure that imbricated Stikinia and Whitehorse trough rocks onto and replaced them over the Cache Creek terrane.

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

Multiphase flow and reactive transport modelling of CO2 storage in heterogeneous reservoirs

Date created: 
2013-12-06
Abstract: 

This study addresses how physical heterogeneity, representing different sedimentary rock layers and the relationships between those layers, impacts the distribution of CO2, and thus the type and extent of mineral dissolution and precipitation reactions during CO2 geologic storage in deep saline aquifers. Numerical multiphase flow (TOUGH2) and reactive transport codes (TOUGHREACT) were used to construct a series of reservoir scale simulations to investigate how the flow controlling parameter values, distribution, and grid refinement of various hydrostratigraphic units (HSUs) affect the distribution of CO2, pH and mineral reactions. Physical heterogeneity is critical for controlling the distribution of supercritical and dissolved CO2, the redistribution of ions from geochemically reactive materials to more stable portions of the reservoir, mixing and dilution of CO2-rich waters, and the extent of mineral dissolution and precipitation reactions. The highest magnitude of carbonate mineral precipitation occurs at the sandstone-siltstone interface and along the extent of the CO2-water contact.

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

Facies Modelling of a Tide-Influenced, River-Dominated Delta, Fraser River Delta, British Columbia, Canada

Author: 
Date created: 
2014-01-27
Abstract: 

The Fraser River delta is a tide-influenced, river-dominated delta that exhibits distinct asymmetry in sedimentological and neoichnological character between the updrift (south) and downdrift (north) sides of the delta front and upper prodelta (< 200 m water depth). The updrift portion consists mainly of sands and heterolithic sand and mud bedsets with low bioturbation intensities (BI 0-3). Trace suites are sporadically distributed and include elements of the Skolithos Ichnofacies. The downdrift portion is composed of homogeneous mud beds and bedsets with significantly higher intensity of bioturbation (BI 3-6). Trace suites are attributable to the Cruziana Ichnofacies. The asymmetrical distribution of sediment and burrows on the delta is primarily controlled by strong northward-directed tidal currents. Physical sedimentary processes differ significantly between updrift and downdrift sides of the delta. The updrift delta is mainly an area of erosion in which strong tidal currents scour previously deposited sediments. This scouring reveals underlying sandy paleo-distributary channel deposits. The downdrift delta, on the other hand, is an area of net sediment (predominantly mud) accumulation. Sandy material eroded from the updrift delta is trapped within a deep submarine channel and does not get redistributed to the downdrift delta. This results in contrasting substrate types between the updrift and downdrift delta. The asymmetrical character of the Fraser River delta is similar in its sedimentological signature, but ichnologically distinct, from the wave-dominated asymmetric delta model. Neoichnological trends are opposite to that observed in wave-dominated asymmetrical deltas, in that the trace diversity and density are higher on the downdrift side of the delta front than the updrift side. Based on the results presented herein, a new tidally asymmetric delta model is proposed which, overall, leads to a more robust asymmetric delta model. The most important aspect of this new model is that tidally-influenced asymmetric deltas are not depth-dependent, and therefore, they have greater potential to develop in deep water settings than wave-dominated asymmetric deltas.

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