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

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Paleolimnology of Kluane Lake

Date created: 
2007
Abstract: 

Causes and consequences of late Holocene fluctuations of Kluane Lake in Yukon Territory have been reconstructed from several sediment cores. In the last 5000 years the level of Kluane Lake has varied from ~27 m below its present level to 12 m above, primarily due to changes in inputs of water from Slims and Duke rivers. Discharge form the Slims River catchment into Kluane Lake is associated with glacial advances. During periods when neither Duke nor Slims rivers flowed into Kluane Lake, the level of the lake fell and stable thermal stratification developed with anoxic conditions in the hypolimnion. Climate related changes in catchment permafrost affected nutrient mineralization and the quality of runoff. Recent Kluane Lake fluctuations have caused corresponding shifts in the local groundwater table, which has affected adjacent small lakes causing an alternation of open and closed basin conditions and reversals in local groundwater flow.

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

Holocene glacier fluctuations in Garibaldi Provincial Park, southern coast mountains, British Columbia

Author: 
Date created: 
2006
Abstract: 

Glacier fluctuations of the last 10,000 years have been reconstructed in Garibaldi Provincial Park in the southern Coast Mountains, British Columbia, from historical documents, dendrochronologic and lichenometric dating of moraines, and radiocarbon dating of fossil wood in glacier forefields. Six major periods of glacier advance are recognized: 7700-7300,6400-5100,4300,4100-2900,1600-1100 14c years BP, and the last millennium. Evidence for each of these six periods was found in the forefield of Sphinx Glacier, the only glacier in western North America with so complete a record. Evidence for each period, except the 4300 14c years BP event, was found at two or more sites, showing the regional sigmficance of the advances. The data demonstrate that the Little Ice Age in Garibaldi Park began as early as AD 1000. The earliest maximum was achieved in the lYh century, followed by recession until sometime in the 14'~ century. Several glaciers advanced into forests in the 14'1~ century, culminating with the construction of moraines in the late early lath, lgth, and early 2oth centuries. Helm Glacier provides a near complete record of fluctuations since the 14'~ century. Glaciers receded between the 1930s and 1960s at average annual rates of about 30 m. Between the 1960s and 1980s, glaciers advanced up to 300 m, but since then they have receded at annual rates of 5-10 m. Ice cover has decreased by about 240 km2 since the Little Ice Age maximum, with most of this loss occurring after the 19;!0s. Some small glaciers in the park have already vanished, and more are likely to disappear if the current trend continues. The record from Garibaldi Park is broadly synchronous with records of glaciers throughout the wlorld, suggesting a global forcing mechanism. Hemispheric temperature change can explain glacier behaviour during the last millennium. The Garibaldi record shows a relation to reconstructed Holocene sunspot activity, suggesting that changes in solar activity probably play an important role in global climate change.

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

Geochemistry and Geochronology of Eocene Forearc Magmatism on Vancouver Island: Implications for Cenozoic to Recent Plate Configurations in the Pacific Basin

Date created: 
2004
Abstract: 

The forearc area of the northern Cordillera preserves Tertiary magmatism in a semi-continuous belt from Alaska to Oregon. Vancouver Island is situated in a central position within this belt and contains five suites of Paleogene igneous rocks, three of which were studied for this thesis: the Mt. Washington intrusions, the Clayoquot intrusions and the Flores volcanic rocks. Eight new conventional ID-TIMS U-Pb zircon ages were obtained for the Mt. Washington and Clayoquot intrusions (5 1.2 +/- 0.4,48.8 +/- 0.5 Ma, 38.6 +/- 0.1, 38.6 +/- 0.2, 37.4 +/- 0.2, 36.9 +/- 0.2, 35.4 +/- 0.2 and 35.3+/- 0.3 Ma). The compositions of these three suites range from granite to tonalite. Some units display an adakitic trace element signature (commonly associated with slab melting) but have S-type character (indicative of sedimentary source rock) and are interpreted to be anatectic melts of subducted forearc sediment. Forward modelling of tectonic plate configurations in the Pacific basin from 53 Ma to the present was carried out to identify the most plausible plate configuration for forearc magmatism from Alaska to Oregon. Ridge-trench intersection and slab window formation were regarded as the most likely causes of the forearc magmatism, and were used to constrain the plate configurations. The model includes the recently proposed Resurrection plate in addition to the Kula, Farallon and Pacific plates. The modelling suggests that at -46 Ma, the Resurrection plate became segmented into two plates, the more northern of which is herein named the Eshamy plate. The plate model not only accounts for the majority of Tertiary forearc magmatism from Alaska to Oregon, but is also in close accord with Tertiary to Recent inboard magmatic and structural features.

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

Adakitic volcanism in Southern BC during the early Eocene: Isotopic and geochemical constraints from the Princeton Group

Author: 
Date created: 
2006
Abstract: 

The Princeton Group is an assemblage of volcanic and clastic sedimentary rocks in south-central British Columbia, and is part of the Challis- Kamloops belt that stretches from central British Columbia to the northwestern USA. Volcanics were deposited largely as composite-volcanoes, and are composed of calc-alkaline basaltic-andesite, andesite, dacite, and rhyolite. 4 0 ~ r / 3 9 ~ r dating indicates that magrnatism occurred during the Early to Middle- Eocene, from 53-47 Ma. 143~d/144~d measurements indicate that the f3G is primarily juvenile, with EN^^^ = 1.2-6.4. Princeton Group rocks geochemically resemble those of many rnodern continental arcs and have an 'adakitic' signature that extends throughout their compositional range. This signature is not derived from melting of subducted oceanic crust, but from an already enriched 'arc-like' source, hypothesized to be mafic dykes emplaced into the lithospheric mantle during Mesozoic magmatism. These dykes subsequently melted during lithospheric heating in the Eocene, probably caused by upwelling asthenosphere related to a slab-window or slabtear.

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

Comparison of episodic and non-episodic non-volcanic tremors in the northern Cascadia subduction zone

Date created: 
2006
Abstract: 

Sequences of non-volcanic tremor have been identified along the Nankai and Cascadia subduction zones [41, 151. The source mechanisms of tremor have been attributed to flow-induced rtesonance in fluid-filled conduits [23]. In northern Cascadia, transient surface deformation indicates that slow slip occurs every 13-1 6 months on the inter-plate boundary and landward of the locked zone. Elevated levels of tremor activity have been found to coincide spatially and temporally with slow slip episodes [46]. 1 image two tremor sequences: one which occurs during a slow slip episode (episodic) and another which occurs in between slip episodes (non-episodic). Episodic tremors migrate 150 km along strike from south to north and correlate with the subduction megathrust. Non-episodic tremors do not migrate, and are found mostly at 5-10 km depth within the continental crust. Non-episodic tremors could arise from readjustment of the crust following the preceding slow slip episode.

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

Sedimentology and hydrodynamics of strait-margin, sand-and-gravel beaches and shorefaces

Author: 
Date created: 
2010-09-07
Abstract: 

Sedimentological and ichnological analyses of three beaches and their associated shorefaces in the Juan de Fuca Strait was undertaken to develop a model for strait-margin beach-shoreface complexes. In the Juan de Fuca Strait,wave processes dominate deposition in the backshore, foreshore and upper shoreface. In the lower shoreface to offshore tidal energy is dominant. Sedimentological characteristics indicative of tidal currents dominated-depositionin the offshore and lower shoreface include the dominance of sand and the prevalence of current-generated structures. The offshore and lower shoreface are recognized ichnologically by biogenic structures attributable to the SkolithosIchnofacies. The term “tide-influenced shoreface” best describes thesen depositional environments.Biogenic-enhanced gravel transport was also observed in the offshore, lower and middle shoreface. Large kelp attached to clasts was moved parallel to the shoreline via tidal currents. It is estimated that with attached seaweed, thethreshold velocity for gravel transport is reduced by one order of magnitude.

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

An Integrated Field Mapping-Numerical Modelling Approach to Characterising Discontinuity Persistence and Intact Rock Bridges in Large Open Pit Slopes

Author: 
Date created: 
2012-12-04
Abstract: 

Field investigations were undertaken at three open pit mines and one major natural rock slope. Modified geotechnical field mapping techniques and remote sensing methods including LiDAR and photogrammetry were adapted for each site, in an effort to improve characterisation of discontinuity persistence and intact rock bridges. A fracture network engineering approach is proposed for trace mapping, with intensity factors to describe intact rock bridge trace intensity, R21, and blast-induced fracture intensity, B21.Results from the field investigations form the basis for a conceptual numerical modelling trial, where finite element, distinct element, and lattice-spring codes are used to investigate the role of persistence and rock bridges in large open pit slopes. A damage intensity approach is introduced to characterise the fracturing induced within a slope, D21. The results are used to make preliminary recommendations for improving field characterization and post-processing methods to assess discontinuity persistence and rock bridges in large open pits.

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

The nature of inclined heterolithic stratification in a mixed tidal-fluvial setting: depositional processes, sedimentology and ichnology, Middle Arm, Fraser River, Canada

Date created: 
2012-11-14
Abstract: 

The dynamic interplay of hydrodynamic processes in the subequally mixed tidal-fluvial Middle Arm, lower Fraser River dictates the nature of inclined heterolithic stratification (IHS) developed on channel bars. Intertidal zone and upper subtidal zone sediments are deposited in mm- to cm-scale, rhythmically alternating sand and mud beds, and this trend appears to continue to the lower subtidal part of the bar. Rhythmic laminasets are interbedded with dm-scale sand beds that reflect seasonal changes in river discharge. Surface samples from the intertidal zone are mud-dominated on the upstream and downstream ends of each bar, and the center of each bar is sandy such that bars exhibit a mud-sand-mud profile. Muddy bedsets in the intertidal zone are laterally extensive for up to 1 km in the along-strike direction, and muddy bedsets in the subtidal zone appear to extend for similar distances. Ichnological trends reflect the relative input and persistence of brackish-water in the channel. Burrow diversity, burrow density, and trace size increases in the seaward direction.

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