It has been hypothesized that authigenic carbonate minerals, formed within the pore spaces of marine siliciclastic formations during early diagenesis, may have had a substantial influence on the global carbon cycle, particularly in times of low oxygen in Earth history. According to this idea, alkalinity is generated via anaerobic organic matter degradation, resulting in carbonate oversaturation and the precipitation of low δ13C carbonate cements. If a substantial amount of 13C-depleted carbonate was sequestered in this authigenic sink, the δ13C of dissolved inorganic carbon (DIC) in the global ocean would be driven to more positive values without significant organic carbon burial - a signal which would be recorded in marine carbonates. Research presented herein tests this hypothesis from newly acquired lithostratigraphic and coupled stable carbon and oxygen isotope data of Upper Devonian limestone and black shale formations preserved within the Western Canada Sedimentary Basin. The Late Devonian includes a mass-extinction event, and is characterized by pervasive ocean anoxia and a dramatic reduction in platformal carbonate sediment deposition. As such, it has been hypothesized to represent an ideal time for the emergence of an active authigenic carbonate sink. Results show that both basinal shale (Besa River and Exshaw formations) and platform carbonates (Wabamun Group and its equivalents), record a δ13C signal that is within the expected range of Devonian seawater (3‰ to -2‰), signifying that precipitated authigenic carbonate had no influence on the isotopic composition of DIC. It was observed, however, that evaporitic depositional settings can accumulate carbonate sediment with low δ13C values (down to -8.4‰), potentially caused by local water column organic matter respiration during prolonged water-mass residence in a restricted marginal marine setting. If such depositional environments were globally pervasive, such as during during global sea-level lows, it is plausible that the carbon isotope mass balance would be affected. / Graduate / 2021-06-18

The Upper Devonian-Lower Mississippian Bakken Formation has recently become a prolific producer of light gravity oil in southeastern Saskatchewan since the advent of horizontal drilling and multi-stage hydraulic fracture technologies, which has resulted in an increase in geological studies within the area. However, the Bakken Formation of west-central Saskatchewan has been producing heavy oil since the 1950s, and has comparatively received much less attention than its southeastern counterpart. The Bakken Formation is the youngest member of the Three Forks Group and unconformably overlies the Big Valley Formation. In west-central Saskatchewan, the Bakken Formation can be conformably overlain by the Mississippian carbonates of the Madison Group or unconformably overlain by the Lower Cretaceous Mannville Group. A tripartite subdivision is applied to the Bakken Formation, with a mixed clastic/carbonate Middle Member deposited between Lower and Upper Black Shale Members. Based on detailed core description, eight facies have been defined for the Bakken Formation of west-central Saskatchewan: Facies 1 (Lower and Upper Black Shale members), Facies 2 (bioturbated siltstone/sandstone), Facies 3 (wave-rippled sandstone), Facies 4 (bioclastic grainstone), Facies 5 (interbedded mudstone, siltstone, and very fine-grained sandstone), Facies 6 (very fine- to fine-grained sandstone), Facies 7 (bioturbated siltstone/sandstone), and Facies 8 (massive and brecciated siltstone). Deposition of the Bakken Formation in west-central Saskatchewan occurred under either open-marine or marginal-marine conditions. Facies association 1 (open-marine interval), which is made up of F1 through F4, is characterized by the distal Cruziana Ichnofacies. It was deposited within a wave-dominated shallow-marine depositional environment. Facies association 2 (marginal-marine interval), which is comprised of F5 through F8, shows scarce biogenic structures, most likely as a result of brackish-water conditions. Geological mapping (structure surface and isopach) of the facies and facies associations has aided in illustrating their lateral distribution. However, mapping of the overlying Mississippian carbonates and sub-Mesozoic unconformity shows that post-Mississippian erosion was a controlling factor in the distribution and preservation of Bakken Formation deposits, which creates uncertainty when interpreting geological maps and stratigraphic cross-sections. Although post-Mississippian erosion causes problems when reconstructing the depositional history and stratigraphic architecture of the Bakken Formation, it illustrates the importance of not performing stratigraphic studies within a vacuum, only focusing on the formation of interest. Rather, underlying and overlying units must be studied to see whether or not the unit of interest’s deposition and distribution has been affected by pre- and post-depositional events.

Over a decade ago, it was discovered that the earth’s natural seismic wavefields, propagating as seismic noise, can be processed using correlation methods to produce surface waves, similar to those generated by earthquakes. This discovery represents a paradigm shift in seismology and has led to several tomographic studies of earth structures, at different scales and resolutions, in previously difficult-to-study areas around the world. This PhD dissertation presents research results on multi-scale and multi-purpose applications of ambient seismic noise wavefields under three topics: (1) Imaging of sedimentary basins and sub-basin structures in eastern and western Canada using ambient seismic noise, (2) Combining measurements from ambient seismic noise with earthquake datasets for imaging crustal and mantle structures, and (3) Temporal variation in cultural seismic noise and noise correlation functions (NCFs) during the COVID-19 lockdown in Canada. The first topic involved imaging the sedimentary basins in eastern and western Canada using shear wave velocities derived from ambient noise group velocities. The results show that the basins are characterized by varying depths, with maximums along the studied cross-sections in excess of 10 km, in eastern and western Canada. Characteristics of accreted terranes in eastern and western Canada are also revealed in the results. A seismically distinct basement is imaged in eastern Canada and is interpreted to be a vestige of the western African crust trapped beneath eastern Canada at the opening of the Atlantic Ocean. In western Canada, the 3D variation of the Moho and sedimentary basin depths is imaged. The thickest sediments in eastern Canada are found beneath the Queen Charlotte, Williston and the Alberta Deep basins, while the Moho is the deepest beneath the Williston basin and parts of Alberta basin and northern British Columbia. For the second topic, I worked on improving the seismological methodology to construct broadband (period from 2 to 220 s) dispersion curves by combining the dispersion measurements derived from ambient seismic noise with those from earthquakes. The broadband dispersion curves allow for imaging earth structures spanning the shallow crust to the upper mantle. For the third topic, I used ambient seismic data from the earlier stages of the COVID-19 pandemic to study the temporal variation of seismic power spectra and the potential impacts of COVID-19 lockdown on ambient NCFs in four cities in eastern and western Canada. The results show mean seismic power drops of 24% and 17% during the lockdown in eastern Canada, near Montreal and Ottawa respectively and reductions of 27% and 17% near Victoria and Sidney respectively. NCF signal quality within the secondary microseism band reached maximum before the lockdown, minimum during lockdown and at intermediate levels during the gradual reopening phase for the western Canada station pair. / Graduate