In the east-central Alberta, isopach values of the McMurray Formation measured from the overlying Wabiskaw Marker datum show that paleotopographic relief on the sub-Cretaceous Unconformity is express by three paleo-valleys carved into the Grosmont-Wainwright Highlands. The paleo-valleys are named herein as: Grouse, Quail, and Ptarmigan. Mineralogical analysis of McMurray Formation sandstones in the paleo-valleys resolves subtle but recognisable vertical and spatial variations in composition. Feldspar contents decrease and lithic contents increase with stratigraphic depth. Based on petrographic analyses, McMurray Formation sandstones are sourced dominantly from a continental-scale drainage across the craton, with secondary input from uplifted sedimentary strata in the west as well as from the Canadian Shield in the east. Probable, paleo-tributaries can be superimposed on isopach maps of the McMurray Formation that, when coupled with net-sand maps, appear to bisect the highlands, suggesting that the Grosmont-Wainwright did not prevent some Cordillera sediment from entering the Ptarmigan and Quail paleo-valleys. This Cordillera-derived sediment was delivered via Edmonton Valley, and is calculated to constitute approximately 35% of the sediment supplied.
The response of a fractured bedrock aquifer in a temperate region (Gulf Islands, British Columbia) to heavy rainfall events is characterized. Of the 14 provincial observation wells with hourly groundwater level data, wells with shallow water levels showed pronounced responses to heavy rain events, a lag less than 12 hours, and a strong correlation to all rain events. Rises in groundwater level at Well 125 appear to be better related to all rain events than exclusively heavy rain during summer, and decrease as the rainfall intensity increases. Thermal infrared images and δ18O and δ2H composition for precipitation and seepage indicate an increase in seepage in the late fall and winter. Solution of the Green-Ampt equation for rainfall events of varying magnitude suggest that an increase in winter rainfall intensity leads to more surface ponding and overland flow. The projected occurrence of more heavy rain events in the future may result in lower net recharge.
Unit PR1 of the lower Fifteenmile group and the Pinguicula Group are exposed in Ogilvie and Wernecke mountains, Yukon, Canada. Unit PR1 records deposition of turbiditic interbedded sandstone and mudstone with scattered carbonate olistoliths. The Pinguicula Group records deposition of non-cyclic siliciclastic and carbonate strata on low-energy slopes affected by rare high-energy deposits. The Pinguicula Group comprises three newly formalised formations: the Mount Landreville, Pass Mountain, and Rubble Creek (formerly units A, B, and C, respectively). The older unit PR1 has a near-unimodal detrital zircon population with an age of 1499 ± 2.7 Ma and εNd(t) values from -8.17 to 3.92. Overall, detrital zircon data from the Pinguicula Group display a polymodal detrital zircon population with a maximum age of <1322 ± 23 Ma and εNd(t) values from -1.55 to 1.12. C-isotopic analyses from the Pinguicula Group record average δ13C values ranging from -0.64 to +1.6‰ Vienna Pee Dee Belemnite (VPDB). Stratigraphic correlations between the Pinguicula Group in the Wernecke and Hart River inliers have been confirmed using lithostratigraphy, combined with detrital zircon U-Pb geochronology, Sm-Nd, and C-isotope signatures. The Pinguicula Group and unit PR1 are no longer considered correlative based on differences in detrital zircon signatures and Sm-Nd isotopic data. Detrital zircon ages from unit PR1 fall into the North American Magmatic Gap (NAMG; 1610-1490 Ma) and therefore sediment in unit PR1 is interpreted to have been from the Mt. Isa inlier in northeastern Australia. The PR1 basin may have been deposited as early as 1460 Ma on Laurentia’s northwestern margin, coincident with the Belt-Purcell, Yankee Joe/Defiance, and Trampas basins that formed during the break-up of supercontinent Columbia. These basins derived some or all of their sediment from Australia and the Mawson continent. Younger Mesoproterozoic strata, deposited after 1.45 Ga, including the Missoula Group and Marqueñas Formation, lack NAMG-aged zircons and instead record a shift in sediment provenance to southern Laurentia as north Australia and the Mawson continent rifted from Laurentia’s western margin. The Pinguicula Group (<1322 Ma) was probably fed from southern Laurentian Granite-Rhyolite provinces with NAMG-aged zircons recycled from older Mesoproterozoic strata.
Bioturbated sediments representing distal expressions of paralic depositional environments are increasingly being exploited for hydrocarbons in the super-giant Pembina Field (Cardium Formation), Alberta, Canada. These strata were previously considered unproductive due to limited vertical and horizontal connectivity between permeable beds. In these “tight oil” plays (0.1 – 10 md), pressure decay profile permeametry data indicate that sand-filled burrows provide vertical permeable pathways between bioturbated and parallel laminated sandstone beds in the central, north-east and north-west parts of the field. This relationship enables the economic exploitation of hydrocarbons via horizontal drilling and multi-stage hydraulic fracturing. As the exploitation of bioturbated strata progresses in the Pembina Field, additional primary targets are being sought out, and horizontal waterflooding is being considered in areas where current horizontal wells exist. Proximal to historical produced conventional targets, reservoir analyses indicate that areas where the bioturbated facies average permeability lies between 0.35 mD and 0.85 mD and sandstone isopach thicknesses are between 0.25 m and 2.5 m should be targeted in east-central Pembina.
Seismic interferometry is a technique by which the Green’s function or impulse response between two receivers is recovered through the cross-correlation of the transmission responses recorded by those receivers. This technique has found several applications, including the generation of virtual shot gathers from ambient seismic noise for use in seismic reflection processing. In March of 2013, 336 receivers were deployed over the volcanogenic massive sulphide (VMS) deposit found at the Lalor mine in Manitoba, Canada. Approximately 300 hours of ambient seismic noise was recorded for the purpose of testing the effectiveness of seismic interferometry in imaging a crystalline rock environment. A time-domain beamforming algorithm was implemented to determine the locations of the sources present during recording. The results indicate that the vast majority of the recorded noise originated from mine and ventilation shafts located at the Lalor mine. Synthetic experiments were conducted to determine the effects such a source distribution would have on the application of seismic interferometry in the presence of dipping reflectors. The experiments show that if sources are located only on one side of a receiver line, the dip and lateral extents of reflectors will not be imaged properly. A technique involving beamforming and F-K filtering was developed to remove surface wave noise originating from near-field sources. Using this technique, the raw data was processed into virtual shot gathers free of surface wave noise. Virtual shot gathers were generated along 4 of the receiver lines and processed as separate 2-D reflection datasets. The resulting reflection profiles are compared against coincident DMO-stacked data from a larger 3-D active seismic survey conducted over the Lalor mine. Using this comparison in conjunction with knowledge of the local geology, events recovered in the passive reflection profiles are interpreted as either real reflections or spurious events, and possible explanations of their origin are given.
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.
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.
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.
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.
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.