Colloquium Series Speakers

Dr. Gail Atkinson (Professor and Industrial Research Chair Department of Earth Sciences, University of Western Ontario)

Unnatural Tremors: The science of fracking and earthquakes, and why it matters

Date: Friday, November 16 2018  
Time: 1:30 pm – 2:30 pm
Location: BGS 0153

Abstract

There has been a significant increase in the rate of felt earthquakes in western Alberta and eastern British Columbia, which has been associated with hydraulic fracturing and wastewater disposal. The increased rate of seismicity and the potential for localized strong ground motions from very shallow events poses an increased hazard to critical infrastructure such as major dams – particularly for older high-consequence structures. I discuss the factors that affect the likelihood of damaging ground motions and examine their implications for hazard assessment and mitigation. A proposed strategy to achieve safety requirements for critical facilities contains elements of both avoidance and mitigation: (i) a "no-go" zone having a radius of ~5 km; and (ii) a monitoring-and-response protocol to track the rate of events at the M>2 level within 25 km, and adjust operational practices if required.

Dr. Paul Durkin (Assistant Professor, Department of Geological Sciences, University of Manitoba)

Revisiting fluvial meander-belt deposits with implications for interpretations of McMurray Formation

Date: Friday, November 9 2018  
Time: 1:30 pm – 2:30 pm
Location: BGS 0153

Abstract

Over the last decade, a series of insightful studies have highlighted fluvial meander-belt features in strata of the Cretaceous McMurray Formation, northeastern Alberta. High-quality 3-D seismic and image-log data reveal immense point bars, while detrital zircon studies have linked these features to a continental scale drainage system. These observations have prompted further investigation into meander-belt deposits, aimed at better understanding complex facies distributions, stratigraphic architecture, and paleoenvironmental interpretations to inform our understanding of bitumen-bearing units. This study utilizes data from the lower Mississippi River and outcropping fluvial deposits of the Western Canada Sedimentary Basin to inform characterization of the McMurray Formation at Surmont, Alberta. An unprecedented dataset consisting of 600 km2 of 3-D seismic and over 1000 well penetrations form the Cretaceous McMurray Formation in northeastern Alberta, Canada, provides a unique opportunity to characterize an ancient continental-scale river system. Paleochannels ranged from 475 to 1180 m wide and from 35 to 50 m deep, with meander-belt width-to-thickness ratios between 100:1 and 400:1. Reconstructed paleochannel migration patterns reveal the evolutionary history of seventeen individual meander-belt elements, including point-bar, counter-point bar, and their associated abandoned channel fill deposits, which have been mapped using core, microresistivity image logs, and seismic data. Results of the study show that intra-point-bar erosion surfaces bound accretion packages characterized by unique accretion directions, internal stratigraphic architecture, and lithologic properties. We provide evidence for channel-belt-edge confinement and development of a counter-point bar, as well as the deposition of side bars and preservation of a mid-channel bar during meander-bend abandonment. Analysis of changes in meander-belt morphology over time reveal a decrease in channel-belt width-to-thickness ratio and sinuosity, which we compare with observations from the lower Mississippi River and attribute to the landward migration of the paleo-backwater limit due to transgression of the Cretaceous Boreal Sea into the Alberta foreland basin.

Dr. Desmond Moser (Professor, Department of Earth Sciences, Department of Geography, University of Western Ontario)

Atomic Worlds; 3D Maps of Time in Minerals from Planetary Crusts

Date: Friday, November 2nd 2018  
Time: 1:30 pm – 2:30 pm
Location: BGS 0153

Abstract

Nano-scale techniques are revealing vestiges of the past once thought lost to geologic time.
Among these techniques is atom probe tomography (APT) - a relatively new method in
geoscience that is advancing the field of geochronology in several ways. APT requires the
fabrication of a needle hundreds of nanometres in length using a focused ion beam SEM. The
surface of the needle is then ionized and evaporated with a pulsed laser, layer by layer, in a
time-of-flight mass spectrometer with a positional ion detection system that allows atomic and
sometimes isotope identification as well as the reconstruction of the original positions of
atoms. The result is a three-dimensional atom-scale map that, when derived from U-Pb
accessory minerals, allows the simultaneous measurement of isotopic ratios and imaging of
chemical nanostructures, sometimes defined by the geochronology isotopes themselves. I’ll
show some of the phenomena that are being revealed with this technique using our group’s
results for ancient zircon and baddeleyite from the Earth and Mars. When combined with
correlative microscopy techniques such as electron backscaLer diffraction (EBSD), we can use
this “Microstructural Geochronology” to identify diffusion processes that signal otherwise
hidden tectonic, impact and fluid events in planetary history. Potential applications to
environmental research and resource analysis will also be presented.

Dr. Carl Mitchell (Associate Professor, Department of Physical and Environmental Sciences, University of Toronto Scarborough)

Monitoring gaseous mercury with a precise, accurate and inexpensive sampler and potential applications to the Menimata Convention on Mercury

Date: Friday, October 26th 
Time: 1:30 pm – 2:30 pm
Location: BGS 0153

Abstract
The Minimata Convention on Mercury is a relatively new global treaty for protecting both human health and the environment from the adverse effects of mercury. Implementing and evaluating the effectiveness of the Minamata Convention requires (1) the identification and characterization of mercury sources to the atmosphere, (2) the long term monitoring of mercury in the vicinity of identified sources to assess effectiveness of local efforts to reduce emission to the atmosphere, and (3) long term monitoring at background sites to assess effectiveness of regional and global efforts to reduce emissions. This talk will describe our group’s recent invention and rigorous testing of a precise, accurate and inexpensive passive air sampler for gaseous mercury that can play an important role in meeting all of these Convention effectiveness goals. The talk will include results from a global-scale calibration exercise, from laboratory experiments (including at Western’s Biotron facility) to quantify the effects of meteorological parameters on sampler performance, and urban and mining site case studies outlining the sampler’s potential for identifying fugitive sources and estimating emissions. Future and ongoing work to better measure surface emissions and to use the samplers for stable isotope-based source attribution will also be discussed.

Dr. Katsu Goda (Associate Professor & Canada Research Chair in Multi-Hazard Risk Assessment, Western University)

"Stochastic Representation of Earthquake Rupture: Applications in Earthquake and Tsunami Research"

Date: Friday, September 28th 
Time: 1:30 pm – 2:30 pm
Location: BGS 0153

Abstract
Earthquake rupture due to mega-thrust subduction events is a complex phenomenon and uncertainties associated with such rupture processes have paramount influence on ground shaking and tsunami. Representation of earthquake sources in seismic-tsunami hazard-risk analysis has major implications on seismic hazard and tsunami hazard maps, and thus risk mitigation and management measures against catastrophic earthquake events critically depend on how such hazard and risk analyses are performed.

The talk introduces a new stochastic modelling technique for earthquake rupture and presents a few applications to earthquake and tsunami research. The method combines stochastic synthesis of earthquake slip and probabilistic earthquake source scaling relationships. The new method is implemented to carry out novel earthquake-tsunami multi-hazard impact assessments and to characterize earthquake-triggered ground deformation probabilistically. The research tools provide innovative means to evaluate the cascading multi-hazards and compounding multi-risks.

 

Dr. Merrin Macrae (Assistant Professor, Department of Geography & Environmental Management, University of Waterloo)

"The Effects of Hydoclimatic Conditions on Biogeochemical Processes in Natural and Disturbed Landscapes"

Date: Friday, September 21st 

Time: 1:30 pm – 2:30 pm

Location: BGS 0153 

Abstract:
The mobilization of contaminants in the environment is driven by the combination of supply and transport mechanisms, both of which vary in space and time, and are impacted by climatic variability and anthropogenic disturbance. The successful management of sustainable water resources and ecosystems requires the use of an ecohydrological approach, where both ecological and hydrological processes are considered, as well as their interactions. This seminar will provide an overview of my research group’s recent progress in this field.  My lab group seeks to (1) quantify nutrient biogeochemical processes in a range of environments; and, (2) characterize how nutrient dynamics in the environment and ecosystem function are affected by hydrology and hydroclimatic change (natural or disturbance). Our recent progress in three areas will be highlighted: (1) Spatio-temporal patterns in hydrologic and biogeochemical export from agricultural areas; (2) Effects of hydrologic change and disturbance on nutrient transformations and mobility in wetlands; and (3) Effects of climate change on the hydrology and biogeochemistry of ponds at high latitudes.