Grant: Discovery Grants Program - Individual

I am interested in how Earth's landscapes have evolved over different timescales. Two chronological methods for determining rates and timing of surface processes at timescales between thousands and hundreds of millions of years are revolutionizing the way Earth Scientists analyse landscape evolution. Terrestrial cosmogenic nuclides (TCNs) produced when cosmic rays interact with exposed minerals in the upper few metres of Earth's surface are used to directly date when landscape change events have occurred, such as the timing of past glaciations, seismic offset of strain markers such as bedrock surfaces or alluvial fans, or the eruption of volcanoes. Exposure ages of incised canyon walls and bedrock strath terraces can provide information about the variability in incision rates of selected reaches of streams. Additionally, TCNs can be used to estimate short- and long-term averaged erosion rates of spatial scales from individual mountain peaks to entire stream catchments over timescales of thousands to millions of years. The second method, (U-Th-Sm)/He low temperature thermochronology, is used to estimate the cooling history of a rock on Earth's surface since it was exhumed from depths of two to four kilometres (minerals may cool at variable rates as they ascend). The technique is applicable over timescales of tens of thousands to hundreds of millions of years, and can also be used as a tephrochronology tool (to date minerals in pre-historic volcanic ash). The advantage in coupling both methods is that a more complete understanding of landscape evolution may be attained, in order to address questions such as: (1) What is the history of earthquake faulting in the Andes? (2) What is the erosion history of the Canadian shield (potential nuclear waste repository)? (3) What is the evolutionary history of the expansive physiographic surfaces throughout the Central Arctic? Answers to this question help reduce risk to petroleum and mineral exploration in the Arctic. The facilities for these techniques have been established at Dalhousie and my research program will help train undergraduate and graduate students, technical staff, and visiting researchers in aspects of isotope and environmental geochemistry.