Retrogressive thaw slumps are one of the most dramatic thermokarst landforms in periglacial regions. This thesis investigates the impacts of two of the largest hillslope thaw slumps on the geochemistry of periglacial streams on the Peel Plateau, Northwest Territories. It aims to describe the inorganic geochemistry of runoff across active mega-slumps, impacted and pristine tundra streams, as well as that of the ice-rich permafrost exposed in the slump headwalls. Slump runoff is characterized by elevated suspended sediments (911 g/L), high conductivity (2700 µS/cm), and high SO42- ( up to 2078 ppm). The runoff originates as a solute-rich meltwater near the slump headwall, and leaches and re-dissolves soluble salts (e.g., gypsum) as it flows along the mudflow. Conductivity increases until the runoff mixes with pristine tundra streams, diluting the slump runoff signal. SO42-/Cl- is used as a tracer to isolate the slump runoff signal in impacted waters, and suggests that the contribution of slump runoff to the Peel River has been increasing since the 1960s.

Retrogressive thaw slumps are one of the most dramatic thermokarst landforms in periglacial regions. This thesis investigates the impacts of two of the largest hillslope thaw slumps on the geochemistry of periglacial streams on the Peel Plateau, Northwest Territories. It aims to describe the inorganic geochemistry of runoff across active mega-slumps, impacted and pristine tundra streams, as well as that of the ice-rich permafrost exposed in the slump headwalls. Slump runoff is characterized by elevated suspended sediments (911 g/L), high conductivity (2700 µS/cm), and high SO42- ( up to 2078 ppm). The runoff originates as a solute-rich meltwater near the slump headwall, and leaches and re-dissolves soluble salts (e.g., gypsum) as it flows along the mudflow. Conductivity increases until the runoff mixes with pristine tundra streams, diluting the slump runoff signal. SO42-/Cl- is used as a tracer to isolate the slump runoff signal in impacted waters, and suggests that the contribution of slump runoff to the Peel River has been increasing since the 1960s.

In March of 1987, the Geologic Survey of Canada conducted a major seismic refraction experiment in the Mackenzie Delta-Southern Beaufort Sea-Northern Yukon area. This study involves the analysis of a portion of the resulting data set. A 2D velocity profile through the Richardson Mountains of the northern Yukon has been constructed using raytracing to model the travel-times and amplitudes. The line is approximately 320 km long, running from a shotpointon the Eagle Plains in the south to one 50 km offshore in Mackenzie Bay to the north, with an average receiver spacing of 3.5 km. An additional shotpoint is located at Shingle Point, on the shore of Mackenzie Bay. A series of four sedimentary basins separated by major structural highs produces a complex basement structure. Two distinct upper crustal layers were modelled, a 5.95 km/s layer overlying a 6.3 km/s layer, as well as a lower crustal layer with a velocity of 7.25 km/s. Crustal velocity gradients are low (≤ 0.005 s⁻¹). The 6.3 km/s layer pinches out beneath the Beaufort-Mackenzie Basin in the north, accompanied by a thinning of the lower crust from a thickness of 20 km in the south to less than 10 km beneath MB. This results in the crust as a whole thinning from a thickness of 50 km under the Richardson Mountains to only 40 km under the Beaufort-Mackenzie Basin. The velocity of the upper mantle is 7.95 km/s. The modelling of shear wave arrivals indicate Poisson's ratios of 0.23 ±0.02 in the upper crust and 0.25 + 0.02 in the lower crust. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

This thesis applies a novel method of change detection, the Landsat Image Stack Trend Analysis method to the monitoring of retrogressive thaw slumps in the Richardson Mountains, NWT. This method represents a significant improvement upon previous methods of thaw slump monitoring, which utilized air photos and high-resolution satellite imagery. This method applies Tasseled Cap brightness, wetness and greenness indices to Landsat TM/ETM images acquired between 1985 and 2011 and analyzes the temporal change of each pixel for the different indices values. This method is useful in retrogressive thaw slump monitoring in two ways. First, by creating a map showing the linear change over time from 1985 to 2011, retrogressive thaw slumps can be easily identified, as they are more dynamic than the surrounding tundra. In total, 251 thaw slumps were identified within an area of roughly 18 000km2. Second, thaw slump activity, from initiation, growth and stabilization can be studied by plotting the annual vegetation index pixel values of adjacent pixels in a thaw slump. This method allows for the efficient extraction of annual thaw slump headwall retreat rates, provided the availability of cloud-free imagery. The retreat rates of 16 slumps were extracted, which were found to have an average annual retreat rate of 11.8 m yr-1.

This thesis applies a novel method of change detection, the Landsat Image Stack Trend Analysis method to the monitoring of retrogressive thaw slumps in the Richardson Mountains, NWT. This method represents a significant improvement upon previous methods of thaw slump monitoring, which utilized air photos and high-resolution satellite imagery. This method applies Tasseled Cap brightness, wetness and greenness indices to Landsat TM/ETM images acquired between 1985 and 2011 and analyzes the temporal change of each pixel for the different indices values. This method is useful in retrogressive thaw slump monitoring in two ways. First, by creating a map showing the linear change over time from 1985 to 2011, retrogressive thaw slumps can be easily identified, as they are more dynamic than the surrounding tundra. In total, 251 thaw slumps were identified within an area of roughly 18 000km2. Second, thaw slump activity, from initiation, growth and stabilization can be studied by plotting the annual vegetation index pixel values of adjacent pixels in a thaw slump. This method allows for the efficient extraction of annual thaw slump headwall retreat rates, provided the availability of cloud-free imagery. The retreat rates of 16 slumps were extracted, which were found to have an average annual retreat rate of 11.8 m yr-1.