This study presents new ages for the northwest section of the Laurentide Ice Sheet (LIS) glacial chronology from material recovered from two retrogressive thaw slumps exposed in the Richardson Mountains, Northwest Territories, Canada. One study site, located at the maximum glacial limit of the LIS in the Richardson Mountains, had calcite concretions recovered from aufeis buried by glacial till that were dated by U/Th disequilibrium to 18,500 cal yr BP. The second site, located on the Peel Plateau to the east yielded a fossil horse (Equus) mandible that was radiocarbon dated to ca. 19,700 cal yr BP. These ages indicate that the Peel Plateau on the eastern flanks of the Richardson Mountains was glaciated only after 18,500 cal yr BP, which is later than previous models for the global last glacial maximum (LGM). As the LIS retreated the Peel Plateau around 15,000 cal yr BP, following the age of the Tutsieta phase, we conclude that the presence of the northwestern margin of the LIS at its maximum limit was a very short event in the western Canadian Arctic.

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Managing fluid fine tailings (FFT) present a major cause of industrial and environmental concerns in oil sands surface mining production. A potential management solution is to dewater and cap the FFT solids for use in land reclamation. A 16-week greenhouse study was conducted to assess whether FFT centrifuge cake with caps of various reclamation soil mixes (forest floor mineral mix, peat mineral mix, and a mixture of both) and depths (0, 5, 10 and 20 cm) would support growth of trembling aspen (Populus tremuloides – native broadleaf tree) and beaked willow (Salix bebbiana – native broadleaf shrub). Beaked willow had a much greater survival rate (100%) when grown directly in FFT cake compared to trembling aspen (16.7%). Plants grown directly in FFT cake were negatively impacted by high water content, low nitrate supply rates, and high metal concentrations with beaked willow seedlings having 10 times higher foliar concentrations of Al, Cr, and Ti compared to any other treatments. Adding soil caps substantially increased aboveground biomass for both species but differences among soil cap types and depths did not have as significant of an effect on plant growth. Results from this study show that capping FFT substantially improves woody plant growth, and Salix bebbiana and Populus tremuloides are potentially suitable species for tailings reclamation.

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Perennially flowing groundwater discharges along a 15‐km section of the Fishing Branch River, Yukon causing open water during winter and numerous discrete springs near Bear Cave Mountain. Groundwater flow occurs in karstified marine carbonate rocks as well as in alluvial river talik(s). The PCO2 and δ13C indicate groundwater dissolves CO2 during recharge in organic soils and weathers limestone in the aquifer. These analyses show three groundwater chemistry groups and variability in surface water chemistry. The variations in water chemistry are related to differences in the rocks exposed in the recharge area. The δ18O and δ2H results show that groundwater represents approximately the annual average of precipitation based on samples collected in the region. Noble gases were used to determine that the recharge temperature lies between 0 and 5 °C which suggests that recharge happens during the summer. Groundwater ages, calculated using 3H‐3He dating, were found to be between 0 and 17.7 years. River discharge was measured during spring and summer under different water‐level conditions. Winter baseflow was calculated based on summer discharge measurements and the width of the river channel in winter. Although river flow decreases in winter, groundwater discharge maintains open water. Copyright © 2012 John Wiley & Sons, Ltd.

Argon, krypton and xenon have different solubilities in water, meaning their ratios in water are different from those in atmospheric air. This characteristic is used in a novel method to distinguish between ice bodies which originate from the compaction of snow (i.e. buried snow banks, glacial ice) vs. ice which forms from the freezing of groundwater (i.e. pingo ice). Ice which forms from the compaction of snow has gas ratios similar to atmospheric air, while ice which forms from the freezing of liquid water is expected to have gas ratios similar to air-equilibrated water. This analysis has been conducted using a spike dilution noble gas line with gas extraction conducted on-line. Samples were mixed with an aliquot of rare noble gases while being melted, then extracted gases are purified and cryogenically separated. Samples have been analysed from glacial ice, buried snow bank ice, intrusive ice, wedge ice, cave ice and two unknown ice bodies. Ice bodies which have formed from different processes have different gas ratios relative to their formation processes.

This three-year meso-scale greenhouse study used 55-gallon columns to evaluate the survival and growth of boreal wetland communities planted on centrifuge (CF) tailings and co-mixed (CM) tailings capped with different reclamation cover soil capping designs. The CF tailings were capped with a shallow layer (10 and 30 cm) of peat reclamation material (PRM) and the CM tailings were capped with a shallow layer (5 cm) of PRM above (15 or 35 cm) of reclamation subsoil (till). After three years, plant survival and growth on CF tailings showed significant improvement with a 10 cm PRM cap compared to the uncapped tailings, and plants growing on a 30 cm PRM cap outperformed those on the 10 cm PRM cap. Plant growth on CM tailings was significantly improved with a soil cover containing 5 cm PRM and at least 15 cm till. Among the seven native wetland species included in this study, the top performing species survival and above-ground biomass were Salix bebbiana, Scirpus microcarpus and Carex aquatilis.