NWT RESEARCH DATABASE

Regions: Dehcho Region

Tags: physical sciences, paleoclimatology, glaciers, radionuclides

Objective(s): To date the formation of end moraines in the Northwest Territories using methods of Terrestrial Cosmogenic Nuclide (TCN) dating to develop a chronology of glacier change in this region.

Project Description: This licence has been issued for the scientific research application No.5303. The primary objective of this study is to date the formation of end moraines in the Northwest Territories using methods of Terrestrial Cosmogenic Nuclide (TCN) dating to develop a chronology of glacier change in this region. This chronology will be used to assess glacial response to Holocene climate with aims to elucidate if glaciers responded in concert with other western Canadian Cordillera alpine glaciers or if different climate mechanisms influence glaciers at high latitudes. The derived dataset of numerical apparent exposure ages will be compared with previously determined moraine ages in this region for presence of outliers to investigate if these moraines represent true ages or an erroneous symptom of geologic scatter. The research team will visit the relevant end moraines that front outlet glaciers in the study area. The ages of the moraines will be determined through TCN dating, a numerical dating technique that allows rock samples with a specific mineral content to be dated for exposure to the flux of cosmic rays emitted by the sun. The relevance of TCN dating for constraining glacier chronologies is based upon the assumption that fresh rock surfaces are created at the bed of glaciers which are concealed from exposure to the flux of cosmic rays from the sun. The duration of exposure for a morphologically relevant rock can be used as a direct proxy for the timing of glacier ice advance. The team will target quartz-rich bedrock for sampling as quartz produces the relevant radioactive isotopes Carbon-14 and Beryllium-10 for dating young samples. Samples will be collected using a gas-powered rock saw used in conjunction with a hammer and chisel to collect approximately 1 kg of sample from each boulder. This process will leave a roughly 15 x 20 cm patch of cleaner-looking rock on top of the boulders which will soon be repopulated by lichens. Master’s student Caleb Mathias will extract and purify quartz from the rock samples at Columbia University under supervision and prepare sample targets for Accelerator Mass Spectrometry (AMS) measurement of the C-14 and Be-10 isotopes at the Lamont-Doherty Earth Observatory. The numerical apparent exposure ages generated by the terrestrial chronology will be compared to regional-to-hemispheric climate proxies to evaluate the climate sensitivity of the glaciers in the study area. Expected project outputs include a public thesis defense, a published graduate thesis, and a scientific journal publication. Digital photographs of sampled boulders and study sites will be taken. Geographic Information System-based maps will be prepared featuring relevant findings for use in the expected publications. In addition, the team would also be happy to provide a scientific talk to Parks staff and/or local communities. The fieldwork for this study will be conducted from August 1, 2022 to August 31, 2022