Base de données de recherche des TNO

étiquettes: physical sciences, remote sensing, glacial deposits, deglaciation

Objectif(s): To improve the chronology of the retreat of the Laurentide Ice Sheet from the eastern foot of the Mackenzie Mountains and the Mackenzie River valley that began around 14,000 years ago, and to gain better understanding of the dynamics of how the ice left the region and development of large lakes that occupied the valleys.

Description du projet: In this project, the research team aim to improve the chronology of the retreat of the Laurentide Ice Sheet from the eastern foot of the Mackenzie Mountains and the Mackenzie River valley that began around 14,000 years ago, and to gain better understanding of the dynamics of how the ice left the region and development of large lakes that occupied the valleys. The research team will attempt to quantify the overall amount and the rate of ice mass loss in the northwest sector of the Laurentide Ice Sheet during the early stages of deglaciation. The team further aim to reconstruct the evolution of the drainage along the northwest Laurentide margin and to reconstruct the evolution of glacial Lakes McConnell and Mackenzie that filled the Mackenzie valley prior to development of the Mackenzie River. The fieldwork is informed by mapping from remotely-sensed data which identifies sites of interest for further field study. The research team will collect samples to date the timing of the ice sheet retreat and lake formation and drainage. These are either radiocarbon dating (samples consist of recovered organic material, boulder samples for cosmogenic exposure dating (samples consist of rock samples collected from continuously-exposed rock surfaces, mostly moraine or erratic boulders), or optically stimulated luminescence (samples consist of river sand collected from sedimentary sections). There is virtually no impact from these sampling activities on the landscape; boulders, of which we may sample up to 30, have the upper 2-3 cm of rock chiselled or cut from their surface in an area up to 15 x 15 cm. A description of the sedimentary architecture in exposed river banks that allows for reconstructing the local sedimentary stratigraphy will be made.. Samples for radiocarbon dating and characterization from these areas consist of sediment samples up to 1L in size. Shallow (<6 m) permafrost cores will be collected at sites where frozen lake sediment is evident. A lightweight, 2-man auger system (post-hole auger) will be used to drill the 5” diameter cores. The uppermost soil profile will be set aside and used to cap the drill hole to mitigate land disturbance. All materials brought in are carried out from the sites. This research will lead to better knowledge about the natural history of the region at the time prior to and around the first human settlement in the area. And through the work on the glacial lakes that existed in the area, an improved understanding of permafrost dynamics in the region. Copies of all research resulting from this project will be supplied to the Aurora Research Institute and to communities as Aurora thinks appropriate. A public presentation could be arranged if there is interest from any of the concerned communities. The fieldwork for this study will be conducted from July 10, 2018 to August 5, 2018.