Diamond Geology and Exploration

GEM-2 Glacial Synthesis Project: Highlights Of 2018 Field Activities in the Healey Lake Area, Northwest Territories and Nunavut

Tuesday, November 20, 2018 - 16:20 to 16:39 Theatre 1


J.E. Campbell (Presenting)
Geological Survey of Canada

P.X. Normandeau
NWT Geological Survey

P-M. Godbout
Université du Québec à Montréal

I. McMartin
Geological Survey of Canada

Targeted surficial geological studies were conducted this past summer in an area between Aylmer Lake, Northwest Territories (NWT) and the western edge of the Thelon Wildlife Sanctuary in the NWT and Nunavut. Fieldwork focused on questions related to the nature of the glacial landscape, landforms and associated surficial materials, the chronology of glacial and deglacial events, and glacial transport - dispersal characteristics in this largely unmapped west-central region of the Keewatin Sector of the Laurentide Ice Sheet (LIS).

Field observations, till sampling and striation mapping indicate the landscape mirrors the complex nature of its glacial history. Spatial variability in geomorphology, surface material composition, thickness and degree of weathering results from changes in substrate lithology, basal thermal conditions (warm-based to cold-based) and paleo-ice flow dynamics. The landscape of the central region around Healey Lake is bedrock-controlled; dominated by low relief, weathered and frost-shattered outcrops, block fields, with thin veneers of till and boulders reminiscent of relict terrains preserved under non-erosive, cold-based ice conditions. Small patches of warm-based ice terrains with glacially moulded and polished outcrops recording an older southwest flow, and thicker till deposits are interspersed throughout this area. Surrounding the central region, streamlined and thick drift terrains dominate. In the southeast, both crosscutting streamlined landforms (palimpsest) and landforms with diverging orientations (relict) indicate preserved terrains related to older ice-flow directions. In the east-northeast, streamlined landforms overprint the southwest flow and suggest the late-deglacial Dubawnt Lake Ice Stream extended further west/northwest than previously mapped. A series of ice marginal glacial lakes, ice-contact glaciofluvial deposits and minor moraines record the retreat of the ice margin across the study area. The most prominent ice margin feature is a large N-S trending hummocky ice-contact glaciofluvial complex along the western border of the Thelon Game Sanctuary. This major ice retreat still-stand position is interpreted as a southwestern extension of the McAlpine Moraine System.

The variability in till composition is related to net glacial erosion and transport and provenance. Future till geochemical, indicator mineral and lithological analytical results will be used to evaluate glacial transport characteristics under shifting glacial dynamics and basal ice conditions over time. Geochronological samples were collected to constrain ice margin retreat history (absolute ice-free dates), and to test for degree of inheritance/glacial erosion (relative age dates). This work is intended to improve the geoscience framework for mineral exploration. This GEM-2 project is a collaboration between the Geological Survey of Canada, the Northwest Territories Geological Survey and Canada-Nunavut Geoscience Office.