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TitleGEM Mackenzie Project: Preliminary surficial geology map, Wecho River, NTS 85-O, NWT
AuthorMorse, P DORCID logo; Kerr, D E; Wolfe, S AORCID logo
Source43rd Annual Yellowknife Geoscience Forum - Program and Abstracts; Northwest Territories Geoscience Office, Yellowknife Geoscience Forum Abstracts Volume (2015), 2015. Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20150316
Meeting43rd Annual Yellowknife Geoscience Forum; Yellowknife; CA; November 24-26, 2015
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
AreaWecho River
Lat/Long WENS-116.0000 -114.0000 64.0000 63.0000
Subjectsgeneral geology; surficial geology/geomorphology; geological surveys; geological research; bedrock geology; tills; eskers; glaciolacustrine deposits; organic deposits; Mackenzie Valley Corridor; glacial Lake McConnell; Surficial geology
ProgramGEM2: Geo-mapping for Energy and Minerals Mackenzie Corridor, Shield to Selwyn
AbstractThe Geo-mapping for Energy and Minerals (GEM) program of Natural Resources Canada provides a foundation for sustainable economic development in the North, and the Mackenzie Corridor region of interest represents the largest unmapped (bedrock and surficial geology) area of Northwest Territories. The goal of predictive surficial geology mapping is to develop timely first-version regional maps, validated in selected areas and reviewed by geological experts, which reasonably depict the distribution of basic or generalized surficial sediments, filling major knowledge gaps for northern industry exploration and development purposes.
The Wecho River map (NTS 85-O) identifies surficial geology and associated landforms resulting from the last glaciation (Wisconsinan), and from inundation about 13 000 cal BP by glacial Lake McConnell at the margin of the retreating Laurentide Ice Sheet. With continued falling lake levels due to differential isostatic uplift, the lake first separated from the Great Bear basin, and remained in existence until about 9500 cal BP, when the basins of Great Slave and Athabasca lakes separated. The resulting ancestral Great Slave Lake continued to decline, towards its present elevation of 156 m asl, constrained by the Mackenzie River outlet at Fort Providence.
This preliminary map of surficial geology is based on remote predictive mapping (RPM), airphoto interpretation and fieldwork. The RPM methodology adopted for mapping NTS 85-O was based on the availability of remote sensing data and the authors¿ field experience of surficial materials and geology found in the region. The technique builds upon experience gained in previous surficial RPM activities in adjoining areas, 85-I, 85-J, 85-N, and 85-P. Preliminary results show that bedrock predominates in the land area throughout the map (69.7% of map area) and till veneer deposits become more prevalent in the northeast (12.6%). Undifferentiated till (1.1%) deposits, though limited in extent, are more common in the northwest. Glaciofluvial esker complexes generally form linear deposits trending southwest, and vary in extent (2.1%). Glaciolacustrine sediments (12.9%) are common in some lake and river drainage basin valleys up to 250 m elevation or more where they are fine-grained, whereas coarser-grained glaciolacustrine beaches and deltas occur as high as 330-350 m in the northeast, likely defining the eastern limit of glacial Lake McConnell. Remaining land area is comprised of wet organic deposits (1.5%) distributed throughout the map sheet. Results from 100 cross-validations using 75% randomly sampled data for training and the remaining 25% for validation indicate and average overall accuracy of the training areas of >97%. However, based upon comparison of mapping results with extensive field survey data, several glaciofluvial deposits were confused with bedrock. The final iteration of the map will involve some manual reclassification of the glaciofluvial class. Future work in 2016 will be the production of predictive surficial geology maps at 1:250,000 scale for NTS 85-O and NTS 85-K in the Canadian Geoscience Map (CGM) format.
Summary(Plain Language Summary, not published)
The surficial geology of Wecho River (NTS 85-O) was mapped as a part of the Geo-mapping for Energy and Minerals (GEM) program of Natural Resources Canada. The preliminary map, based on remote predictive mapping (RPM), airphoto interpretation and fieldwork, identifies surficial geology and associated landforms resulting from the last glaciation (Wisconsinan), and from inundation 13 000 cal BP by proglacial Lake McConnell through to modern Great Slave Lake as the shoreline receded due to crustal rebound. Bedrock dominates the landscape (69.7%), with till veneer (12.6%) to the northeast, glaciolacustrine sediments (12.9%) to the south and south west, and with glaciofluvial deposits (2.1), undifferentiated till (1.1), and organic deposits (1.5%) distributed throughout. The final iteration of the map will be production in 2016 of a predictive surficial geology map at 1:250,000 scale for NTS 85-O in the Canadian Geoscience Map (CGM) format.

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