Mountains graphic with white diamonds on itGeoscience and Exploration

Insights from bedrock mapping in the Mackenzie region, GEM program, 2009 to 2018

Thursday, November 21, 2019 - 8:20am to 8:40am Theatre One


K.M. Fallas (Presenting)
Geological Survey of Canada
R.B. MacNaughton
Geological Survey of Canada

Up-to-date bedrock geology maps are an important tool for exploration and for assessing geological hazards or geotechnical issues. In the early 2000’s, bedrock maps for a large region from the Mackenzie Mountains to the Franklin Mountains and Colville hills were based on reconnaissance work from the late 1960’s. These maps incorporated some generalized or informal stratigraphic terminology, and were available only as hardcopy prints or images of the hardcopy versions. To bring these maps up to date with GIS techniques, bedrock mapping activities were conducted by the GSC from 2009 to 2018 as part of the Geo-mapping for Energy and Minerals (GEM) program. During that time, an area covering more than 91,000 km2 was updated. By building on historical field observations and incorporating improvements to stratigraphic units from government and academic work over the last 50 years, GEM program maps for the Mackenzie region have revealed new aspects of the geological relationships. These include updating the distribution of economically significant units, resolving problematic correlations, improving stratigraphic resolution and age control, identifying previously unrecognized structures, and adding new constraints to the timing of multiple deformation events.

Revisions to the identification of units are most significant in Tonian strata (Katherine and Little Dal groups), Ediacaran to lowermost Cambrian strata (upper Windermere Supergroup, Backbone Ranges Formation), lower to middle Cambrian strata, and Cretaceous strata. Updated Cretaceous unit terminology is significant for maps north and east of the Mackenzie Mountains whereas the older units mainly affect the map relationships within the Mackenzie Mountains. Extension of the known distribution of the Coates Lake Group into the Bonnet Plume Lake (NTS 106B) and Ramparts River (NTS 106G) map areas may be of interest to those studying the copper mineralization in these strata. Biostratigraphic work conducted as part of the GEM program has tightened age control, and has aided in unit identification and correlation for intervals in the Ediacaran, Cambrian, Devonian, and Cretaceous. Stratigraphic and thermochronological evidence constrains timing of Laramide contractional deformation within the Mackenzie and Franklin Mountains to mid-Cretaceous to Eocene. The combined stratigraphic refinements have facilitated mapping at a finer resolution, in turn leading to the recognition of additional extensional and contractional structures. Better age controls on units involved in early extensional faulting help constrain the timing of extension to events in latest Tonian, early Cryogenian, late Ediacaran, and early to middle Cambrian.

The recognition of additional faults requires a reassessment of subsurface relationships, connectivity of fluid pathways, and overall shortening across the Foreland Belt of the Cordillera. Based on stratigraphic revisions, correlations, and structural mapping in the northern Mackenzie Mountains, significant revisions to the geological relationships in the central Mackenzie Mountains (NTS map areas 95L, 95M, 105P, and eastern 105I) are likely required, and further study could reveal important aspects of the depositional history and pre-Laramide deformational events.