Nonacho Bedrock Mapping Project

Nonacho Bedrock Mapping Project

Conglomerate belonging to the Nonacho Group.


The Nonacho bedrock mapping project aims to provide better geoscience knowledge for a poorly known area of the southeastern Northwest Territories. The area is underlain by sedimentary rocks that were deposited on old Archean basement rocks. The basement rocks were last mapped by geologists in the 1950s and 1960s, and the sedimentary rocks in the early 1980s. The Northwest Territories Geological Survey (NTGS) is mapping the bedrock geology and collecting samples for analysis. University partners are investigating the timing of sediment deposition and metamorphism. Together we are unravelling the geological history of the area and beginning to assess its mineral potential.

The Nonacho study area is located southeast of Great Slave Lake in the Rae Craton of the Canadian Shield.


The project area is in the southeastern part of the Northwest Territories between the East Arm of Great Slave Lake and Saskatchewan. The area of interest is around Nonacho Lake - National Topographic System (NTS) 75F, and includes part of the Akaitcho region. The geological area of interest is the Rae Craton, which is part of the Canadian Shield.

Geologists often use a helicopter to map the geology in remote areas of the Northwest Territories.


Very little research has been conducted in this remote area, and our current geological knowledge is poor. It is estimated that 80% of the Canadian Shield in the southeastern NWT is not mapped well enough to support informed land-use decisions. A systematic approach to mapping the land is needed to provide good baseline data on the underlying geology. Such data is necessary to assess the geological history of the area and its economic potential.

A chisel and hammer are used to remove a small rock sample to be sent to the lab for analysis.


Geological bedrock mapping is being conducted by a team of 5 to 7 geologists, including government staff, summer students, and university professors and graduate students. The geologists work from a small camp that is moved weekly and boats are used to access shoreline outcrops. Samples of fist-sized rocks are collected for laboratory analyses. The field observations are compiled and interpreted after each field season and integrated into a geology map. The results of analyses add to our understanding of the geological processes that form the land we walk on today. The results of our work are published in the form of geological maps and scientific reports that can be downloaded by anyone who is interested.

The geology is often revealed at bedrock exposures along lake shorelines.  Geologists map the shoreline geology using a zodiac.


The project begins in 2018 with field work by Northwest Territory Geological Survey (NTGS) researchers and university partners. The field work consists of 3 weeks of mapping and sampling in the Nonacho Lake area - National Topographic System (NTS) 75F. Mapping is anticipated to continue in summers 2019 and 2020. Final results of the research will be published as downloadable NTGS reports.

A geologist measures the orientation of sedimentary rocks on a shoreline outcrop east of the Nonacho project area.

Partners and Support

Larry Heaman and Thomas Chacko
University of Alberta

Alessandro Ielpi (2019)
Laurentian University

The pseudotachylite in the centre of this photo formed under high pressure associated with rapid movement along a fault zone.


Nonacho Group, Nonacho Lake, Rae Craton, Churchill Province, tectonic, bedrock mapping, geology map, sedimentary basin, Proterozoic, Archean, Taltson Orogeny, Trans-Hudson Orogeny, uranium mineralization