undifferentiated rock units

Paleontology and geology

In Northwest Territories, Precambrian rocks are exposed at the surface over the eastern half of the territory and form the basement below younger rocks. They record multiple continental collisions and breakups, and represent many different islands, oceans, volcanoes, and continents. They have been divided into three geologic provinces based on their shared histories: Rae (Churchill) Province, Slave Province, and Bear Province. The Slave Province contains the 4.03 Ga gneisses that are the oldest rocks in the territory, as well as some of the oldest stromatolites. After all these pieces came together to form the early North American continent, they were surrounded by shallow seas, which were home to various Ediacaran-type animals. Fossils of disc-shaped Ediacaria, tentacled Hiemelora, and segmented Windermeria, among others, are found in shallow marine sandstones. Some of these rocks are layered between conglomerates deposited by ancient glaciers. These rocks are now exposed in the southwest after being pushed up by later mountain-building episodes.