Paleontology and geology
The Precambrian: Most of the bedrock in Manitoba is Precambrian in age and belongs to the Canadian Shield, the core of the North American continent. These igneous, sedimentary, and metamorphic rocks record ancient oceans, islands, volcanoes, and continents that existed from 2.8-1.1 Ga. They are divided into two geologic provinces based on their shared histories: the Superior Province in the southeast and the Churchill Province in the northwest. Rocks from both provinces are mined for their economically important deposits.
The Paleozoic: In the Paleozoic, two basins developed to the southwest and northeast of Manitoba, which allowed shallow seas to encroach on the province from time to time. The stromatoporoid and coral reefs that developed in the warm, tropical waters were home to many different invertebrates, including brachiopods, mollusks, and arthropods. As the seas retreated, they became so shallow that the water evaporated, leaving deposits of salt and gypsum. When Manitoba was above sea level, erosion was the dominant force shaping the landscape, and many Paleozoic rocks have been removed or buried.
The Mesozoic: Most of Manitoba was above sea level and exposed to erosion during the Mesozoic. Deposition was restricted to lakes, river valleys, and lowlands. In the southwest, a few continental deposits from the Jurassic remain, as well as beach and lagoon deposits from the short-lived Jurassic seas. In the Cretaceous, the Western Interior Seaway spread across southwestern Manitoba, and the warm water was home to many invertebrates, such as foraminifera, bivalves, crustaceans, and cephalopods. A great variety of vertebrates could also be found here, including sharks and other fish, marine turtles, plesiosaurs, mosasaurs, crocodiles, and early birds.
The Cenozoic: After the Western Interior Seaway withdrew in the Early Cenozoic, southwestern Manitoba was covered by a huge swamp, and the plants that lived here have been turned into coal. Many of the Tertiary deposits have either been removed by erosion or buried by sediments from the many glaciers that spread over Manitoba in the Quaternary. After the last glaciation, a large lake covered most of the province, while the tundra and forests around it were home to Ice Age giants.