undifferentiated rock units

Paleontology and geology

During the Early and Middle Cambrian, Manitoba remained above sea level and exposed to erosion. But by the Late Cambrian, a basin began to form to the southwest, and the warm, tropical seas encroached on the southwestern corner of the province. Sediments eroding off the highlands were deposited in the basin and along the shore of this sea, forming sandstones and mudstones. These shallow marine deposits contain fossils of brachiopods and trilobites, but most of these rocks are buried below the surface under younger deposits. A few exposures may appear on more detailed maps.