undifferentiated rock units

Paleontology and geology

In the Late Precambrian, all the continents were part of a supercontinent that began to break apart about 750 Ma. This rifting created the ancient North American continent, Laurentia, and eastern British Columbia was on its margin. Sediments eroding off the land were deposited in the seas that surrounded the continent and covered most of the province. The shallow marine deposits include sandstones, shales, and limestones, some of which contain stromatolites and a few rare fossils of some of the oldest multicellular animals (e.g., Cyclomedusa). Glaciers formed on land a few times, and after scraping up the surface, they carried debris down to the sea. When the ice melted, large boulders and conglomerates were left on top of the usual marine deposits. Although these rocks formed over western British Columbia, more recent collisions have folded, faulted, and pushed them to their present position in the Rocky Mountains. The igneous and metamorphic rocks that were part of the continental margin in the Precambrian date back to 2.4 Ga, and they are only found below the surface in the northeast.