undifferentiated rock units

Paleontology and geology

In the Early Ordovician, a small area in northeastern British Columbia was exposed above sea level, while most of the province was part of the continental shelf and covered by shallow water. By the Middle Ordovician, the seas spread over the northeast as well. The continental slope and ocean basin were located where the western part of the province is today. Sandstones, shales, and limestones accumulated in these warm, tropical waters. These rocks preserve a snapshot of life in Ordovician seas. Sponges, corals, stromatoporoids, and receptaculitids built up reefs that were home to brachiopods, gastropods, trilobites, cephalopods, graptolites, and conodonts. Fossils of these animals can be found in some Ordovician rocks exposed in the north. The exposures are too small to show on this map, but they may appear in the undifferentiated rocks here or on other more detailed maps.