undifferentiated rock units

Paleontology and geology

In the Cretaceous, subduction off the coast continued to add pieces of oceanic crust and islands to the continent, resulting in substantial volcanism and uplift. By the Late Cretaceous, the westernmost pieces of the province were added to the continent. As the mountains were uplifted, they were eroded, shedding sediment out to the ocean in the west and the Western Interior Seaway to the east. The sandstones, mudstones, and shales that formed along the seaway in the east preserve a snapshot of life in this area. Molluscs, fish, amphibians, turtles, and crocodiles lived in the sea and nearby lagoons, lakes, and rivers. Dinosaurs, such as hadrosaurs, ankylosaurs, sauropods, and various carnivores, roamed the beaches, mudflats, and swamps, leaving their tracks in the sediments. Pollen, spores, and leaf fossils from the east and Vancouver Island record a warm, humid climate and the increasing dominance of flowering plants through the period. Marine deposits in the west, especially on Vancouver Island, preserve the animals living in the seas, such as foraminifera, ammonites, gastropods, bivalves, and crustacans, as well as large marine reptiles (mosasaurs and elasmosaurs) and ocean-going birds.