Remember your classes on Plate Tectonics and Continental Drift. During the Ordovician Period (500 – 440 million years ago) continents were moving together, the dominant sediment was lime mud, which later formed limestone and dolomite. During the Silurian Period (405-440 million years ago), the northern continents were joined together into a supercontinent called Laurasia, while the southern continents united to form Gondwanaland. Most of North America was covered by warm shallow clear seas and most of the rock being deposited was limestone. North America was moving south and was now close to the equator.
450 million years later, those marine sediments are known as the Severn River Formation which runs from Manitoba to Quebec, under the Hudson Bay. This formation appears in Churchill along the shore line and tidal flats. You can find fossilized bivalves (left and right shells are the same size), brachiopods (upper and lower shells of different size), gastropods (single coiled shell), cephalopods (straight uncurled Nautilus), Sponges, Echinoderms (Crinoids – “Sea Lilly” living fossils), many different kinds of corals : 1) Rugose – now extinct, solitary forms (Horn Corals) or colonies. 2) Tabulate – colonial (Mound, Sheet, Chain, Branch). The most exciting find by far was the discovery of the World’s Largest Trilobite which now resides in the Museum of Man & Nature in Winnipeg. Trilobites are 3 lobed Arthropods that were commonly 3 – 10 cm in length, the precursor to modern day crabs. The Churchill Trilobite measured in at 70 cm, causing paleontologists to create a new species – no one had any idea that they could actually grow that big!
Check out our photo gallery under Fossils.