THE ORDOVICIAN PERIOD IN SOUTHERN ONTARIO
The greater Metropolitan Toronto area has some ideal sites for fossil hunting, since the principal rocks most likely to contain fossils are the sedimentary variety. Limestone is better represented than shale or sandstone, but all of these sedimentary rocks are represented (although not all will contain fossils).
There are a few sites in south-western Ontario between the Niagara Escarpment and Lake Huron/Georgian Bay but, in general, I shall concentrate upon the region bounded on the west by the Niagara Escarpment, on the north by the Oak Ridges Moraine and on the south by the shores of Lake Ontario. The Niagara Escarpment defines itself, sometimes spectacularly, in a band from north of Tottenham through Caledon down to Hamilton and across to Niagara Falls. The Oak Ridges Moraine extends from the north of the Regional Municipality of Peel at the Niagara Escarpment, bisects the Regional Municipality of York through Oak Ridges, and divides the Regional Municipality of Durham just north of Oshawa. The lakeshore forms the "hypotenuse" of the triangular site described.
This triangle is reported to be the "world capital" of Ordovician fossils in the Pelecypod Class of Mollusks. They include clams, mussels, oysters and scallops, which may be discovered as either moulds or casts in the limestone rocks.
It is unlikely that fossil hunters will discover anything amongst the débris deposited by glaciers in the Oak Ridges formation. However, stratified layers of sedimentary deposits are often seen along river beds and up the banks. The same is true for some hills, bluffs and escarpments, but the hunter must exercise caution when climbing steep surfaces and loose rocks. Before you begin to collect on private property, it is important to obtain permission. It is also wise to wait for the spring thaw and flooded rivers to give way to warmer sunny days and exposed sections of limestone beds of rivers. Too much sun is also a hazard, as has been widely publicized in the 1990's; don't forget to protect your skin with a sun block rated 15 or better.
Although "fossil" comes from a Latin word meaning "dug up", very few Ordovician fossils require such activity. In fact, many may be simply picked up, and a few might require extraction from their surrounding limestone matrix. In the latter instance, you'll need protection from flying rock chips, particularly for your eyes, but sometimes for your hands as well.