While minerals are the core of most of our collections – colors, crystal forms, rarity? – fossils can be just as fascinating in form and rarity, though rarely colorful. For these reasons some of our members are devoted to fossils and their histories.

Happily these parts of southern Ontario are rich in the preserved remains of (usually) extinct creatures. There is a vast literature on the searching; classification and history of fossils and readers are encouraged to seek these out at libraries and shops.

Geological specialists called stratigraphers rely very heavily on fossils as they try to match (correlate) formations of rocks in one area with those in another, often hundreds of kilometres – or even continents – away. So, far from being objects of mystery and superstition to the ancients, today fossils are essential to revealing the relative ages of rocks. Of course this method is now backed up by the more precise radiometric technique.

The relative dating system, being all early geologists had, was first put to formal use in the superb work of William Smith’s map of 1815, finally published after years of observing rock layers (strata) as he built canals. This, after all, was the time of the great Industrial Revolution when coal was king and steam began to frighten horses (and people too!).

This was the time too when that great concept, the geological time scale, was being hammered out – bitterly at times. Now it is not only useful but essential for putting time and fossils into perspective. Collectors take note!

In these parts of Ontario (Toronto-Brampton-Niagara) we live on the eastern edge of a grand "saucer" tilted to the southwest on a great thickness of Ordovician carbonate rocks (limestone and dolomite) shale and sandstone. Farther west on the Escarpment are stacked rocks of Silurian age (See? You do need the time chart!). The top of the Ordovician, by the way, is marked by a brick-red (sometimes green-mottled) shale named Queenston Shale – a superb "marker" bed but with no visible fossils.

Still farther west e.g. London, are still younger Devonian beds (Sarnia’s oilfields) and farther, some Lower Carboniferous (Mississippian) rocks. So the great span of time represented here is happy hunting for collectors with rock ages from 440 m.y. to 260 m.y.

To get started herewith is a skeleton list (pun intended) useful in road cuts, stream valleys and on shores. Write to your editor for more details:

Ordovician and Silurian – graptolites (in black shales), trilobites, crinoids, cephalopods (long cones, some coiled), gastropods (snails), pelecypods (clams), brachiopods (like clams but oddballs).

Devonian – gastropods, pelecypods, brachiopods, corals (solitary horn shaped and colonial honeycomb and chain types).

But bear in mind. The time divisions are man-made. These ancient creatures weren’t smart enough to oblige and often "slopped over" from one age to the next. Well, who’s to quibble over a few million years?