While no one is going to find any dinosaur bones in the Rock Glen Gorge, they will find hundreds of equally ancient creatures. Located in the Rock Glen Conservation Area, the gorge was created by the relentless erosion of the Ausable River into layers of limestone and shale.
As the ancestors of today’s shellfish died they drifted to the bottom of an early ocean, where they hardened into rock. Above them, more layers were deposited, and they also hardened. When the last glaciers finally melted, the water of today’s Ausable River eroded into the soil and then into bedrock to gradually expose the former seabeds and their trove of early critters.
Fossils appear in much of Ontario’s bedrock, and most usually require a pick to remove. But what makes the fossils in the damp little gully so unusual is that, during rainfalls, the shale turns soft enough to allow the shells to be removed by hand. The most common fossils found here are the branch-like staghorn coral or plant-like crinoids. Less common are the snail-like trilobites. The most interesting are the butterfly-shaped brachiopods, which the Chinese call "stone butterflies."
While the fossils can be found throughout the little valley, the footing is tricky. The hunting grounds lie deep in the 25-metre chasm, where the stream trickles around boulders.
Rock Glen Conservation Authority has a few rules. Picks and shovels are not permitted, nor is collecting from the valley walls themselves. Loose sediments, however, are everywhere, and here you can help yourself.
The park has a museum and staff with helpful brochures. The 25-hectare conservation area is on Lambton County Road 12, close to the village of Arkona, in south-western Ontario.
— Used with permission from Top 125 Unusual Things to See in Ontario, 4th Edition, Revised & Expanded by Ron Brown (Firefly Books, August 2014, $24.95).