Feature Article November 13, 2002
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Sunbury Shores a Special PlaceNear Sunbury there is a really special place where there are tracks from one of the earliest ever ventures of animals from the oceans onto the land. The tracks are ribbon-like trails, 3 to 4 inches wide, in sandstone. The animals that made these tracks were ancient arthropods about a foot long -- giant ancestors of our insects and other existing arthropods like centipedes and millipedes.
Rainer Wolf, a graduate student working with Professor Bob Dalrymple in the Queens University Department of Geology, discovered the tracks in 1983. Bob Dalrymple and other geologists have concluded that these animals were walking in dry sand dunes, not on the ocean floor at a time when life on land was very rare. Plant life on land was probably restricted to only some algae, fungi and lichens. Evidence for animals at that time was almost entirely from in the oceans -- not on land.
Based on the age of the rocks where the tracks are found and knowledge of the geological history of the area, Professor Dalrymple estimates that these animals walked on this sand dune about 498 million years ago. That means that these animals were coming onto land in the late part of the Cambrian. Before the discovery and analysis of these tracks it was believed that animals did not appear on land until about the end of the Ordovician, only about 450 million years ago.
Thanks to the good fortune that these tracks were preserved in Potsdam sandstone, one of the most indestructible rocks, we have this evidence of the earth's history. From this evidence, Rainer Wolf, Bob Dalrymple and their geological colleagues have produced another bit of new knowledge* for us from one of the special places where we live.
Interested in Canadian fossils and what they tell us? Try "Eight Small Steps" by Wayne Grady of Athens in Canadian Geographic, Nov/Dec 2002 and www.fossiltrail.org.
