Connecting people with nature in Ontario's Mississippi Valley

Stromatolites Unknown

Submited by Sheila Edwards
December 20th 2005

Stromatolites Unknown

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During September’s MVFN meeting, Jim Bendell mentioned the stromatolites near Champlain Bridge. Chris Hume and I were intrigued, so after getting an idea of where they were, off we went. Not really knowing what to look for all we saw were concentric circles, slightly mounded, split by fissures, with odd little tuffs of grass. Not nearly as entrancing as watching a Great Blue Heron or having frogs leaping away while paddling, or spotting a salamander in the glare of a flashlight. The day was nice, the surroundings calm, we didn’t get lost, the picnic went well – just not as earth shattering as it could have been.

Back to the drawing board. What were we looking at? Why were they so important? There are some things one can appreciate without much knowledge, like the butterfly greenhouses at Carleton, or seeing a Great Grey Owl; not so the stromatolites. These odd mounds turned out to be heavily eroded, extremely old fossils; in fact, the oldest type of fossil known.

They are not the tiny fossils found on the shores of Lake Ontario, but a whole connected area of fossils. They were created by communities of cyanobacteria (blue-green algae) and other microbes, when this area was covered by warm salt water. The calcite produced by the cyanobacteria and the normal sedimentation of minerals becomes trapped within the sticky cyanobacteria, which then settle and start to harden each night.

Over time, a solid mound is formed, with a new cyanobacteria colony growing on top. Mounds form on top of mounds, which eventually fossilize. Glaciations and other erosion mechanisms resulted in our stromatolites becoming relatively flat. Looking at the stromatolites one sees concentric circles, indicative of the cycle of colony growth and sedimentation. The pattern of the rocks is reflective of the tides and currents.

There are other, smaller, examples of stromatolites along the Carp River near Fitzroy, along the Ottawa River near Dunrobin Shores, and along the Jock River. Today living stromatolites can be seen off the west coast of Australia and in the Bahamas.

Only by seeing the stromatolites were we led to further study, and through further study we understood and thus appreciated what we saw. Some things one need only see to appreciate but the circular pattern of learning and seeing results in a richer experience; an increasing appreciation of nature.