Fossil hunting at Macoun Marsh

by Richard Singhroy

Richard Singhroy is a student at the University of Ottawa. As part of the university’s Community Service Learning program, he has volunteered to report on several OFNC outings and meetings. On November 7, he joined the Geology Interest Group to look for fossils.

Coral fossils spotted at Macoun Marsh

Coral fossils spotted at Macoun Marsh (click for larger image)

Now, it wasn’t digging for dinosaurs, but something equally interesting.

First a bit about Macoun Marsh. It is a small patch of trees near a tiny stream next to Beechwood Cemetery – a truly a beautiful place. The rocks that were brought to the marsh were quarried at Labreton flats next to the Ottawa River.

These limestone rocks are 458 million years old. They were formed during the upper Ordovician period. To give you some context, during this period, our area was almost entirely ocean, and most of the world’s land was a supercontinent known as Gondwana. Throughout the Ordovician period, Gondwana shifted toward the South Pole and much of it was submerged underwater. The Ordovician is best known for its diverse marine invertebrates, including graptolites, trilobites, brachiopods, and the conodonts.

Now for the good part. What did we find? Well, brachiopods were the first thing. Brachiopods are a phylum of small marine shellfish, sometimes called lampshells. They are not common today, but in the Palaeozoic period they were one of the most common types. They lived near the shore (littoral zone), but now they have been pushed into deeper water by competition from bivalve molluscs. Like mussels they have shells, but the shells do differ.

Sponge fossil found at Macoun Marsh

Sponge fossil found at Macoun Marsh (click for larger image)

We also found sponges and coral fossils (see photos). These are more widely known than brachiopods.

Next we found an orthocone. An orthocone is a long straight shell of a nautiloid cephalopod. During the 18th and 19th centuries, all shells of this type were named Orthoceras, but it is now known that many groups of nautiloids developed or retained this type of shell. An orthocone is like a nautilus shell, but straight and uncoiled. It was previously believed that these represented the most primitive form of nautiloid, but it is now known that the earliest nautiloids had shells that were slightly curved.

I found the last to be the most interesting. Trace fossils are literally what you think they might be, a fossil that an animal left behind, like a footprint. I’m amazed how a path left behind millions of years ago can still be seen today.

I really enjoyed my morning and learning the geology of the distant past. The setting was nice and the fossils were very intresting. I would definitely recommend that you visit Macoun Marsh if you get a chance.

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