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Under Cormorant Hill

June 5, 2009

 

Geological field party eating lunch on the shore of Cormorant Lake (June, 2006)

Geological field party eating lunch on the shore of Cormorant Lake (June, 2006)

 

 

I am spending a couple of days at Cormorant Lake in northeast Manitoba, looking at the Ordovician – Silurian boundary with Bob Elias of the University of Manitoba and our student, Matt.

Cormorant is a beautiful place, almost the end of the (dirt) road. When you get there, there is not a lot of “there there,” if you are looking for the busy human world. But the peaceful natural world more than compensates for this.

 

The famed Hudson Bay Railway passes through Cormorant.

The famed Hudson Bay Railway passes through Cormorant.

 

Saxifrages on the shore of Cormorant Lake in June, 2006. This year the weather has been much colder, and the flowers are not yet in bloom.

Saxifrages on the shore of Cormorant Lake in June, 2006. This year the weather has been much colder, and the flowers are not yet in bloom.

The modern veneer is a landscape of boreal spruce and aspen forest, with low hills and wide clear lakes. Hidden not far beneath the surface of Cormorant Hill is a very different ancient place. Here, layer upon layer of dolostone bedrock tells us the story of tropical environments that changed as the Ordovician world disappeared while giving birth to its Silurian successor.

It was not an easy birth. All the rocks we are looking at were deposited on the floors of salt seas. In older Ordovician rocks in Manitoba, we find amazing fossils such as the giant trilobite and abundant corals at Churchill. But here at Cormorant, the Ordovician rocks are almost devoid of fossils, and features such as salt crystal lattices suggest a hot, dry, and hostile place.

 

This is a vertical quarry face near Cormorant. The yellow arrow indicates the contact between the Ordovician Stony Mountain Formation (below) and the Stonewall Formation. This is a very irregular surface which is indented by channel-like features. It suggests a period during which sediment was not being deposited, and the surface may have been above sea level for a while.

This is a vertical quarry face near Cormorant. The yellow arrow indicates the contact between the Ordovician Stony Mountain Formation (below) and the Stonewall Formation. This is a very irregular surface which is indented by channel-like features. It suggests a period during which sediment was not being deposited, and the surface may have been above sea level for a while.

 

These Silurian corals are from the Fisher Branch Formation near Cormorant. An overturned horn coral (solitary rugose coral) is on the left, with a favositid tabulate to its right. The coin is 23 mm across.

These Silurian corals are from the Fisher Branch Formation near Cormorant. An overturned horn coral (solitary rugose coral) is on the left, with a favositid tabulate to its right. The coin is 23 mm across.

After the Ordovician gave way to the Silurian, conditions here were still far from pleasant: a hot, muddy, almost lifeless place. But then things improved, as they always will given time. As we got higher into Silurian rocks this afternoon, we reached a formation where fossils are quite common. It was very pleasing to spend the latter part of the afternoon finding nice specimens of a variety of corals and brachiopods (lamp shells).

Our perspective also improved, and it was cheered immensely by the numbers of red squirrels who kept visiting us, popping up out of the crevices in the rocks. Though, as I said to Matt and Bob, the behaviour of the squirrels, jumping attentively onto boulders very close to us, was disconcertingly similar to that of the group of cute little Compsognathus in one of those Jurassic Park movies.

 

Moss on a quarry floor near Cormorant

Moss on a quarry floor near Cormorant

On the way back to The Pas, we stopped to check another quarry, and got out to take a look at the pair of ospreys nesting at the top of a pole beside the Hudson Bay Railway. The ospreys, of course, took note of our presence and commented on it with a high pitched “craawk craaawk craaawk craaawk …”

 

The power line had been re-routed around the osprey nest.

The power line had been re-routed around the osprey nest.

Short conversation between two paleontologists:

“They make sort of wimpy sounds for such big birds.”

“Do you plan to go down there and tell them that?”

“Hmmm. Not really.”

 

A cliff face beside Clearwater Lake

A cliff face beside Clearwater Lake

 

Snow can still be seen in the deep crevices beside Clearwater Lake.

Snow can still be seen in the deep crevices beside Clearwater Lake.

 

aspen

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