North Shore Lake Superior, Ontario

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay

TB = Thunder Bay; BB = Black Bay; NB = Nipigon Bay. The Slate Islands are a probable meteor impact structure.

K: Cretaceous rocks of the Hudson Bay Basin
D: Devonian rocks of the Hudson Bay Basin
S: Silurian rocks of the Hudson Bay Basin
O: Ordovician rocks of the Hudson Bay Basin
Ya: Precambrian Y alkaline intrusive rocks
Ys: Precambrian Y sedimentary rocks of the Sibley Group
Yi: Precambrian Y intrusive rocks
Yv: Precambrian Y volcanic rocks, predominately basalt
X: Precambrian X metasedimentary rocks (not shown separately except on east shore of Thunder Bay)
Wgn Precambrian W (Archean) rocks, mostly gneiss with granite
Wg: Precambrian W granite with other rocks
Wa: Precambrian W syenite and other alkaline rocks
Wq: Precambrian W two-mica granites and other anatectic rocks
Wv: Precambrian W metavolcanic rocks, mostly mafic
Wf: Precambrian W felsic metavolcanic rocks

Thunder Bay

The topography around Thunder Bay is rugged with numerous mesa-like hills. The steep bluffs are Keeweenawan mafic sills and the intervening rocks are mostly Proterozoic metasedimentary rocks.
Mount McKay dominates the south side of the city of Thunder Bay and offers a wonderful scenic view
Thunder Bay Visitor Center
Looking across Thunder Bay to the Sibley Peninsula. The ridge is nicknamed "the sleeping giant."
The city of Thunder Bay was formed in 1970 by joining the twin cities of Fort William on the south and Port Arthur on the north.
Looking southwest. The distant hills are two islands: Pie Island on the left and Flatland Island on the right.
Looking south toward Mount McKay.
A road leads halfway up Mount McKay and trails lead to the summit. This is the city of Thunder Bay as seen from the end of the road.
Left and below: views of the Sleeping Giant.
Looking south. Pie Island is the large island, Flatland Island is the small one. Both owe their mesa-like appearance to Keeweenawan sills. On the distant horizon behind them is Isle Royale.
Beach ridge on the flank of Mount McKay, relic of a glacial high stand of ancestral Lake Superior.
View of Mount McKay from the base.
The Terry Fox Overlook is just northeast of Thunder Bay
View of the city and the Sleeping Giant from the overlook.
Close up of the monument. The text is below.

Terry Fox was a cancer victim who tried to run across Canada, despite having a prosthetic leg, to raise money for cancer research. This was a huge news event in Canada.

Text on the Terry Fox Monument

Dreams are made if people only try
I believe in Miracles. I have to...because somewhere the hurting must stop.

July 28, 1958 - June 28, 1981

Terry Fox inspired this nation with his dream - his marathon of hope - a cross-Canada run to raise money for cancer research.

This courageous young man from Port Coquitlam, British Columbia, knew only too well the ravages of cancer... because at 18 he had lost his right leg to the disease, and etched in his mind was the pain and suffering on the faces of other cancer victims. Determined not to leave "this world of miracles" before a cure had been found, he planned his 5,300-mile marathon.

After dipping his foot in the Atlantic, he began his epic in St. John's, Newfoundland on April 12, 1980.

Running 26 miles a day, this outstanding young athlete had conquered five provinces by the time he had reached Ontario in June. Then, at mile number 3,339, near this very site, recurring cancer forced him to give up his run.

"It feels good to give," he told the people of Ontario who responded wholeheartedly to his courage and his dream, and through his perseverance in the face of overwhelming odds, he inspired an outpouring of immense national pride and a flood of $24 million for cancer research.

To the people of Ontario, Terry gave us pride - pride in having known him and, briefly, sharing his dream.

To every Canadian, he left us his challenge - a challenge each of us will meet in our own way.

[Since 1981, foundations started by or dedicated to Fox have raised hundreds of millions of dollars for research.]

The Sibley Group

The Sibley Group consists of mid-Proterozoic red beds, younger than the Precambrian X rocks of Minnesota and Huronian Supergroup, but older than the sedimentary rocks associated with the Mid-Continent Rift System. And when I say red, I mean red. They are exposed in many localities around Black and Nipigon Bays.
Left and below are closeups of the red sedimentary breccias.

Amethyst Mine

There are lots of small amethyst mines north of Thunder Bay. I picked one at random and headed up a dirt road.
The workings.
The granitic rocks are very red (no mystery where the Sibley Group gets its color) and have lots of quartz veins.
Here we see where an amethyst vein was dug out.
A small amethyst-lined cavity.
A quartz vein with an amethyst core.
Left: differential weathering of aplite and granite.

Below: A small mafic intrusion showing a baked contact in the granite.

Lake Nipigon Highway

Highway 11, the north branch of the Trans-Canada Highway,  branches off from Highway 17 (the main branch) at Lake Helen, about 100 kilometers northeast of Thunder Bay.
For about 10-15 kilometers the road follows the shore of Lake Helen. Lake Helen links the Nipigon River with Lake Superior.
The road follows a steep sided valley for much of the way, with dramatic scenery. The rock is entirely Keweenawan mafic sills.
Waterfalls are numerous on the way.
Meter-scale columnar jointing in the mafic intrusives.
The only place any of Lake Nipigon is visible from Highway 11 is Rocky Bay, about 50 kilometers north of Lake Helen.

Lake Nipigon

80 kilometers north of Lake Helen, secondary road 580 heads west 12 kilometers to the shore of the lake. This is the only easy access to the main body of the lake.

Why Lake Nipigon is not considered part of the Great Lakes has always mystified me. True, at 1872 square miles, it's only a quarter as large as Lake Ontario, but it's still a very big lake.

Nipigon Bay

Nipigon Bay on Lake Superior exhibits some of the most spectacular shoreline scenery on the drive. The mainland rocks are mostly Archean crystalline rocks but the offshore islands are mesas formed by Keweenawan sills.


Left and below: scenery near Marathon.
A nifty orographic cloud. After a whole day of nice weather, the only low stratus cloud I saw all day was this one where the wind off the lake met the hills. After blowing across 300 miles of lake, the air had picked up a lot of moisture.

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Created 24 May 2006, Last Update 06 June 2020