Geology of Lake Nipigon

From Great Lakes Wiki

Remote sensing imagery of Lake Nipigon. See the actual imagery at the Natural Resources Canada

The most interesting geologic feature of Lake Nipigon is green-black sand beaches. These result from a molten rock that came up through cracks in the earth’s crust some one billion years ago. This rock, diabase, contained pyroxene, a dark green mineral. This rock has since weathered and left a green-black sand to settle in the area and continually wash on shore. Another oddity of the landscape is the tall cliffs, some of which tower 170 meters above the countryside and provide breathtaking views.

Underlain in the area is ancient rock from the Neoarchean (2800- 2500 million years ago) to the Mesoproterozoic (1600-1000 m.y.a.) eras. Overlaying this bedrock there is Quaternary (1.8-1.6 m.y.a.) deposits.

The basin is part of the Canadian Shield. This can be seen by the angular lakes surrounding Lake Nipigon. These lineaments suggest that the crust of the area was under intense pressure hundreds of millions of years ago and broke instead of bending as they normally would. This allows erosion to carry the fragmented rock away leaving the fault area that was quickly filled with water. The lakes are angled due to pressure that stressed and only bent them in the geological past.

There are also striations in the landscape resulting from recent periods of glaciations. These elongated features include drumlins, which are elongated mounds of glacial sediments known as till, and elongated scours which invite water to accumulate forming lakes, swamps and marshes.

To the northwest of Lake Nipigon are a series of lakes with a peculiar shape. These lakes are on top of very dense, solid rock that will not allow water to drain through. There are larger lakes in the valleys between the hills and also small ones atop the hills. The lakes resting on top of the hills are isolated and their only source of water is rain and snow melt.

Amethyst is often found in the Lake Nipigon area. Due to its prominence in the area it was named Ontario’s provincial gemstone in 1975. The crystal has a six sided point formed from crystallized silica compound that lays interspersed between rocks. Local artists have taken advantage of its abundance and fashion jewelry from the stone. Shops selling their work are common from the Thunder Bay area to Lake Nipigon.

In 1955 the Institute on Lake Superior Geology was formed. They stat that their mission is to, “Provide a means whereby geologists in the Great Lakes region may exchange ideas and scientific data; to promote better understanding of the geology of the Lake Superior region, and to plan and conduct geological field trips.” In 2005 their annual conference was held in Nipigon Ontario and jointly attended by members of the Ontario Geological Survey and Lakehead University.

They have announced the two-year Lake Nipigon Region Geoscience Initiative hoping to involve members from the field to conduct geological, geochemical and geophysical surveys. This Initiative hopes to gain an understanding of the Lake Nipigon basin.