Still Waters

This is a very deep lake (22.5 metres), considering its relatively small surface area (you can walk around it in about half an hour). It is called a meromictic lake, meaning that the deeper levels of water are indeed very still - they do not mix with the water closer to the surface, an unusual situation in lakes. Although water flows into the lake, and rain falls into it, this water from the environment doesn't sink down to the bottom. One of the results is that there is no oxygen in the deepest water to cause chemical changes in organic matter that does reach the lake floor.

This means that sediments that are in the lake have remained there unchanged for hundreds of years.

The conservation area which manages this lake doesn't allow swimming, fishing or boating, so that the lake continues to be undisturbed.

Archeologists have been able to take samples of sediments from the lake bed and analyze and date them, to find that there are grains of pollen from corn which was cultivated by the Iroquoian people, as early as 1000 AD.

References:
Wikipedia
Ontario Ministry of Natural Resources
Meromicitc Lakes
Processes of a Meromictic Lake
Conservation Halton
Archeological Research in the Crawford Lake Area