[1] The region was covered by the massive Laurentide Ice Sheet, which retreated almost 12,500 years ago and made way for the Champlain Sea.

As the land rose due to post-glacial rebound the sea retreated and the Saint Lawrence River developed about 9.500 years ago.

The land covered by the Tourbière de Shannon was in the Jacques-Cartier River delta on the border between the Laurentian Mountains and the Champlain Sea, and is dominated by thick sandy glaciofluvial deposits.

[1] The Tourbière de Shannon holds over 1,000 individuals of the eastern prairie fringed orchid (Platanthera blephariglottis), growing near groves of larch and black spruce in open and semi-open areas.

There are also over 500 individuals of the southern twayblade (Listera australis) in areas where trees and shrubs give good protection, often on the south side of groves.