I didn't know what a petroform was before last weekend when we took a short hike in the Whiteshell to visit Bannock Point. There on the natural stone outcrops you will find rocks placed with intention in shapes of animal, man, and unknown formations. The information on the site was limited and our guide didn't show up as expected, so we took a long walk to explore the area. It was quite peaceful, besides my constant fear that the kids were going to kick or pick up a sacred rock.
Here's some quick information about petroforms, and below that, information about Bannock Point petroforms.
"Petroforms are shapes and geometrical patterns made from arranging large rocks and boulders, often over large areas of open ground, unlike the smaller petroglyphs and graphs which are inscribed on rock surfaces. They were originally made in North America by native peoples for astronomical, religious, sacred, healing, mnemonic devices, and teaching purposes. The specific names of these rock formations and the uses varied by political and religious group. Presently, some of these sites are still being used by First Nations, elders, and others." - Wikipedia
"Exactly who made the (Bannock Point) petroforms is a question that cannot be answered. If some petroforms date to A.D. 500 as archaeologists have estimated, it will be impossible to determine who built them in terms of historical Native groups. Today the nearest Native groups are Anishinabe and they use the sites, but the Anishinabe do not claim to have the only valid interpretation of the meaning of the petroforms." - Parks and Natural Areas Gov. MB