CASS CITY, MI -- More than 100 petroglyphs are being digitally scanned and recorded as part of a archaeological project to preserve the 'glyphs on the Cass River floodplain.

The petroglyphs are located in the 240-acre Sanilac Petroglyphs Historic State Park at 8251 Germania Road in Cass City.

"(The glyphs) were carved over a long span of time," said Dean Anderson, state archaeologist for the state of Michigan. "Probably the most identifiable and the most well-known is the individual with the bow and arrow."

He said some of the drawings could go as far back as 1,200 to 1,400 years because the bow and arrow were first presented as technology across the Great Lakes region around then.

The petroglyphs site was vandalized last year by someone drawing a cat and mushrooms on it.

The Michigan Department of Transportation uses a special type of equipment called Light Ranging and Detection (LiDAR) and close-range photogrammetry-overlapping detailed photographs to build digital models of the petroglyphs that will help document the site and track its preservation, according to a news release.

The technology uses pulses of light to bounce off the surface and back into the machine.

Anderson said the technology is very precise and the accuracy is on a "submilimeter" level.

"People worldwide have carved images into stone to honor their ancestors, record teachings and mark important events," said Stacy Tchorzynski, an archaeologist with the State Historic Preservation Office and project manager for the Sanilac Petroglyphs, in a news release. "Sanilac Petroglyphs Historic State Park has Michigan's largest known collections of carvings, which likely date from within the last 1,400 years."

She also said the project is partnered with the State Historic Preservation Office, MDOT and the Ziibiwing Center of Anishinabe Cultures and Lifeways, Saginaw Chippewa Indian Tribe of Michigan, Department of Natural Resources and Michigan History Center.

"it is an archaeological site, it's important to us for those reasons, we are interested in helping the public see the site to be exposed to those different points of view," Anderson said.

Tribal officials could not be reached for comment.

While the petroglyph area is closed for the year, admission is free to enter the park and it's open from May to September, from Wednesday through Saturday, and the one-mile hiking trail and park is open year round.