Petroglyphs of Southern Illinois and Southeastern Missouri	by Mike Chervinko
Central States Archaeological Societies 2024 April Journal	Carbondale, Illinois

A bird barely poking out of the Mississippi River.

When we think of petroglyphs in the United States, what commonly comes to mind are arid landscapes out west full of carving-filled cliffs and boulders.In truth, there are petroglyphs in all 50 states – as well as just about every country on the globe. It is thought southern Illinois and southeastern Missouri host the second greatest density of petroglyph sites here in the United States, outside of the American Southwest. Between these two areas there are around 200 sites, with some spots containing over 100 images. When we stop to think about it, this makes sense given these areas were heavily populated prehistorically and have an abundance of exposed rock suitable for marking. Most images are thought to date to the Mississippian era, though plenty of images from Archaic and Woodland times are present as well. Moreover, several sites show evidence they were visited and marked on for thousands of years. This means a single site may have images ranging in time from the Archaic period through the Mississippian period. Dating sites can be very challenging, but a few clues that help include: artifacts found associated with sites, the motifs present and carbon dating. Cross referencing images with other artifacts is helpful too.

In simple terms, petroglyphs are carved or painted images on rock faces. There are a few methods those people used to create the images and they include pecking, scraping, and/or forming the image as a base relief. This third method is the rarest method seen by far. When an image is painted or drawn, it is known as a pictograph. Materials used to create pictographs include her paint, plant pigments, charcoal and/or using the charred end of sticks. Some images were both etched and painted. Ocher is a rust colored paint created by mixing crushed iron with animal fat and maybe a few other ingredients. The slurry that results can be used to produce durable images that can last thousands of years because the paint is able to penetrate the rock, forming a thick layer. Moreover, the iron in the paint is not reactive to the UV in sunlight, so the images technically never fade. Still, over hundreds or thousands of years mineralization, and the buildup of debris (accretion), can cause the paintings to appear faded. Because these paints contain organic compounds they can be carbon dated when aging a particular site. If a site contains no pigments, it cannot be carbon dated. St Louis based archaeologist Dr Michael Fuller, has spent years scanning prehistoric paintings in Missouri using a pXRF machine in order to ascertain the pigments’ chemical makeup. More recently, he has been working with another archaeologist, Dr Karen Steelman, who has developed one of the most precise methods of carbon dating to date. Older methods are accurate to plus or minus 300 years, but her method, which uses plasma oxidation, yields a date range of only plus or minus 70 years! Moreover, her technique requires a much smaller sample compared to older dating methods, and is therefore less destructive to the paintings. With the help of Dr Steelman, his work is doing much to provide some of the most...

 

Read the complete "Petroglyphs of Southern Illinois and Southeastern Missouri" column in the Central States Archaeological Societies 2024 April Journal which can be purchased on-line after March 2025

Figure 2. This hand thought to be up to 5000 years old. The ring around it is a failed attempt to cut it from the rock