Mazon Creek fossil beds

Near Morris in northern Illinois, the Mazon Creek fossil beds preserve an unusually detailed record of life from about 309 million years ago, when this part of North America lay near the equator in a tropical setting. Fossils formed in the Francis Creek Shale as plants and animals were quickly buried and enclosed in siderite concretions, preserving soft tissues as well as hard parts. The site is especially important because it captures both coastal and inland communities, revealing a broad ancient ecosystem rather than a single habitat. Its rich Carboniferous flora and fauna include more than 400 plant species, more than 320 animal species, and the famous Tully Monster.

Carbon Hill, Illinois · United States