Scientists just uncovered three ancient worlds frozen beneath Illinois for 300 million years

Over 300 million years ago, Illinois teemed with life in tropical swamps and seas, now preserved at the famous Mazon Creek fossil site. Researchers from the University of Missouri and geologist Gordon Baird have reexamined a vast fossil collection, uncovering three distinct ancient environments—freshwater, transitional marine, and offshore—each with unique animal life. Their findings, enhanced by advanced imaging and data analysis, reveal how sea-level changes, sediment conditions, and microbial activity shaped fossil formation.