July 26 , 2016

by Hank Black

The footprints were made by small four-legged creatures in what is now Walker County more than 300 million years ago, long before man walked the Earth. Even dinosaurs were 85 million years in the future. The tracks came from fertile, tidal flats of sand and mud near a swampy tropical forest on the coast of an ancient inland sea. The discovery of these fossilized traces of ancient life was made in 1999 by Oneonta High School teacher Ashley Allen at a surface coal mine near Jasper. The find set in motion a sequence of events that led to the area’s preservation as one of the most important fossil sites in the world. How the Union Chapel Mine was saved from reclamation to become the Steven C. Minkin Paleozoic Footprint Site is told in a book, “Footprints in Stone: Fossil Traces of Coal Age Tetrapods,” published this month by the University of Alabama Press. “Footprints in Stone” is a story of exploration, discovery, detective work and persistence that will appeal to the general reader or the hardened rock hound, said Ron Buta, coauthor of the book with David Kopaska-Merkel. Buta is a professor of astronomy at the University of Alabama who has had a long-standing fascination with fossils. Kopaska-Merkel is a geologist and professional paleontologist with the Alabama Geological Survey in Tuscaloosa.

The fossilized footprints that fill the mine site near Jasper provide some of the earliest evidence of reptile life and of the interaction of reptiles with amphibians. Preserved in shale, the fossils are remarkable in their sheer volume and in the number of species they record. Thousands of the fossil trackways, as geologists term them, have been collected, catalogued and made available for public viewing online or in person. “In addition to footprints of ancient animals, the fossils show other signs of ancient life, including the undulating pattern of fish fins in shallow water as they swim through the tidal mud flats,” Buta said. “These wavy patterns provide some of the earliest indication of schooling behavior in fish.” The layers of slate exposed by the mining operation at the Minkin Site were part of a tidally influenced, mostly freshwater estuary. “When the tide went out, terrestrial animals could walk out on the mudflats and fish would swim in the shallow water. Both would leave traces of their activities in the mud,” Buta said. “The traces would be quickly buried in thin layers of sediment that had eroded from the nearby Appalachian Mountains, and this led to their preservation as fossil trackways.” Tracking ancient creatures Trackways provide evidence of movement and other behavior at a specific location in time, the story of life hundreds of millions of years ago, he said. No bone or body fossils of four-legged animals from the Coal Age in Alabama have been found. Knowledge of the tetrapod (four-legged) animals of this period in Alabama is based solely on information gained from trackways, Buta said.

“Most fossils of bone and body are a record of an animal’s death. But fossil tracks tell us about a creature’s behavior at a time it was living,” he said. “We can see or infer its actions, how fast or slow it was moving, and whether it was interacting with other creatures or even different species. That’s one of the primary fascinations of this record.” Coal mines provide one of the few windows into the geological past. The giant drag lines that gouge the earth uncover seams of coal, formed from lush forests. But the window to explore the layers of coal, shale and other rock closes quickly, because federal environmental protection law requires surface mines to be returned to their previous natural state within a few years after the coal is removed. How the Union Chapel Mine was saved from that fate is a tale spurred by a unique mobilization of amateur and professional rock hounds. The first reptiles Now named in memory of one of the amateur fossil enthusiasts who worked to save it, the Minkin Site is under the protection of the Alabama Department of Conservation and Natural Resources, Division of Lands. The Alabama Paleontological Society conducts tours and manages access to the site, and visitors may keep fossils unless they are unusual enough to deserve further study.

Kopaska-Merkel said the site has “an amazing number of fossils, important because it allows us more data points for comparisons. For example, we can see if an animal’s behavior changes as it grows. And the diversity of species is important, too. “Ron recently found a second fossil site 23 miles away near Carbon Hill that is from the same time period that also includes a lot of trackways. However, almost all the fossils are from a single species, whereas the Minkin site allows us to see what different kinds of creatures were living together in that ecosystem,” he said. “This deposit was laid down right after the first reptiles evolved. It shows tracks of amphibians and tracks of reptiles together, sometimes on the same piece of rock,” Kopaska-Merkel said. “So it’s a window into that time reptiles were just starting to take over the land and interact with amphibians.” Public access Tetrapod trackways were discovered in Alabama coal mines almost 100 years ago but did not begin to be studied extensively until Allen explored the Union Chapel Mine hoping to find fossils to show his science students. “It was a ‘yahoo’ experience,” Allen said. “There were trackways almost everywhere.”

He showed samples to the Birmingham (later Alabama) Paleontological Society, which led an effort to quickly collect more than 1,000 fossils, document the findings and get academic concurrence that the fossil trackways were important. “There were so many fossils that we held a series of ‘track meets’ to organize them. A key decision was to put pictures and descriptions on the internet, making it possible for anyone to study and comment on them,” Allen said. The group also agreed for many of the samples to be publicly available, rather than held in private collections. They can be seen at the Alabama Museum of Natural History in Tuscaloosa, the Anniston Museum of Natural History and the McWane Science Center in Birmingham, as well as at the interactive, online atlases of the Minkin Site and the Carbon Hill site. “Alabama is recognized as a hot spot for fossil collectors,” Buta said. “Our geology is so diverse that there are plenty of different rock formations to interest amateurs and professionals. Now there is increasing interest in fossil trackways.” Allen added, “This is simply a superb place to look at the ecosystem of the Coal Age. Many spots show one component of the ancient environment, but the Minkin Site allows us to see a much more complete picture of what was going on at this time as new forms of life were emerging on Earth.”

http://alabamanewscenter.com/2016/07/22/footprints-in-stone-fossils-of-coal-age-animals-attract-global-visitors/