Show-Me State Times

Researchers from the University of Missouri are collaborating with geologist Gordon Baird to reanalyze a massive fossil collection from the Mazon Creek site, currently housed at the Field Museum in Chicago. This collection includes 300,000 siderite concretions from around 350 different localities.

The Mazon Creek fossil beds are known for their exceptional preservation of both plants and animals due to their unique geological setting. The fossils are encased in siderite, an iron carbonate mineral, forming abundant concretions that have become valuable for scientists and fossil hunters.

Baird's original work at Mazon Creek distinguished two major faunal assemblages, which helped scientists understand the ancient environments where the fossils originated. These were a marine assemblage comprised of life in offshore coastal waters and a mixed assemblage from a river delta along the shoreline.

The team at Mizzou has confirmed a slightly more nuanced view using modern data analysis techniques and advanced imaging. "We found three readily identifiable paleoenvironments," said Jim Schiffbauer, Marie M. and Harry L. Smith Endowed Professor of Geological Sciences.

Schiffbauer explained that these ancient environments were each dominated by specific groups of animals, such as freshwater animals nearest to shore and jellyfish further offshore. The fossils formed during sea-level rise phases that flooded large coal swamps.

In future research, Schiffbauer and Baird aim to create a sedimentological model connecting the Mazon Creek ecosystem to the Colchester coal layers below. "Refinement of information from the Mazon Creek locality will lead to a deeper understanding of similar deposits," said Baird.

Mizzou’s new collaborative analysis is considered comprehensive and data-driven regarding what Mazon Creek’s ancient ecosystem looked like long ago. "It offers a real snapshot of diversity present in the late Carboniferous Period," Schiffbauer noted.

The study was published in Paleobiology with co-authors including John Warren Huntley and Tara Selly at Mizzou; Charles Chabica at Northeastern Illinois University; Marc Laflamme at University of Toronto Mississauga; and A. Drew Muscente at Princeton Consultants, Inc.