Remnants from a cave embedded in a limestone quarry southwest of Chicago have yielded a fossil trove that may influence the known history of north central Illinois some 310 million years ago.Plotnick and a group of students discovered the cave while on a class field trip about four years ago. It is revealed by darker color surrounded by the lighter limestone, and by the sand and mud containing fossilized material that choke the cave from bottom to top.
"What's really valuable about the cave is the level of preservation of the material," said co-presenter Kenig. "We see charcoal that preserves biological features at the cellular level. Charcoal is an indication of fire burning ancient trees. The cave also beautifully preserved molecular indicators of these fires."
Findings include nearly-pristine plant spores, leaves and scorpion parts. Needles from a conifer were dated and discovered to be the oldest ever from North America. "The oldest conifers previously described are at least 2 million years younger," said Plotnick. The specimen is now in the collection of Chicago's Field Museum.
The scientists think that a shallow sea covering today's north central Illinois during the geological Ordovician period about 450 million years ago formed the limestone. The caves were eroded in the limestone at the beginning of the Pennsylvanian period, about 315 million years ago. Within a few million years, sand, mud and organic debris from plants and animals -- some burned and turned to charcoal -- washed into the cave through surface openings, where it remained preserved but not compacted since that time. link
Initial research findings were presented April 12 by University of Illinois at Chicago earth and environmental sciences professor Roy Plotnick at a regional meeting of the Geological Society of America in Lawrence, Kan.