Carboniferous Mason Creek Biota
You may have seen some lovely plant material in dark nodules of siderite or iron carbonate coming from the Mazon Creek Fossil Beds. the Mason Creek Biota are lovely fossil lagerst\xe4tte found in northeastern Illinois. These marine and terrestrial fossils are preserved in ironstone concretions that tell the tale of our world some 309 million years ago \u2014 back in the Carboniferous.