MULTISPECIES TAPHONOMY AND PALEOECOLOGY OF THE LATE CARBONIFEROUS CARBONDALE GROUP, CENTRAL ILLINOIS

The Late Carboniferous Carbondale Group crops out in West-central Illinois near the city of Peoria, and contains a diverse, well-preserved fauna of brachiopods, crinoids, corals, gastropods and cephalopods. The enclosing rock types are shales, calcareous shales and limestones, interpreted as being deposited in the deeper portions of the Illinois Basin. Shales were soaked in Stoddart Solvent, sieved, sorted, identified and counted for all paleoecologic and taphonomic analyses. The fauna is dominated by immobile, epifaunal, suspension-feeding taxa. Articulate brachiopods comprise over 50% of all species, with Marginifera, Crurithyris and Neospirifer especially abundant. As a grouping, the brachiopods are slightly corraded (corrasion level II), carinate + splayed fractured, and slightly encrusted by epibionts (epibiont coverage levels 1 and 2). These taphonomic data suggest short residence times on the sea floor due to moderate to high sedimentation rates. Comparison to the Carboniferous (Virgilian) Gaptank Fm. of West Texas, Carboniferous (Missourian) Graford Fm. of North-Central Texas and Permian (Leonardian) Coyote Butte Fm. of Central Oregon reveals similarities and differences with these different age/environment faunas.