A Middle Pennsylvanian Nodule Flora from Carterville, Illinois

Abstract

As early as 1875 the occurrence of small, irregularly-shaped nodules of pyritiferous clay in which fossil plants could be found, had been reported in the roof shales of the Herrin (No. 6) Coal at Carterville, Illinois. Active collection of these plant bearing nodules began nearly 15 years ago, and at present over 2500 specimens are curated in the Southern Illinois University paleobotanical collection. The impression-compression ironstone concretion flora is Middle Pennsylvanian in age, assigned to the Carbondale Formation, Kewanee Group. The completed floristic survey encompasses 1,475 specimens delegated to 24 genera and 52 species. Specimens not able to be placed in a taxonomic rank were assigned to form status. The flora is dominated (44% of all specimens assignable to a generic status) by Filicalean and Marattialean elements of the genus Pecopteris Brongniart. Medullosan pteridosperm taxa, Neuropteris (Brongniart) Sternberg, Alethopteris Sternberg, Odontopteris Sternberg, and Callipteridium Weiss compose nearly 25% of the flora. Few Lyginopterid elements have been encountered. Calamitean components are relatively abundant in the forms of Annularia Sternberg, Asterophyllites Brongniart, and Calamites Suckow, while Sphenophyllalean taxa are rare. Isolated sporophylls dominate the Lepidodendralean aspect of the flora. The assemblage exhibits an abundance of Upper Allegheny and Lower Conemaugh plants, and has been equated to the Upper Kittanning Coal of the Appalachian Region.