Chapter 13: Paleoecology of the Pennsylvanian Period in Illinois and Adjacent States

The Pennsylvanian System in Illinois and adjacent States offers an excellent opportunity for the study of paleoecology, but any interpretations made at this time must be based on data gathered during conventional stratigraphic work. The paleogeography, deformational movements, and stratigraphic composition of the Pennsylvanian are reviewed because they furnish necessary background. Ecological factors are listed and discussed with particular reference to the Pennsylvanian and their importance in controlling the composition and distribution of biotas. Pennsylvanian pelagic environments, the lithologic associations of marine species, and the nature of terrestrial environments are considered. The characteristics and peculiarities of all the generally recognized members of the Pennsylvanian cyclothem, as developed in Illinois, are briefly described and interpreted. The inferred succession of Pennsylvanian climates in North America is reconstructed. Methods of attacking the study of Pennsylvanian paleoecology are outlined. An appendix briefly presents the argument for diastrophic control of Pennsylvanian cyclothems.