Degree Name
Master of Science (MS)
Semester of Degree Completion
1992
Thesis Director
Raymond N. Pheifer
Abstract
The primary objective of this study is to reconstruct the paleofloristics of an unnamed shale of lower Middle Pennsylvanian age. The shale is periodically exposed in the highwall of the Ashboro Pit, Log Cabin Coal Company, Clay County, Indiana. This will be the first upland fossil flora to be described from the eastern margin of the Eastern Interior Basin (Illinois Basin). The gray shale containing the upland flora lies directly above the Upper Block Coal (SW 1/4, SE 1/4, sec. 17, T. 11N., R. 6W.)
Two collections, collected on three different occasions were made available for analysis: Smithsonian Natural History Museum (1980, 1982) and Illinois State Museum (1978). The facies that contained this upland plant association could not be relocated. Numerous attempts were made between Fall 1989 through Spring 1991. It is believed that the facies was discontinuous and was not present in the exposed highwalls of the mine during the times examined.
A complete historical literature review on this particular paleoflora was conducted, particularly those citations of Megalopteris and Lesleya. Comparisons of upland associations in other parts of the Illinois Basin, for example Rock Island County, Illinois, as well as similarities and differences among other Pennsylvanian paleofloras are discussed. Significant fossils identified from the Smithsonian and Illinois State Museum Ashboro collections are: Lepidostrobophyllum, Sigillaria, Sphenophyllum cuneifolium, Alethopteris lonchitica, A. serli, Aulacotheca, Eusphenopteris morrowensis, Lesleya cheimarosa, Megalopteris southwellii, Neuropteris heterophylla, Pecopteris serrulata, P. plumosa, Cardiocarpus, Cordaianthus, Cordaites principalis and Samaropsis. Within the two collections there exists specimens that have never been associated with an upland floral association. These specimens are: Alethopteris missouriensis, Neuropteris obliqua, Neuropteris ovata, Callipteris flabellifera var. moorei, Asterophyllites charaeformis, Sphenophyllum majus, Carpolithus, and Calamites. The environmental interpretations suggest the dark shale facies that contained the fossils represented a more organically rich, less oxygenated, low energy depositional environment. The light, fine grained shale is indicative of a high moving stream, less organically rich, more oxygenated. Preservation of the floral association did not appear to differ in respect to the different color or grain size. Upland floras were considered to be much more sensitive to environmental variations than swamp floras, therefore more likely to be the gene pool from which evolutionary advances were destined to occur.
Recommended Citation
Comer, Vicki J., "The First Documentation of a Lower Middle Pennsylvanian Upland Flora from the Eastern Margin of the Eastern Interior Basin (Illinois Basin)" (1992). Masters Theses. 2138.
https://thekeep.eiu.edu/theses/2138
