A PETROGRAPHIC AND TAXONOMIC ANALYSIS OF A FOSSIL PLANT ASSEMBLAGE FROM THE WINTERSET MEMBER (KANSAS CITY GROUP), KANSAS CIT, MISSOURI

A variety of fossilized plant material was collected from the upper Winterset Member (Kansas City Group; Pennsylvanian) near the intersection of View High Drive and Interstate-470 in Kansas City, MO. The Winterset is predominantly a carbonate corresponding to the Missourian (Kasimovian) Stage. Although fossilized plants have previously been reported in the Winterset, this study is the first to report fossilized plant material in such high concentrations and diversity. The upper Winterset, where plant fossils were collected, is a tan to light gray, thin-bedded marine carbonate. Petrographically, the carbonate has been identified as a micrite, or mudstone, consisting of a fine-grained calcite-clay matrix, and marine microfossils (replaced by microcrystalline quartz). Fossilized plant parts have been tentatively grouped into five different terrestrial genera: Cordaites, Neuropteris, Macroneuropteris, Pecopteris, and Alethopteris. Although leaves are most abundant, there are several non-leaf plant parts (stems and seeds) of unknown taxonomic origin that have been observed, as well as finely disseminated organic debris. The dark colored leaves and organic debris are distinctly observable against the tan to light gray matrix. The occurrence of a diverse fossil plant assemblage in a carbonate mudstone is atypical and presents an opportunity to further investigate the nature of deposition and environmental conditions during the Missourian Stage. Based on preliminary data, we hypothesize plant material was transported and deposited in a lagoon after a continental storm.