SYSTEMATICS AND GROWTH FORM ANALYSIS OF STROMATOPOROIDS OF THE LITTLE CEDAR FORMATION MIDDLE DEVONIAN, EASTERN IOWA

The purpose of this study is to perform a systematics and growth form analysis on stromatoporoids from biostromal units in the Little Cedar Formation (Solon and Rapid Members), which crop out around Johnson County, Linn County, and Benton County in east-central Iowa. The study also seeks to determine the environmental conditions that occurred locally and to document the diversification and extinction patterns of stromatoporoids during the Middle Devonian. Samples from the Little Cedar Formation were collected in quarry and road cut sections using a transect line approach. Longitudinal thin sections were made of all the stromatoporoid samples for use in species identification, and rock samples were examined to assess environmental conditions. Gallery, pillar, and lamellae structures of the stromatoporoids are measured using NIH image. Cluster analyses, principal component analyses, and discriminant analyses of these measurements are used to identify and describe stromatoporoid species. Rock samples were used to characterize growth forms and assess how they vary in relation to the local environment within and between the biostromal units. Diversity and extinction patterns of Middle Devonian stromatoporoids are documented by comparing the findings of this study to those published in the literature.