HIERARCHICAL SPATIAL PATTERNS IN PALEOCOMMUNITIES OF THE LATE PENNSYLVANIAN AMES LIMESTONE

Ancient and modern marine organisms have structured spatial distributions as a response to environmental signals that result in characteristic species associations in different geographic locations. In this study, the Upper Pennsylvanian Ames Limestone was analyzed along its depositional strike to understand the spatial heterogeneity of Ames paleocommunities. This widespread carbonate unit of the Ames Member of the Conemaugh Group (=Ames Limestone) is the uppermost unit of the Glenshaw Formation and records the maximum flooding interval of a glacioeustaticaly influenced fifth order sea level cycle. Statistical analyses based on taxa abundance and guild analysis provide insight on how taxa partitioned the ecospace during deposition of the Ames Limestone.

To assess the paleocommunity structure and its variability at multiple spatial scales, field data were collected at seven outcrops of the Ames Limestone in the southeastern Ohio. These localities form a northeast to southwest trending transect along the northwestern outcrop belt of the Conemaugh Group parallel to the strike of the original depositional basin. Invertebrate fossils were identified in the field and abundance counts were recorded for discrete taxa. Taxa identified include rhynchonelliform brachiopods, bivalves, gastropods, bryozoa, corals, crinoids, regular echinoids, trilobites and foraminifera. Quantitative analyses were implemented within the R programming language and the software PAST. Statistical analyses of the abundance data within the combination of spatial scales (within a single outcrop, among sites and within the total study area) provide insights on geographic partitioning of community variation.

Initial detrended correspondence analysis(DCA) and cluster analysis indicate a clear partitioning of communities in geographic space between northeastern and southwestern study sites. Final results of this study will provide a framework for understanding paleocommunity structure of the Ames Limestone highlighting the key ecologic mechanisms that drove these variations along a variety of hierarchically arrayed spatial scales.