USE OF STRATIGRAPHIC ANALYSIS TO RECONSTRUCT THE PENNSYLVANIAN DEPOSITIONAL HISTORY OF WESTERN PENNSYLVANIA

Strata of McConnell’s Mill State Park provide an excellent opportunity to reconstruct the depositional history for west-central Pennsylvania during Lower Pennsylvanian time. Research was conducted in the fall of 2002 at McConnell's Mill State Park, Lawrence County, Pennsylvania by eleven Slippery Rock University Sedimentology and Stratigraphy students. Preliminary results indicate that at McConnell’s Mill State Park, three phases of deposition occurred along the northern margin of the Dunkard Basin as a result of a transgressing sea. The first phase is characterized by deposition of the Homewood Sandstone within a gently dipping broad braided stream system. This facies consists of cross-stratified quartz arenites interbedded with massive, planar and trough cross-stratified arenites. Coal-rich micaceous sandy shales and siltstones reflecting floodplain, interdistributary bay or prodelta deposition, differentiate the second phase. The third phase records deposition of a shallow marine brachiopod, pelmetazoan wackestone characteristic of the Vanport Limestone. Pennsylvanian sediments of the Pottsville and Allegheny Groups exposed at McConnell’s Mill State Park resulted in a shift from predominately fluvial conditions during deposition of the Homewood Sandstone, to lower delta plain/prodelta during deposition of the Clarion Formation and shallow marine conditions during deposition of the Vanport Limestone.