BONNER SPRINGS SHALE (UPPER PENNSYLVANIAN) FOSSIL ASSEMBLAGE IN A MAZON CREEK-TYPE DEPOSITIONAL ENVIRONMENT 

*Edinger, P.V., J.C. Gleason, S.A. Hageman, O.L. Hull, J.R. Martin, M.W. Price, and B.W. Skelton
Department of Natural and Physical Sciences, Park University.

The understudied Bonner Springs Shale Member (Kansas City Group) outcropping in Parkville, MO represents a Mazon Creek-Type depositional setting.  The high quality of preservation and diversity of the fossil assemblage provides a unique opportunity for paleoenvironmental reconstruction.  It is interpreted as a deltaic setting after assessing the quality of preservation, sedimentary structures, and lack of in situ fossils.  Preservation is commonly due to carbonization and its quality is attributed to rapid burial in anoxic conditions.  The anoxic setting is due to salinity stratification occurring in this estuarine environment which explains the presence of few in situ fossils. The fossils appear to be terrestrial in origin but gently transported a short distance by a fluvial source into this estuarine setting.  This is supported by cyclic tidal rhythmites, absence of bioturbation, occasional sandstone lenses (flooding events) and an absence of coal.  Collections were taken at 1 m intervals, resulting in eight vertical and seven horizontal samples, to study transitional changes.  Sampling revealed plant accumulations were sporadically distributed in isolated concentrations that typically consisted of finer grain mud and silt.  Accumulations were non-species specific, suggesting that plants were washed in as unsorted mats.  The 550 fossils specimens used to assess the assemblage resulted in: lycopods (27.1%), Cordaites (23.6%), seed ferns and true ferns (22.7%), sphenopsids (21.5%), and seeds (3%).  Insect wings (1.5%) and trace fossils (0.5%) are present but scarce.  The most common wing was that of a new species of cockroach, Sysciophelbia sp. n.