Petrology and Weathering Environment of sub-unconformity limestone unit: The Kessler Limestone Member of the Bloyd Formation, Morrowan (Pennsylvanian) Northwest Arkansas

In northwest Arkansas the thin, widespread Pennsylvanian Kessler Limestone of the Bloyd Formation is exposed in numerous locations. Comparison of various exposures shows the Kessler is heterogeneous in thickness and lithology. Thickening of the Kessler occurs southward into the Arkoma Basin where the interval has been commonly used as a horizon for natural gas exploration.;The Kessler Limestone is underlain by the Dye Shale Member of the Bloyd Formation and overlain by the Trace Creek Shale of the Atoka Formation. The contact between the Kessler Limestone Member and the Trace Creek is a regional unconformity in the midcontinent, marked by a manganese-enriched crust filled with various nodules and concretions.;Methods used in this study began with reviews of previous investigations of the Kessler Limestone and followed with a petrographic analysis of the interval. To further this study, the contact between the Kessler Limestone and the Trace Creek Shale was examined in three locations; I-49 Road-cut, Evansville, and Patrick. Examining this contact may better define the changes produced by Pennsylvanian weathering and the environmental conditions that resulted in the regional sub-unconformity.