Refining the Mississippian-Pennsylvanian Systemic Boundary in Western and South Central Kentucky
Michael T. May1 and Scott Schoefernacker2
1Western Kentucky University, Dept of Geography & Geology, Bowling Green, KY 42101, [email protected]
21132 Wellsville Road, Memphis, TN 38117, [email protected]
The basal Pennsylvanian Caseyville Formation of southcentral and western Kentucky includes an extensive network of paleochannels, which unconformably overlie various Mississippian (Chesterian Series) rocks. The extent and orientation of paleochannels and the systemic boundary in the region is problematical in cases where marker beds are lacking or where sandstone facies of Pennsylvanian age overlie lithologically similar Mississippian-age strata. Discerning the systemic boundary may also be complicated by facies changes in Chesterian strata. This study employs various data to investigate the Mississippian-Pennsylvanian systemic boundary such as well logs, outcrops, and subsurface-to-outcrop cross-sections and some recent (2009) faunal zonation established along the Natcher Parkway between Morgantown and Bowling Green, Kentucky. Subsurface and outcrop investigation was aided by use of the Kentucky Geological Survey's Digitally Vectorized Geological Quadrangles (DVGQs) and the Indiana Geological Survey’s Stratigraphic Column Generator. An ongoing research effort by students at Western Kentucky University continues to refine the trunk and tributary systems. Trunk fluvial systems have a maximum incisement of 113 meters (370 feet) and many tributary systems exceed 60 meters (197 feet) depths. Results of this study provide a better understanding of the sub-Pennsylvanian topography that is dependent on lithologic variation and weathering of Upper Mississippian strata. Mapping of paleochannel systems continues to be economically important in the Illinois Basin region for development of groundwater and hydrocarbon resources.
AAPG Search and Discovery Article #90095©2009 AAPG Eastern Section Meeting, Evansville, Indiana, September 20-22, 2009