High Resolution Correlation of the Shawnee Group (Virgilian, Pennsylvanian) Cyclothems from Northwestern Missouri to Exposures in Southern Kansas and Northern Oklahoma

Abstract

The Shawnee Group extends from Oklahoma through Kansas, Missouri, Iowa, and Nebraska. In Oklahoma much of the terminology differs from that of the other states. Three of the megacyclothems within the Shawnee Group were examined in Kansas, Oklahoma, and Missouri. They were correlated based on lithology, gamma-ray analysis and conodont distributions to create the same terminology for Oklahoma units. Within the Oread megacyclothem there are changes in thicknesses southward into Oklahoma with the presence of more sandstone. This is seen especially well in the Heebner member which increases from five to sixty feet. The Toronto and Stull members of the megacyclothem may be lenticular, as they are not present at all localities. The Spring Branch member up to and including the Big Springs member of the Lecompton megacyclothem appear as lenses in Oklahoma, similar to the lower member of the Oread megacyclothem. The Queen Hill member has also changed in Oklahoma, from black fissile shale with gray clay shale at the top to a red paleosol at the base and black shale at the top. The Shawnee Group can be correlated based on gamma-ray analysis, lithology, and conodont distributions into Oklahoma. The three core shales within the three formations studied can be traced into Oklahoma and are present. Each looses it fissility southward and its carbon content decreases so much in places, that it becomes a gray shale. Both marine flooding surfaces and surfaces of maximum regression can be traced throughout much of the outcrop area.