SUBSURFACE MISSISSIPPIAN LITHOSTRATIGRAPHY BASED ON CORES FROM SOUTH-CENTRAL KANSAS AND THEIR COMPARISON TO OUTCROPS

The lithostratigraphy of Kinderhookian to Osagean rocks in subsurface south-central Kansas (Barber County) is clarified based on numerous cores, and their comparison to the stratigraphy of Mississippian rocks exposed in SW Missouri, NW Arkansas and NE Oklahoma. As on the outcrop, these cores were from the critical transition zone from shelf facies to the north and presumed deeper-water facies to the south, and we can now directly correlate the stratigraphy of these subsurface rocks to outcrops more than 200 miles to the east. Hence, we urge abandonment of the vague and confusing existing stratigraphic assignments in this part of the subsurface Mississippian section in Kansas.

The subsurface Kinderhook shale is much thicker than its outcrop equivalent – the Bachelor Shale. The successively overlying Kinderhookian Comptom Limestone and Northview Fm. are recognized in the subsurface as shaly limestone and silty to shaly limestone, respectively. The disconformity present within the Compton in outcrops likewise is traced into subsurface Kansas. Reddish, shaly limestones present locally within the subsurface Northview Fm. are correlative to the Baird Mountain Fm. in outcrops, which is a facies of the Northview. The overlying lower Osagean Pierson Limestone in the subsurface is non-cherty to only slightly cherty, coarse crinoidal limestone that passes basinward into micritic limestone. The latter lithology is not present in outcrops because of syndepositional tectonic control on deposition of this unit. The unconformity within the Pierson that is present in outcrops likewise is inferred in the subsurface. The overlying Reeds Spring Fm. is lime mudstone with abundant dark and light gray, multi-generational hert with conspicuous burrows, and these attributes are identical to those in surface exposures of this formation. The Cowley Formation, a major oil and gas reservoir in subsurface Kansas and northern Oklahoma, is an unconformity-bounded unit within the Reeds Spring Fm. Younger Osagean rocks correlative to the Burlington-Keokuk Fm. in outcrops are not present in the immediate subsurface study area because of erosion, although they are present regionally in Kansas.