HIGH RESOLUTION STRATIGRAPHY OF THE ST. JOE GROUP FROM SOUTHWEST MISSOURI TO NORTHEAST OKLAHOMA

Lower Mississippian strata in the tri-state region of Missouri, Arkansas, and Oklahoma include the Bachelor Formation, Compton Formation, and Northview Formation of Kinderhookian Stage, as well as the Pierson Formation, Reeds Spring Formation, and the Bentonville Formation of Osagean Stage. Collectively the Bachelor-Pierson Formations make up the St. Joe Group and were deposited on a shallow marine carbonate ramp, known as the Burlington Shelf. These beds regionally thin in a south-southwest direction from Jane, Missouri, towards Siloam Springs, Arkansas, and continue into northeast Oklahoma, as well as to the south-southeast direction into Batesville, Arkansas.

Several workers have noted unique changes in thickness, facies variations, unconformities, and northward-dipping progradation of the St. Joe Group in this region. Some hypothesized that the southward regional thinning is possibly due to marine condensed sedimentation into a starved basin or alternatively thinning over a structural high.

Seven stratigraphic sections were chosen from southwestern Missouri to northeastern Oklahoma for detailed lithologic and petrographic analysis to gain a better understanding of the motif behind the thinning of these strata. The petrographic data presented in this report provides evidence that these deposits contain moderate to high energy skeletal wackestones and packstones that indicate a shallow marine ramp depositional environment. Other lines of evidence that these deposits are of shallow marine origin include green calcareous shale, greenish-blue pisoids, peloids, and quartz silt commonly seen throughout the St. Joe Group. These characteristics favor the proposition that these strata are thinning over a fore-bulge high due to syndepositional tectonism associated with the Ouachita Orogeny. This orogeny created fore-bulge arches that overprinted lithostratigraphic and sequence stratigraphic architecture of the St. Joe Group.