PALEOENVIRONMENTAL INTERPRETATION OF SILICICLASTIC DEPOSITS ON THE CHEROKEE SHELF DURING MIDDLE PENNSYLVANIAN SEA LEVEL TRANSGRESSION, BANDERA SHALE FORMATION (SOUTHEASTERN KANSAS AND NORTHEASTERN OKLAHOMA)

In southeastern Kansas and northeastern Oklahoma the under studied Bandera Shale Formation (BSF) (Middle Pennsylvanian) is stratigraphically located between the underlying Pawnee Limestone and overlying Altamont Limestone Formations of the Marmaton Group. Predominately siliciclastic units of shale, sandstone, and coal ranging from 12 cm to 20 m thick crop out from Linn to Labette Counties in Kansas and in Nowata County, Oklahoma. Previous studies from rock exposures interpreted the BFS as non-marine in origin; whereas, subsurface log analysis has interpreted it as mainly marine in origin. Extensive field and laboratory analyses of previously undescribed BSF exposures in Kansas and Oklahoma provide a more comprehensive interpretation of the paleoenvironments and sedimentary processes that deposited these rock units on the Cherokee Shelf.

Results from 6 new stratigraphically measured exposures, lithologic/petrographic analyses, sedimentary structures, and fossil evidence indicate that variability in the BSF resulted when transgressive processes overwhelmed siliciclastic sedimentation in progradational marginal marine environments. Paleocurrent indicators, sediment lithology and distribution in lower units of the BSF suggest a northeasterly provenance for deposition of deltaic siliciclastics. Eastern coal beds grade laterally into thick, cross bedded and splayed sandstones that grade southerly into a thin (>10 cm) black shale in the Oklahoma Arkoma Basin; whereas, upper units consist of massive, reworked sandstones that grade stratigraphically upward into organic rich gray shales indicative of transgressive sea level. Results of this study serve to re-interpret the environments of deposition of the BSF. The complex sedimentary architecture of the BSF and similar deposits are related to sea-level fluctuations, facies relationships, and siliciclastic deposition on an intracontinental shelf during the Pennsylvanian.