Abstract

Lithologies, depositional environments, stratigraphic architecture, and conodont biostratigraphy of Lower to Middle Mississippian rocks in the western Ozarks comprise five depositional sequences in ramps on the southern Burlington shelf. Aggradational ramps in the Kinderhookian to early Osagean St. Joe group were relatively strongly overprinted by Ouachita-related tectonism involving inferred recurrent passage of fore-bulge highs and associated basins across central and southern parts of the outcrop area. Significant effects of tectonism are southward facies shallowing onto the broad Kanoka ridge paleotopographic high associated with locally extensive marine and lesser subaerial erosion, sediment thickening and deposition of generally northward down-lapping, resedimented wedges with dislodged reef blocks and conglomerates into relatively rapidly subsiding basins, and formation of a regionally extensive paleosol at the top of the group. Back-stepping subsidence due to middle Osagean foundering of the Kanoka ridge was followed by rapid, long-distance progradation of middle- and outer-ramp facies in the Bentonville and Reeds Spring limestones. Tectonism at this time resulted variously in local folding, uplift, marine and subaerial erosion, and reversal of shelf bathymetry. Southward erosion of the Reeds Spring and Bentonville occurred at least in Oklahoma on rejuvenated segments of the Kanoka ridge. Overlying lower Meramecian limestones are shallow-water deposits truncated by a major unconformity.