Abstract

An updated high-resolution zonation for the Middle Tournaisian-lower Visean (middle Kinderhookian-basal Meramecian) strata of the western flank of the Ozark Uplift is presented herein. The Middle Tournaisian (Tn2-middle and upper Kinderhookian) zonation from oldest to youngest includes the Siphonodella sandbergi-S. duplicata Zone, Siphonodella lobata-S. crenulata Zone, Siphonodella cooperi-Gnathodus delicatus Zone, and the Siphonodella cooperi hassi-lower Gnathodus punctatus Zone. These zones are identical to those proposed by Thompson and Fellows (1970). The Upper Tournaisian-basal Visean (Tn3-Osagean), zonation from oldest to youngest includes the Polygnathus communis carina-upper Gnathodus punctatus Zone, Lower Pseudopolygnathus multistriatus Zone, Upper Pseudopolygnathus multistriatus-Gnathodus cuneiformis Zone, Scaliognathus anchoralis-Doliognathus latus Zone, Bactrognathus distortus lanei Zone, Polygnathus mehli-Gnathodus sublineatus Zone, Gnathodus bulbosus Zone, Lower Gnathodus “texanus” Zone, Middle Gnathodus “texanus”-Gnathodus texanus pseudosemiglaber Zone. The Upper Pseudopolygnathus multistriatus-Gnathodus cuneiformis Zone, Lower Gnathodus “texanus” Zone, and Middle Gnathodus “texanus”-Gnathodus texanus pseudosemiglaber Zone are newly proposed herein.

Application of this new zonation to the Kinderhookian-lower Meramecian strata of the western Ozarks and Midcontintent basins demonstrates the highly diachronous nature of the Pierson Formation, Reeds Spring Formation and the Bentonville Formation (formerly Burlington and Keokuk Formations). Additionally, detailed surface and subsurface application of this zonation shows that diachronous prograding carbonate wedges typify the depositional motif of Osagean strata. This progradation served to compartmentalize hydrocarbon reservoirs, thus complicating exploration and production efforts.

Utilization of the new zonation additionally shows and dates penecontemporaneous tectonics within Osagean strata and aids in the development of a tectonic-sedimentologic control mechanism for the patterns of reservoir development.