UPPER VISÉAN (MERAMECIAN-CHESTERIAN) CONODONT BIOSTRATIGRAPHY OF THE SOUTHWESTERN OZARKS OF NORTHEASTERN OKLAHOMA, SOUTHWESTERN MISSOURI, AND NORTHWESTERN ARKANSAS

Informal, and often erroneous, usage of lithostratigraphic and chronostratigraphic terminology for Mississippian rocks in the subsurface of Oklahoma is pervasive and counterproductive. Upper Viséan (Meramecian-Chesterian) rocks consisting of the upper Boone Group and Mayes Group, equivalent to a significant portion of the subsurface Mississippian section, are exposed along the western edge of the Mississippian outcrop belt in the southwestern Ozarks of northeastern Oklahoma, southwestern Missouri, and northwestern Arkansas. These rocks represent cost-effective and impactful sources of data which enhance our understanding of southern Mid-Continent geology and the application of this understanding to hydrocarbon exploration.

In this presentation we describe conodont recoveries from the upper Boone Group and Mayes Group and the subsequent definition of four provincial conodont biozones (and three subzones). Biozone 1 and Biozone 2 are present in the upper Boone Group (Meramecian). Biozone 3 (latest Meramecian) is present within the lowermost Mayes Group, the base of which is characterized by an important regional unconformity. Biozone 4, representing a major faunal shift, includes the remainder of the Mayes Group and is early to middle Chesterian in age. The top of Biozone 4 appears to coincide with the Mayes Group-Fayetteville Shale contact. Biozone 4 is divided into three subzones based on subtle faunal changes. Although biozone boundaries often coincided with unconformities, which imparts a degree of bias to biozone definitions, conodont data from these rocks were vital in resolving stratigraphic relationships within the outcrop area and remain viable in terms of their potential utility in correlations and interpretations of time-equivalent strata in the subsurface of Oklahoma. These results represent just a part of a larger ongoing investigation concerning the conodont biostratigraphy of the upper Viséan (Meramecian-Chesterian) rocks in the southern Mid-Continent.