Conodont Biostratigraphy in Middle Osagean to Upper Chesterian Strata, North-central Oklahoma, U.S.A.

Abstract

The informally known “Mississippian Limestone” stratigraphic interval in north-central Oklahoma, U.S.A. bears no chronostratigraphic markers and has no formally established biostratigraphic framework to date. Conodonts collected from four “Mississippian Limestone” cores in Logan, Payne, and Lincoln Counties provide the means for better constraining the stratigraphic age of the interval over the area studied. Conodont extraction was conducted by acid digestion of whole-rock samples and heavy liquid density separation after which conodont genera and species types were identified from scanning electron microscopy. Biostratigraphically significant conodonts recovered in combination with chemostratigraphic work by Dupont (2016) and earlier studies by Thornton (1958), Curtis and Chaplin (1959), McDuffie (1959), Rowland (1964), Selk and Ciriacks (1968), and Harris (1975) indicate the “Mississippian Limestone” ranges from middle Osagean to late Chesterian in age. In general, conodont element recoveries were too low in quantity and too poor of quality for use as biostratigraphic markers. The relatively low recovery and poor preservation quality of the conodont elements are attributed primarily to the elements being reworked soon after deposition by frequent storms on a mid- to outer-ramp environment in a low-latitude carbonate ramp setting. The results of this investigation are most significant in that they help place Mississippian deposition over the area studied within the context of a global Carboniferous stratigraphy. The results also allow for the Mississippian interval in the study area to be more accurately related to time-correlative strata with similar or better age constraint for constructing more temporally meaningful depositional models of the Oklahoma basin.