HIGH-RESOLUTION CONODONT BIOSTRATIGRAPHY OF THE EARLY CARBONIFEROUS, TOURNAISIAN STAGE, CHESTNUT RIDGE SECTION IN SOUTHWEST MISSOURI

The goal of this project is to establish high-resolution conodont biostratigraphy of the Middle-Upper Tournaisian (early Carboniferous) at the Chestnut Ridge roadcut along U.S. Highway 65, roughly 30 miles south of Springfield, MO. This is part of a larger project to determine carbon and oxygen isotope stratigraphy of the early Carboniferous of Southwest Missouri across the Tn2-Tn3 (Kinderhookian-Osagean) boundary. Previous studies at the Chestnut Ridge locality have established low-resolution biostratigraphy of exposed early Carboniferous strata from the Bachelor Formation through the Elsey Formation.

Thirty-six samples were collected at ~0.3 meter intervals at the Chestnut Ridge section from the Bachelor Formation through the Pierson Formation. Samples were dissolved using formic acid and separated by density using acetylene tetrabromide. Conodont platform elements were isolated and identified to species level and compared with previous studies in the area. High-resolution sampling of the early Carboniferous at Chestnut Ridge revealed new first appearance datums (FAD) for Bactrognathus and Pseudopolygnathus multistriatus in the Upper Tournaisian (Tn3-Osagean) stage. These new FADs for Bactrognathus and Pseudopolygnathus multistriatus could potentially redefine the lower boundary of the Bactrognathus-Pseudopolygnathus multistriatus Zone at the Chestnut Ridge section.

Future work on this project will involve resampling intervals with little to no yield in conodont elements, as well as continuing sampling into the Elsey Formation. Additionally, conodont samples will be analyzed to create a high-resolution δ¹⁸O curve in order to better understand climatic changes at the Tn2-Tn3 boundary and the resulting implications for regional tectonic processes.