LOOKING FOR PERMIAN CONODONTS IN A DOMINANTLY RED-BED SUCCESSION IN SE UTAH

The red-bed succession in the vicinity of Valley of the Gods, San Juan County, SE Utah provides beautiful scenery, but would not normally be a destination of choice for research by a Permian conodont worker. This Cutler Group succession was deposited during the Late Carboniferous to Early Permian and is well-known for its vertebrate fossils and providing an archive of environmental change during the late Paleozoic Ice Age. The Geologic Time Scale is a marine scale, but the ultimate goal is to integrate continental successions. Fortunately, a number of thin carbonate units occur episodically, recording major sea-level flooding surfaces that provide a means to integrate timing of marine and continental deposition. Many of these carbonates are sandy and only a few are bioclastic with echinoids and small crinoid ossicles. To date some samples have been barren save for a variety of fish teeth, scales, and centra, but others have yielded conodonts. Conodonts mostly include long-ranging forms that are not normally used for biostratigraphy including Ellisonia, Hindeodus, and Adetognathus. I previously developed a zonal scheme for Adetognathus in the Canadian Arctic that has proven useful in Nevada and Utah, demonstrating that the zonation is inter-regionally valid. This zonation is based on a succession of species including Adetognathus sp. A (now A. flexus; Gzhelian), Adetognathus sp. B (now A. trexleri; upper Gzhelian-lower Asselian), Adetognathus sp. C (still unnamed; mid-upper Asselian), and Adetognathus paralautus (upper Asselian-lower Sakmarian). These taxa exhibit ranges of 3 to 4.5 million years, which is typical for specialized shallow-water species. It is hoped that strontium isotopic analyses might provide addition resolution. The occurrence of A. trexleri in the ‘A’ limestone (Huttenlocker et al., 2020 Lethaia) indicates proximity to the Carboniferous-Permian boundary, but does not indicate with certainty that it is Permian. Samples yielding species of Streptognathodus are needed to provide sufficient resolution given that the Gzhelian-Asselian interval includes up to 14 biozones. One sample to date includes species of Streptognathodus that indicate an early Asselian age, but there are also a few reworked specimens. Samples collected in May 2023 hopefully will provide material that confirm the Permian.