Improved conodont biostratigraphic constraint of the Carboniferous/Permian boundary in south-central New Mexico, USA

摘要

Recovery of Pi elements of Streptognathodus isolatus and associated nodose streptognathodids from the Laborcita Member of the Bursum Formation near Tularosa, New Mexico clarifies placement of the Carboniferous/Permian boundary in the northern Sacramento Mountains. Conodont elements, fish teeth, and dermal plates are abundant in a thin (4.8 m) highstand carbonate succession located approximately 70 m above the base of the 130 m-thick Laborcita Member. The fauna represents the oldest Permian conodonts discovered thus far in New Mexico and in a basin associated with the Ancestral Rocky Mountains orogen. The occurrence of S. isolatus in this tectonic and geographic setting further demonstrates its utility in defining and correlating the base of the Permian System on a global scale. Occurring with S. isolatus in earliest Asselian strata is S. barricki n. sp., which is described herein.