New Mexico Geological Society Annual Spring Meeting — Abstracts

Prolific quarries in Arizona have produced extensive collections ofLate Triassic (late Carnian) tetrapods. These quanies include numerous vertebrate collections from the Blue Mesa Member of the Petrified Forest Formation in the Petrified Forest National Park (PFNP), such as "Dying Grounds," "Crocodile Hill," "Wizard Wash" and many others. The other famous late Carnian quarry in Arizona is the Placerias quarry south of St. Johns, Arizona, long thought to be correlative to the PFNP quarries. Recent lithostratigraphic work in western New Mexico and eastern Arizona indicates instead that these localities are separated by as much as 100 m of stratigraphic section, even though they produce nearly identical fossils, including the phytosaur Rutiodon, the metoposaur Buettneria, the aetosaurs Stagonolepis and Desmatosuchus and the dicynodont Placerias. Stagonolepis and Rutiodon are index fossils of Adarnanian land-vertebrate faunachron, which is of latest Carnian age. This lithostratigraphic succession indicates that biostratigraphic subdivision of the Adamanian remains elusive as all common tetrapod taxa occur throughout the section.

The Shinarump Formation is generally assigned an Otischalkian (late Carnian) age based on palynology and the metoposaurid amphibian Buenneria, which is common in strata of late Carnian age. The Bluewater Creek Formation and the Blue Mesa Member in Arizona have produced a diverse fauna of Adamanian (latest Carnian) age. In New Mexico the Blue Mesa is relatively unfossiliferous, but the Bluewater Creek Formation produces and Adamanian fauna consisting of cf. Rutiodon, Stagonolepis, Desmatosuchus, and Buenneria near Fort Wingate. An occurrence of the aetosaur Paratypothorax low in the Bluewater Creek Formation extends the range of that taxon into the early Adamanian.

Two late Triassic microvertebrate localities are known from this outcrop belt, the Placerias quarry and the Fort Wingate Dinosaur site. Litho-and biostratigraphic evidence indicates that both of these quarries lie at or near the base of the Bluewater Creek Formation, and thus are of equivalent age. Both quarries produce dinosaurs, with the Fort Wingate Dinosaur quarry producing extensive fossils of at least two dinosaurs and numerous other previously undescribed taxa.