Where: Rio Arriba County, New Mexico (36.3° N, 106.5° W: paleocoordinates 11.5° N, 45.4° W)
• coordinate based on nearby landmark
• outcrop-level geographic resolution
When: Petrified Forest Member (Chinle Formation), Norian (228.0 - 208.5 Ma)
• lower part of the member; "The Hayden Quarry has been dated to ~215 to 213 million years ago."
•"Determining absolute ages of the Chinle Formation is difficult because of a lack of available radiometric dates and comprehensive paleomagnetic records. The best age estimates come from palynological and vertebrate biostratigraphy. Litwin and his colleagues (1986; Litwin et al. 1991) described Norian-aged palynological assemblages from the approximate level of the Canjilon Quarry, and assemblages from the overlying “upper siltstone” member (which contains the Coelophysis Quarry) that are no older than mid-Norian in age. The HQ assemblage includes several biostratigraphically useful vertebrate taxa: pseudopalatine phytosaurs, and the aetosaurs Typothorax coccinarum and Rioarribasuchus chamaensis. These taxa are only found in sediments with Norian pollen at Petrified Forest National Park (PEFO), Arizona and other Chinle Formation localities. Furthermore, pseudopalatine phytosaurs and Typothorax are found both above and below the Black Forest Tuff at PEFO, a local marker bed that yielded the only published radiometric date in the Chinle Formation. Detrital zircons from the Black Forest Tuff indicate a maximum 206Pb/238U age of 213 Ma (Riggs et al. 2003). The association of vertebrate taxa found at this stratigraphic level has a longer range both above and below the Black Forest Tuff, so it is not clear what part of this range correlates with the HQ assemblage. Nonetheless, a broadly Norian age for the HQ assemblage is justified because both the vertebrates and pollen provide an unambiguous Norian signal, and there is at present no evidence to the contrary. This age assignment is also consistent with preliminary results from magnetostratigraphy in the Chama Basin (Zeigler et al. 2005)."
• group of beds-level stratigraphic resolution
Environment/lithology: coarse channel fill; gypsiferous, intraclastic, brown, yellow, sandy conglomerate and gray, green siltstone
Size class: macrofossils
Collected by Irmis, Nesbitt, Turner, et. al. in 2006-
Collection methods: quarrying, mechanical,
Primary reference: R. B. Irmis, S. J. Nesbitt, K. Padian, N. D. Smith, A. H. Turner, D. T. Woody, and A. Downs. 2007. A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs. Science 317:358-361 [M. Carrano/M. Carrano]more details
Purpose of describing collection: taxonomic analysis
PaleoDB collection 74202: authorized by Matthew Carrano, entered by Matthew Carrano on 30.07.2007, edited by Richard Butler and Bethany Allen
Creative Commons license: CC BY (attribution)