Hayden Quarry, Ghost Ranch (site 2) (Triassic of the United States)

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)."

• bed-level stratigraphic resolution

Environment/lithology: coarse channel fill; gypsiferous, intraclastic, brown, yellow, sandy conglomerate and gray, green siltstone

• "repeated transient flooding events concentrated vertebrate (bones, carcasses, live animals) and plant material from the landscape surface, possibly in hyperconcentrated flows. These events were separated by periods of standing water and weakly-developed, poorly-drained (hydromorphic) soil formation. The hydromorphic nature of the paleosols is evidenced by the drab matrix colorations, abundance of yellow-brown (goethite) mottles, preservation of organic matter, including local leaf litter, predominance of goethite rhizocretions, and general dearth of other redoximorphic features. The high density of channel deposits incised into overbank sediments in the Petrified Forest Member indicate that avulsions were common on the Late Triassic landscape of the Chama Basin, and therefore that the Petrified Forest Member fluvial systems were unstable in this area. This large-scale instability in the local base level and resulting incision has also been reported for the Petrified Forest Member in northern Arizona"
• "The HQ deposits are contained within fossiliferous mudstones, siltstones, and sandy conglomerates that form channel deposits incised into red overbank mudstones and siltstones. The conglomerates are poorly sorted, range in color from brown to yellow and are dominated by intraformational carbonate clasts ranging in size from coarse sand to pebbles. Clasts of permineralized wood and rarer presumed charcoal are commonly found in association with vertebrate remains. Diagenetic gypsum and calcite spar is common. The conglomerates alternate with finer layers of green to pale grey mudstone and siltstone that often include root traces and other organics, but do not show any large-scale evidence of oxidation."

Size class: macrofossils

Collected by Nesbitt, Smith et. al. in 2006-

Collection methods: quarrying, mechanical,

• GR: Ghost Ranch Ruth Hall Museum of Paleontology

Primary reference: S. J. Nesbitt, N. D. Smith, R. B. Irmis, A. H. Turner, A. Downs and M. A. Norell. 2009. A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs. Science 326:1530-1533 [R. Butler/R. Butler]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 92938: authorized by Richard Butler, entered by Richard Butler on 11.12.2009

Creative Commons license: CC BY (attribution)

Taxonomic list

Show authors, comments, and common names
Reptilia
 Loricata - Rauisuchidae
Vivaron haydeni n. gen. n. sp.
Vivaron haydeni n. gen. n. sp. Lessner et al. 2016 rauisuchid
GR 263 (holotype), GR 186, GR 391, GR 639, and GR 640
 Theropoda -
Tawa hallae n. gen. n. sp.
Tawa hallae n. gen. n. sp. Nesbitt et al. 2009 theropod
GR 241, nearly complete associated but disarticulated skull and postcranial skeleton (holotype). Paratypes: GR 242, nearly complete skeleton; GR 155, femora, pelvis and tail; GR 243, cervical vertebrae. Additional undescribed material