Bull Canyon Formation
{{Short description|Geological formation in New Mexico and Texas, US}}
{{Infobox rockunit
| name = Bull Canyon Formation
| image =
| caption =
| type = Geological formation
| age = {{Geological range|Norian|Norian|Upper Triassic, late Norian}}
| period = Norian
| prilithology = mudstone
| otherlithology = sandstone, siltstone, conglomerate
| namedfor = Bull Canyon (Guadalupe County, New Mexico)
| namedby = Lucas & Hunt, 1989
| region = {{Flag|New Mexico}},
{{Flag|Texas}}
| country = {{Flag|United States}}
| coordinates =
| unitof = Dockum Group
| subunits =
| underlies = Redonda Formation
| overlies = Trujillo Formation
| thickness = {{Convert|110|m|ft}}
| extent =
| area =
| map =
| map_caption =
}}
The Bull Canyon Formation is a geological formation of Late Triassic (Norian) age in eastern New Mexico and the Texas Panhandle. It is one of several formations encompassed by the Dockum Group.
The Bull Canyon Formation preserves reptile fossils of the Revueltian "faunachron", and it is generally considered time-equivalent to the upper Cooper Canyon Formation, which crops out further south in west-central Texas.
History and geology
Triassic rocks in the Tucumcari Basin of east-central New Mexico have been prospected for fossils since the 1890s. The bulk of early fossil collecting in the formation was done by University of Michigan paleontologist E.C. Case (starting in the 1910s) and Yale paleontologist Joseph T. Gregory (starting in the 1940s). For much of the 20th century, all Late Triassic strata in New Mexico was assumed to belong to the Chinle Formation.{{Cite journal |last=Hunt |first=Adrian P. |date=1997 |title=E.C. Case, J.T. Gregory, and early exploration for fossil vertebrates in the Bull Canyon Formation (Upper Triassic) of Eastern New Mexico |url=https://books.google.com/books?id=YWcdCgAAQBAJ&pg=PA15 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=11 |pages=15–24}} Kelley (1972) informally labelled a unit of fine-grained sediments in the upper part of the Triassic strata as the "upper shale member" of the Chinle Formation.{{Cite journal |last=Kelley |first=Vincent C. |date=1972 |editor-last=Kelley |editor-first=V. C. |editor2-last=Trauger |editor2-first=F. D. |title=Triassic rocks of the Santa Rosa country |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/23/23_p0084_p0090.pdf |journal=New Mexico Geological Society 23rd Annual Fall Field Conference Guidebook |language=en |publisher=New Mexico Geological Society |pages=84–90 |doi=10.56577/FFC-23}}{{Cite journal |last1=Lucas |first1=Spencer G. |last2=Hunt |first2=Adrian P. |last3=Morales |first3=Michael |date=1985 |title=Stratigraphic nomenclature and correlation of Triassic rocks of east-central New Mexico--A preliminary report |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/36/36_p0171_p0184.pdf |journal=New Mexico Geological Society 36th Annual Fall Field Conference Guidebook |language=en |publisher=New Mexico Geological Society |pages=171–184 |doi=10.56577/FFC-36.171}}
Lucas & Hunt (1989) introduced the name "Bull Canyon Formation" for these exposures, referring to an area of badlands near Luciano Mesa in eastern Guadalupe County, New Mexico. At the Bull Canyon badlands (the type locality), the formation preserves {{Convert|95|m|ft}} of sediment, about 80% of which is dark reddish mudstone. Yellowish-grey or greyish-red fine quartzarenite sandstone makes up about 16% of the layers, with rare siltstone and siltstone-pebble conglomerate.{{Cite journal |last1=Lucas |first1=Spencer G. |last2=Hunt |first2=Adrian P. |date=1989 |editor-last=Lucas |editor-first=Spencer G. |editor2-last=Hunt |editor2-first=Adrian P. |title=Revised Triassic stratigraphy in the Tucumcari Basin, east-central New Mexico |url=https://books.google.com/books?id=Ar1hCgAAQBAJ&pg=PA150 |journal=Dawn of the Age of Dinosaurs in the American Southwest |publisher=New Mexico Museum of Natural History |pages=150–170}} Of special note is a thick brownish litharenite sandstone bed, the Saladito Point Bed, which is comparable to some sandstone beds in Petrified Forest National Park, Arizona. The Bull Canyon Formation reaches a maximum thickness of {{Convert|110|m|ft}} in eastern New Mexico.{{Cite journal |last=Lucas |first=Spencer G. |last2=Heckert |first2=Andrew B. |last3=Hunt |first3=Adrian P. |date=2001 |title=Triassic stratigraphy, biostratigraphy and correlation in east-central New Mexico |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/52/52_p0085_p0102.pdf |journal=New Mexico Geological Society 52nd Annual Fall Field Conference Guidebook |language=en |publisher=New Mexico Geological Society |pages=85–102 |doi=10.56577/FFC-52.85 |isbn=978-1-58546-087-8}} It lies above the Trujillo Formation, which has a much greater proportion of sandstone beds. In New Mexico, the Bull Canyon Formation is overlain by a similar but generally finer-grained geological unit, the Redonda Formation.
= Relationship to the Cooper Canyon Formation =
For much of the 1990s and 2000s, the Bull Canyon Formation was conflated with another geological unit in the Dockum Group: the Cooper Canyon Formation. The Cooper Canyon Formation, which is most well-exposed in Garza County, Texas, was initially named as the "Cooper Member" by Chatterjee (1986),{{Cite book |last1=Chatterjee |first1=Sankar |title=The Beginning of the Age of Dinosaurs: Faunal change across the Triassic-Jurassic boundary |last2=Carpenter |first2=Kenneth |publisher=Cambridge University Press |year=1986 |isbn=0521303281 |editor-last=Padian |editor-first=Kevin |location=New York |pages=139–150 |chapter=The Late Triassic Dockum vertebrates: their stratigraphic and paleobiogeographic significance |chapter-url=https://archive.org/details/beginningofageof0000unse/page/138/mode/2up}} before being raised to formation status by Lehman et al. (1992).{{Cite journal |last1=Lehman |first1=Thomas |last2=Chatterjee |first2=Sankar |last3=Schnable |first3=John |date=1992 |title=The Cooper Canyon Formation (Late Triassic) of western Texas |url=https://www.thefreelibrary.com/The+Cooper+Canyon+Formation+(Late+Triassic)+of+western+Texas.-a0128663777 |journal=Texas Journal of Science |volume=44 |pages=349–355}} Both formations are thick geological units with a large proportion of reddish mudstone. Lehman et al. (1992) and Lehman (1994){{cite journal |last1=Lehman |first1=Thomas M. |year=1994 |title=The saga of the Dockum Group and the case of the Texas/New Mexico boundary fault |url=https://geoinfo.nmt.edu/publications/monographs/bulletins/downloads/150/B150.pdf#page=37 |journal=New Mexico Bureau of Mines & Mineral Resources Bulletin |volume=150 |pages=37–51 |accessdate=}} argued that the Bull Canyon Formation should be synonymized with the Cooper Canyon Formation. These authors suggested that the Boren Ranch Sandstone, which underlies the Cooper Canyon Formation in Garza County, is equivalent to the sandstone-rich Trujillo Formation in New Mexico and the Texas Panhandle. If this is the case, then the "Cooper Member" (and consequently Cooper Canyon Formation) would take priority as the first formal name applied to the mudstone-rich strata above the Trujillo Formation.
Lucas and his colleagues pushed back, arguing that the "Cooper Member" was an invalid name: Chatterjee (1986)'s original stratotype was too thin to be comparable with other areas, and "Cooper" was preoccupied by Cooper Marl of South Carolina. They favored the Bull Canyon Formation as the first valid formal name for the mudstone-rich strata.{{cite journal |last1=Lucas |first1=Spencer G. |last2=Anderson |first2=Orin J. |last3=Hunt |first3=Adrian P. |year=1994 |title=Triassic stratigraphy and correlations, southern High Plains of New Mexico—Texas |url=https://geoinfo.nmt.edu/publications/monographs/bulletins/downloads/150/B150.pdf#page=105 |journal=New Mexico Bureau of Mines & Mineral Resources Bulletin |volume=150 |pages=105–126 |accessdate=}} Carpenter (1997) reviewed both perspectives, noting various cases of noncompliance with the North American Stratigraphic Code. Carpenter eventually sided with Lehman's perspective.{{Cite journal |last=Carpenter |first=Kenneth |date=1997-08-13 |title=A Giant Coelophysoid (Ceratosauria) Theropod from the Upper Triassic of New Mexico, USA |url=https://www.researchgate.net/publication/287004648 |journal=Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen |language=en |volume=205 |issue=2 |pages=189–208 |doi=10.1127/njgpa/205/1997/189 |issn=0077-7749}} Despite the disagreement between these two schools of thought, most studies agreed that the two formations, as generally perceived, were probably one-to-one equivalents.
More extensive geological mapping in Texas by Martz (2008) disagreed with the idea that the Bull Canyon and Cooper Canyon formations were exact equivalents, nullifying the debate over priority. Martz notes that the sandstone beds of the Trujillo Formation are not equivalent to the Boren Ranch Sandstone, but rather to the middle part of the Cooper Canyon Formation. This would indicate that the lower-middle part of the Cooper Canyon Formation is older than the Bull Canyon Formation, and that only the upper Cooper Canyon Formation is equivalent.{{cite thesis |last1=Martz |first1=J. W. |year=2008 |title=Lithostratigraphy, chemostratigraphy, and vertebrate biostratigraphy of the Dockum Group (Upper Triassic), of southern Garza County, West Texas |type=Unpublished PhD thesis |publisher=Texas Tech University |url=https://ttu-ir.tdl.org/handle/2346/20495 |access-date=16 November 2021}}
Paleobiota
{{paleobiota-key-compact}}Several microvertebrate assemblages are known from the Bull Canyon Formation.{{Cite journal |last1=Lucas |first1=Spencer G. |last2=Oakes |first2=Wayne |last3=Froehlich |first3=Jeffery W. |date=1985 |title=Triassic microvertebrate locality, Chinle Formation, east-central New Mexico |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/36/36_p0205_p0212.pdf |journal=New Mexico Geological Society 36th Annual Fall Field Conference Guidebook |language=en |publisher=New Mexico Geological Society |pages=205–212 |doi=10.56577/FFC-36.205}}{{Cite journal |last1=Hunt |first1=Adrian P. |last2=Lucas |first2=Spencer G. |date=1993 |title=Late Triassic microvertebrate localities in New Mexico (USA): implications for paleoecology |url=https://books.google.com/books?id=qbP9CQAAQBAJ&pg=PA187 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=3 |pages=187–192}}{{Cite journal |last=Heckert |first=Andrew B. |date=2004 |title=Upper Triassic microvertebrates from the lower Chinle Group: Introduction, methods, and previous studies |url=https://books.google.com/books?id=T2cfCgAAQBAJ&pg=PA3 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=27 |pages=3–11}}{{Cite journal |last1=Heckert |first1=Andrew B. |last2=Lucas |first2=Spencer G. |date=2006 |title=Micro- and small vertebrate biostratigraphy and biochronology of the Upper Triassic Chinle Group, southwestern USA |url=https://books.google.com/books?id=ulvmCQAAQBAJ&pg=PA94 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=37 |pages=94–104}}
= Temnospondyls =
| class="wikitable" align="center"
! colspan="6" align="center" |Temnospondyls of the Bull Canyon Formation |
| Genus / Taxon
!Species !Locality !Material !Notes !Images |
|---|
| style="background:#E6E6E6;" |Apachesaurus
|style="background:#E6E6E6;" |A. gregorii |style="background:#E6E6E6;" | Bull Canyon, |style="background:#E6E6E6;" |Skull, intercentra, other possible fragments |style="background:#E6E6E6;" |A small metoposaurid which appears to be better suited for terrestrial life than other metoposaurids. Apachesaurus may simply represent juveniles of larger metoposaurids native to the American Southwest.{{Cite journal |last1=Gee |first1=Bryan M. |last2=Parker |first2=William G. |date=2020-02-07 |title=Morphological and histological description of small metoposaurids from Petrified Forest National Park, AZ, USA and the taxonomy of Apachesaurus |url=https://web.archive.org/web/20200710105407id_/https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1199&context=natlpark |journal=Historical Biology |language=en |volume=32 |issue=2 |pages=203–233 |doi=10.1080/08912963.2018.1480616 |bibcode=2020HBio...32..203G |issn=0891-2963}} |style="background:#E6E6E6;" |File:Apachesaurus1DB.jpg |
| Metoposauridae indet.
| | |Large metoposaurid fragments of uncertain affinities, most common in conglomerates in the lower part of the formation. Possibly reworked from older strata. | |
= Synapsids =
| class="wikitable" align="center"
! colspan="6" align="center" |Synapsids of the Bull Canyon Formation |
| Genus / Taxon
!Species !Locality !Material !Notes !Images |
|---|
| Pseudotriconodon{{Cite journal |last1=Lucas |first1=Spencer G. |last2=Oakes |first2=Wayne |date=1988 |title=A Late Triassic cynodont from the American South-West |url=https://www.palass.org/sites/default/files/media/publications/palaeontology/volume_31/vol31_part2_pp445-449.pdf |journal=Palaeontology |volume=31 |issue=2 |pages=445–449}}
|Teeth |A "dromatheriid" cynodont. | |
= Reptiles =
== Avemetatarsalians ==
== Phytosaurs ==
== Other pseudosuchians ==
== Other reptiles ==
= Fish =
Scales, coprolites, and other fragmentary fish fossils are common in the Bull Canyon and Revuelto Creek areas. Most of these likely belong to actinopterygians.
= Other fossils =
The Bull Canyon Formation preserves a rather diverse fauna of freshwater mollusks. Unionid bivalves (freshwater mussels) are locally abundant, primarily Unio (U. arizonensis and at least six unnamed species) and Antediplodon (A. dockumensis and one unnamed species). A hydrobiid snail, Triasamnicola pilsbryi, is also common.{{Cite journal |last=Kues |first=Barry S. |date=1985 |title=Nonmarine molluscs from the Chinle Formation, Dockum Group (Upper Triassic), of Bull Canyon, Guadalupe County, New Mexico |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/36/36_p0185_p0196.pdf |journal=New Mexico Geological Society 36th Annual Fall Field Conference Guidebook |language=en |publisher=New Mexico Geological Society |pages=185–196 |doi=10.56577/FFC-36.185}} Ostracods and coiled Spirorbis-like structures (probably tiny snail shells) round out the invertebrate body fossils known from the formation.
Trackways of both vertebrates and invertebrates are known to occur in the Bull Canyon Formation. Narrow Acripes tracks were probably emplaced by notostracan crustaceans (tadpole shrimp) crawling in shallow temporary pools. A vertebrate ichnotaxon, Barrancapus cresapi, was named for vertebrate footprints found near Barranca Creek.{{Cite journal |last1=Hunt |first1=Adrian P. |last2=Lockley |first2=Martin G. |last3=Lucas |first3=Spencer G. |date=1993 |title=Vertebrate and invertebrate tracks and trackways from the Upper Triassic strata of the Tucumcari Basin, East-Central New Mexico, USA |url=https://books.google.com/books?id=qbP9CQAAQBAJ&pg=PA199 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=3 |pages=199–201}}
A few plant fossils have been found in the formation, including charophyte green algae, bennettitalean leaves (Zamites powellii), large horsetail stems (Neocalamites sp.), and foliage of an enigmatic shrubby plant (Sanmiguelia sp.). Root casts and fossil wood are not uncommon, sometimes showing signs of fungus damage.
See also
References
{{reflist}}
External links
- [https://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=NMTRb%3B0 Bull Canyon Formation of Chinle Group] by USGS
Category:Triassic formations of New Mexico