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| [[Sonsela Member]]|| [[Poleo Formation]]|| [[Moss Back Member]]
| [[Sonsela Member]]|| [[Poleo Formation]]|| [[Moss Back Member]]
|-
|-
| [[Blue Mesa Member]]|| rowspan="2" |[[Salitral Formation]]|| rowspan="2" | [[Monitor Butte Member]]
| [[Blue Mesa Member]]
⚫
[[Bluewater Creek Formation]] (NM)
|[[Salitral Formation]]|| [[Monitor Butte Member]]
[[Cameron Member]]
[[Cameron Member]]
| rowspan="3" |"mottled member"
| rowspan="2" |"mottled member"
[[Gartra Member]]
[[Gartra Member]]
|-
⚫
| [[Bluewater Creek Formation]] (NM)
|-
|-
|[[Mesa Redondo Member]]
|[[Mesa Redondo Member]]
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[[File:Quartz-permineralized fossil wood (Chinle Formation, Upper Triassic; Petrified Forest, Arizona, USA) 1 (49004642997).jpg|thumb|[[Fossil wood]] from Chinle Formation exposures at Petrified Forest National Park ]]Some of the most extensive deposits of the Chinle Formation are found in the southern Colorado Plateau, including Arizona and the western portion of New Mexico. In this region, the oldest and stratigraphically lowest portion of the Chinle is the '''[[Shinarump Conglomerate]]'''. The Shinarump includes braided-river system channel-deposit [[facies]].<ref name="dubiel89" /> The Shinarump interfingers with a finer-grained subunit, the '''[[Mesa Redondo Member]]''', one of the oldest widespread units in the badlands of the [[Painted Desert (Arizona)|Painted Desert]] area. In western New Mexico (particularly the [[Zuñi Mountains|Zuni Mountains]] area), the Mesa Redondo Member may be replaced by another sandy unit known as the '''[[Zuni Mountains Formation]]'''. Sediments from this time interval are followed by a geological unit called the '''[[Bluewater Creek Formation]]'''.<ref name="lucas-hayden-1989" />
[[File:Quartz-permineralized fossil wood (Chinle Formation, Upper Triassic; Petrified Forest, Arizona, USA) 1 (49004642997).jpg|thumb|[[Fossil wood]] from Chinle Formation exposures at Petrified Forest National Park ]]Some of the most extensive deposits of the Chinle Formation are found in the southern Colorado Plateau, including Arizona and the western portion of New Mexico. In this region, the oldest and stratigraphically lowest portion of the Chinle is the '''[[Shinarump Conglomerate]]'''. The Shinarump includes braided-river system channel-deposit [[facies]].<ref name="dubiel89" /> The Shinarump interfingers with a finer-grained subunit, the '''[[Mesa Redondo Member]]''', one of the oldest widespread units in the badlands of the [[Painted Desert (Arizona)|Painted Desert]] area. In western New Mexico (particularly the [[Zuñi Mountains|Zuni Mountains]] area), the Mesa Redondo Member may be replaced by another sandy unit known as the '''[[Zuni Mountains Formation]]'''. Sediments from this time interval are followed by a geological unit called the '''[[Bluewater Creek Formation]]'''.<ref name="lucas-hayden-1989" />


Most Chinle outcrops in the Painted Desert have traditionally been placed within the following '''[[Petrified Forest Member]]''', a segment of Triassic sediments which are so diverse and extensive that it is sometimes raised to its own formation, subdivided further, or redefined more narrowly. In its widest definition, the Petrified Forest Member (or Formation) is split into three sections: the muddy Lower Petrified Forest and Upper Petrified Forest, and the sandy Sonsela Sandstone bed, which separates them. The Lower "Petrified Forest Member" is generally known as the '''[[Blue Mesa Member]]'''.<ref name=":0">{{Cite book |last=Woody |first=Daniel T. |url= |title=A century of research at Petrified Forest National Park : geology and paleontology |date=2006 |publisher=Museum of Northern Arizona |isbn=0-89734-120-1 |editor-last=Parker |editor-first=W.G. |chapter=Revised stratigraphy of the Lower Chinle Formation (Upper Triassic) of Petrified Forest National Park, Arizona |oclc=71015548 |editor-last2=Ash |editor-first2=S.R. |editor-last3=Irmis |editor-first3=R.B. |chapter-url=https://www.ldeo.columbia.edu/~polsen/cpcp/woody_06.pdf}}</ref> In [[Petrified Forest National Park]] and its vicinities, the Sonsela Sandstone is thick enough that it can be resolved into several distinct sandstone-rich layers. It is renamed as the '''[[Sonsela Member]]''' in this situation.<ref name=":0" /> The Sonsela Sandstone is a collection of braided-stream channel facies.<ref>{{Cite journal |last=Martz |first=Jeffrey W. |last2=Parker |first2=William G. |date=2010-02-19 |title=Revised Lithostratigraphy of the Sonsela Member (Chinle Formation, Upper Triassic) in the Southern Part of Petrified Forest National Park, Arizona |url=https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0009329 |journal=PLOS ONE |language=en |volume=5 |issue=2 |pages=e9329 |doi=10.1371/journal.pone.0009329 |issn=1932-6203 |pmc=2824835 |pmid=20174475}}</ref> The Upper "Petrified Forest Member" is sometimes called the Painted Desert Member,<ref name="lucas-2020">{{cite journal |last1=Lucas |first1=Spencer G. |title=Triassic stratigraphy of the southeastern Colorado Plateau, west-central New Mexico |journal=New Mexico Geological Society Special Publication |date=2020 |volume=14 |pages=123–133 |url=https://nmgs.nmt.edu/publications/special/14/NMGS_SP-14.pdf |access-date=30 October 2020}}</ref> or simply referred to as the Petrified Forest Member in a more restricted definition of the term.<ref name=":0" /> The Petrified Forest is predominately overbank deposits with thin lenses of channel-deposit facies and lacustrine deposits.
Most Chinle outcrops in the Painted Desert have traditionally been placed within the following '''[[Petrified Forest Member]]''', a segment of Triassic sediments which are so diverse and extensive that it is sometimes raised to its own formation, subdivided further, or redefined more narrowly. In its widest definition, the Petrified Forest Member (or Formation) is split into three sections: the muddy Lower Petrified Forest and Upper Petrified Forest, and the sandy Sonsela Sandstone bed, which separates them. The Lower "Petrified Forest Member" is generally known as the '''[[Blue Mesa Member]]'''.<ref name=":0">{{Cite book |last=Woody |first=Daniel T. |url= |title=A century of research at Petrified Forest National Park : geology and paleontology |date=2006 |publisher=Museum of Northern Arizona |isbn=0-89734-120-1 |editor-last=Parker |editor-first=W.G. |chapter=Revised stratigraphy of the Lower Chinle Formation (Upper Triassic) of Petrified Forest National Park, Arizona |oclc=71015548 |editor-last2=Ash |editor-first2=S.R. |editor-last3=Irmis |editor-first3=R.B. |chapter-url=https://www.ldeo.columbia.edu/~polsen/cpcp/woody_06.pdf}}</ref> In [[Petrified Forest National Park]] (PEFO) and its vicinities, the Sonsela Sandstone is thick enough that it can be resolved into several distinct sandstone-rich layers. It is renamed as the '''[[Sonsela Member]]''' in this situation.<ref name=":0" /> The Sonsela Sandstone is a collection of braided-stream channel facies.<ref>{{Cite journal |last=Martz |first=Jeffrey W. |last2=Parker |first2=William G. |date=2010-02-19 |title=Revised Lithostratigraphy of the Sonsela Member (Chinle Formation, Upper Triassic) in the Southern Part of Petrified Forest National Park, Arizona |url=https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0009329 |journal=PLOS ONE |language=en |volume=5 |issue=2 |pages=e9329 |doi=10.1371/journal.pone.0009329 |issn=1932-6203 |pmc=2824835 |pmid=20174475}}</ref> The Upper "Petrified Forest Member" is sometimes called the Painted Desert Member,<ref name="lucas-2020">{{cite journal |last1=Lucas |first1=Spencer G. |title=Triassic stratigraphy of the southeastern Colorado Plateau, west-central New Mexico |journal=New Mexico Geological Society Special Publication |date=2020 |volume=14 |pages=123–133 |url=https://nmgs.nmt.edu/publications/special/14/NMGS_SP-14.pdf |access-date=30 October 2020}}</ref> or simply referred to as the Petrified Forest Member in a more restricted definition of the term.<ref name=":0" /> The Petrified Forest is predominately overbank deposits with thin lenses of channel-deposit facies and lacustrine deposits.


The Petrified Forest Member grades into the '''[[Owl Rock Member]]''', a marginal lacustrine to lacustrine facies possibly representing a large lake system. The Owl Rock Member is followed by the youngest and sandiest subunit of the Chinle, the '''[[Rock Point Member]]'''. The Rock Point is distinct enough that it was previously considered a unit of the [[Wingate Sandstone]], a latest Triassic - early Jurassic aeolian formation which overlies the Chinle in many areas.<ref name="StewartEtal1972" />
The Petrified Forest Member grades into the '''[[Owl Rock Member]]''', a marginal lacustrine to lacustrine facies possibly representing a large lake system. The Owl Rock Member is followed by the youngest and sandiest subunit of the Chinle, the '''[[Rock Point Member]]'''. The Rock Point is distinct enough that it was previously considered a unit of the [[Wingate Sandstone]], a latest Triassic - early Jurassic aeolian formation which overlies the Chinle in many areas.<ref name="StewartEtal1972" />
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== Chronology ==
== Chronology ==


=== Tetrapod biostratigraphy ===
The Chinle Formation is aged from early [[Late Triassic]]. Age correlation is based on Lucas's [[Land Vertebrate Faunachron]]s. The faunachrons are based on first and last appearances of [[phytosaur]]s. Simplified [[stratigraphy]] based on Litwin.<ref>Litwin, R.J., Traverse, A., and Ash, S.R., 1991. Preliminary palynological zonation of the Chinle Formation, southwestern U.S.A., and its correlation to the Newark Supergroup (eastern U.S.A.). Review of Paleobotany and Palynology, v. 77, pp. 269–287.</ref>
The Chinle Formation is aged from early [[Late Triassic]]. Age correlation is based on Lucas's [[Land Vertebrate Faunachron]]s. The faunachrons are based on first and last appearances of [[phytosaur]]s. Simplified [[stratigraphy]] based on Litwin.<ref>Litwin, R.J., Traverse, A., and Ash, S.R., 1991. Preliminary palynological zonation of the Chinle Formation, southwestern U.S.A., and its correlation to the Newark Supergroup (eastern U.S.A.). Review of Paleobotany and Palynology, v. 77, pp. 269–287.</ref>
{| class="wikitable"
{| class="wikitable"
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| [[Adamanian]]
| [[Adamanian]]
| Sonsela Sandstone
| Sonsela Sandstone
Lower Petrified Forest
Blue Mesa (Lower Petrified Forest)


Moss Back
Moss Back
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Temple Mountain
Temple Mountain
|}
|}

=== Radiometric dating ===
[[Radiometric dating]] has helped to refine precise age data for the Chinle Formation, particularly in areas with a more complete stratigraphic record such as Petrified Forest National Park (PEFO). Volcanism further southwest along the [[Cordilleran magmatic arc]] supplies [[zircon]] crystals to the Chinle system, allowing for [[Uranium–lead dating|U-Pb dating]] of layers which host zircon grains. Eroded sediments from the [[Ouachita Mountains]] and [[Mogollon Highlands]] also supply older reworked zircon in smaller concentrations to the basin.<ref name=":4">{{Cite journal |last=Gehrels |first=George |last2=Giesler |first2=Dominique |last3=Olsen |first3=Paul |last4=Kent |first4=Dennis |last5=Marsh |first5=Adam |last6=Parker |first6=William |last7=Rasmussen |first7=Cornelia |last8=Mundil |first8=Roland |last9=Irmis |first9=Randall |last10=Geissman |first10=John |last11=Lepre |first11=Christopher |date=2020-09-23 |title=LA-ICPMS U–Pb geochronology of detrital zircon grains from the Coconino, Moenkopi, and Chinle formations in the Petrified Forest National Park (Arizona) |url=https://gchron.copernicus.org/articles/2/257/2020/ |journal=Geochronology |language=English |volume=2 |issue=2 |pages=257–282 |doi=10.5194/gchron-2-257-2020}}</ref>

Chinle radiometric dating is complicated by lithological quirks to zircon deposition. U-Pb dates from coarse-grained layers are often several million years older than expected based on magnetostratigraphy, while mud-dominated layers are generally more accurate despite a lower sample size. This is likely because sandy rivers receive a higher proportion of recycled zircon grains from distant eroded rocks, while muddy plains are supplied with fresh zircon-rich ash from contemporary volcanic eruptions. While zircons from sandstone-rich layers are less useful for inferring direct depositional ages, they can be very useful for inferring sediment sources: each igneous or metamorphic sediment source has its own set of old (usually Precambrian) zircon ages, which can be traced in Triassic sediments.<ref name=":4" />

Outcrops of the Mesa Redondo Member at PEFO have been dated to ~225 Ma (2011)<ref name=":5">{{Cite journal |last=Ramezani |first=Jahandar |last2=Hoke |first2=Gregory D. |last3=Fastovsky |first3=David E. |last4=Bowring |first4=Samuel A. |last5=Therrien |first5=François |last6=Dworkin |first6=Steven I. |last7=Atchley |first7=Stacy C. |last8=Nordt |first8=Lee C. |date=2011-11-01 |title=High-precision U-Pb zircon geochronology of the Late Triassic Chinle Formation, Petrified Forest National Park (Arizona, USA): Temporal constraints on the early evolution of dinosaurs |url=https://doi.org/10.1130/B30433.1 |journal=GSA Bulletin |volume=123 |issue=11-12 |pages=2142–2159 |doi=10.1130/B30433.1 |issn=0016-7606}}</ref> or ~228 Ma (2013),<ref>{{Cite journal |last=Atchley |first=Stacy C. |last2=Nordt |first2=Lee C. |last3=Dworkin |first3=Stephen I. |last4=Ramezani |first4=Jahandar |last5=Parker |first5=William G. |last6=Ash |first6=Sidney R. |last7=Bowring |first7=Samuel A. |date=2013-12-01 |title=A Linkage Among Pangean Tectonism, Cyclic Alluviation, Climate Change, and Biologic Turnover In the Late Triassic: The Record From The Chinle Formation, Southwestern United States |url=https://doi.org/10.2110/jsr.2013.89 |journal=Journal of Sedimentary Research |volume=83 |issue=12 |pages=1147–1161 |doi=10.2110/jsr.2013.89 |issn=1527-1404}}</ref> though these may be influenced by recycled grains; later estimates from a major [[Core drill|core drilling]] project suggest a more recent age of 223-222 Ma (2020).<ref name=":6">{{Cite journal |last=Rasmussen |first=Cornelia |last2=Mundil |first2=Roland |last3=Irmis |first3=Randall B. |last4=Geisler |first4=Dominique |last5=Gehrels |first5=George E. |last6=Olsen |first6=Paul E. |last7=Kent |first7=Dennis V. |last8=Lepre |first8=Christopher |last9=Kinney |first9=Sean T. |last10=Geissman |first10=John W. |last11=Parker |first11=William G. |date=2020-07-20 |title=U-Pb zircon geochronology and depositional age models for the Upper Triassic Chinle Formation (Petrified Forest National Park, Arizona, USA): Implications for Late Triassic paleoecological and paleoenvironmental change |url=https://doi.org/10.1130/B35485.1 |journal=GSA Bulletin |volume=133 |issue=3-4 |pages=539–558 |doi=10.1130/B35485.1 |issn=0016-7606}}</ref><ref name=":4" /> This firmly suggests that nearly all of the Chinle Formation was deposited in the Norian, a stage which began around 227 Ma based on tentative assessments of marine strata.<ref name=":3">{{Cite journal |last1=Ogg |first1=James G. |last2=Huang |first2=Chunju |last3=Hinnov |first3=Linda |date=May 2014 |title=Triassic timescale status: a brief overview |url=https://albertiana-sts.org/wp-content/uploads/2017/06/Albertiana_41.pdf#page=5 |journal=Albertiana |volume=41 |pages=3–30}}</ref>

At PEFO, U-Pb estimates from the Blue Mesa Member include 223 Ma (2011),<ref name=":5" /> 222 Ma (2020),<ref name=":6" /> and 221-218 Ma (2020).<ref name=":4" /> Outcrops near [[St. Johns, Arizona]] fit this general time period as well. The fossiliferous ''Placerias'' quarry, previously regarded as belonging to an older subunit, is likely part of the Blue Mesa Member based on an age date of 219.4 Ma (2014).<ref>{{Cite journal |last=Ramezani |first=Jahandar |last2=Fastovsky |first2=David E. |last3=Bowring |first3=Samuel A. |date=2014-06-01 |title=Revised chronostratigraphy of the Lower Chinle Formation strata in Arizona and New Mexico (USA): High-precision U-Pb geochronological constraints on the Late Triassic evolution of dinosaurs |url=https://www.ajsonline.org/content/314/6/981 |journal=American Journal of Science |language=en |volume=314 |issue=6 |pages=981–1008 |doi=10.2475/06.2014.01 |issn=0002-9599}}</ref>

Until 2011, all published radiometric age data was restricted to the Black Forest Bed, a sandstone layer near the top of the Petrified Forest Member in PEFO. U-Pb estimates for this layer include ~213 Ma (2003 maximum),<ref>{{Cite journal |last=Riggs |first=N.R. |last2=Ash |first2=S.R. |last3=Barth |first3=A.P. |last4=Gehrels |first4=G.E. |last5=Wooden |first5=J.L. |date=2003-11-01 |title=Isotopic age of the Black Forest Bed, Petrified Forest Member, Chinle Formation, Arizona: An example of dating a continental sandstone |url=https://doi.org/10.1130/B25254.1 |journal=GSA Bulletin |volume=115 |issue=11 |pages=1315–1323 |doi=10.1130/B25254.1 |issn=0016-7606}}</ref> ~211 Ma (2009),<ref>{{Cite journal |last1=Heckert |first1=A.B. |last2=Lucas |first2=S.G. |last3=Dickinson |first3=W.R. |last4=Mortensen |first4=J.K. |date=2009 |title=New ID-TIMS U-Pb ages for Chinle Group strata (Upper Triassic) in New Mexico and Arizona, correlation to the Newark Supergroup, and Implications for the "long Norian" |journal=Geological Society of America Abstracts with Programs |volume=41 |issue=7 |pages=123}}</ref> and ~210 Ma (2011, 2020).<ref name=":5" /><ref name=":6" /><ref name=":4" />


==Places found==
==Places found==

Revision as of 16:31, 16 June 2022

Chinle Formation
Stratigraphic range: Carnian–Rhaetian
Chinle Badlands, Grand Staircase-Escalante National Monument, Utah, US.
TypeGeological formation
Sub-unitssee text
UnderliesWingate Sandstone,
Moenave Formation,
Nugget Sandstone
OverliesMoenkopi Formation or Cutler Group
Lithology
Primaryfluvial mudstone, siltstone, and sandstone
Otherpaleosols
Location
Coordinates36°09′18″N 109°34′44″W / 36.155°N 109.579°W / 36.155; -109.579
RegionColorado Plateau
ExtentUtah
Colorado
New Mexico
Arizona
Nevada
Type section
Named forChinle, AZ
Named byHerbert E. Gregory
Chinle Formation is located in the United States
Chinle Formation
Chinle Formation (the United States)
Chinle Formation is located in Arizona
Chinle Formation
Chinle Formation (Arizona)

Type locality in Arizona

The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In New Mexico, it is often raised to the status of a geological group, the Chinle Group. Some authors have controversially considered the Chinle to be synonymous to the Dockum Group of eastern Colorado and New Mexico, western Texas, the Oklahoma panhandle, and southwestern Kansas. The Chinle is sometimes colloquially named as a formation within the Dockum Group in New Mexico and in Texas. The Chinle Formation is part of the Colorado Plateau, Basin and Range, and the southern section of the Interior Plains.[1]

A probable separate depositional basin within the Chinle is found in northwestern Colorado and northeastern Utah. The southern portion of the Chinle reaches a maximum thickness of a little over 520 meters (1,710 ft). Typically, the Chinle rests unconformably on the Moenkopi Formation.

History of investigation

While colorful Triassic sediments of the Colorado Plateau have been investigated since the 19th century, the Chinle Formation was only formally named and described by Herbert E. Gregory in 1917. It was named for Chinle Valley in Apache County, Arizona, land which is largely within the Navajo Nation. Gregory did not designate a type locality. He split the Chinle into four subunits, labelled A (youngest) to D (oldest). This did not include the underlying Shinarump Conglomerate (named by G. K. Gilbert and Edwin E. Howell in 1875), which he considered a separate formation.[2]

United States Geological Survey geologists and paleontologists continued to map out the Chinle Formation through the 20th century, revising the unnamed subunits of Gregory. A basic stratigraphy of the formation was developed for north-central New Mexico by Wood and Northrop (1946), and stratigraphy in the Four Corners Region was established by the late 1950s. In 1956, Economic geologist Raymond C. Robeck identified and named the Temple Mountain member as the basal-most unit in the area of the San Rafael Swell of Utah. In 1957, John H. Stewart revised the Shinarump Conglomerate and renamed it the Shinarump member of the Chinle formation.

Study of the formation expanded northwards into northern Utah and Colorado, facilitated through papers by Forrest G. Poole and Stewart (1964)[3] and Steve W. Sikich (1965),[4] who named informal local members equivalent to those of Arizona and New Mexico. The complete areal extent of the unit was mapped by R.F. Wilson and Stewart in 1967.[5] Stewart and his colleagues created an expansive overview and revision of the formation in 1972, summarizing previous knowledge on Chinle stratigraphy.[6]

V.C. Kelley assigned more members and revised the unit in 1972.[7] Spencer G. Lucas and S.N. Hayden did the same thing in 1989.[8] The Rock Point Member was assigned by R.F. Dubiel in 1989.[9]

The Chinle was raised to group rank by Lucas in 1993,[10] thus also raising many of the members to formation status. He also included the formations of the Dockum Group of eastern New Mexico and west Texas within the "Chinle Group". This modified nomenclature is controversial; many still retain the Chinle as a formation and separate out the Dockum Group.[11][12] The Dockum was named in 1890, before the Chinle. Lucas also advocated abandoning the name Dolores Formation as a parochial synonym for the Chinle Group.

Overviews of the Chinle were created by Dubiel and others (1992) and Hintze and Axen (1995).[13]

Stratigraphy

The formation members and their thicknesses are highly variable across the Chinle.

Regional stratigraphic subunits of the Chinle Formation
Arizona and western New Mexico North-central New Mexico Monument Valley and southern Utah Colorado and northeast Utah
Rock Point Member "siltstone member" (in part) Church Rock Member "upper member"

"red siltstone member"

"ocher siltstone member" (UT)

Owl Rock Member "siltstone member" (in part)

Petrified Forest Member (in part)

Owl Rock Member

Kane Springs beds (in part)

Petrified Forest Member / Painted Desert Member Petrified Forest Member (in part) Petrified Forest Member

Kane Springs beds (in part)

Sonsela Member Poleo Formation Moss Back Member
Blue Mesa Member

Bluewater Creek Formation (NM)

Salitral Formation Monitor Butte Member

Cameron Member

"mottled member"

Gartra Member

Mesa Redondo Member

Shinarump Conglomerate

Zuni Mountains Formation (NM)

Agua Zarca Sandstone / Shinarump Conglomerate

"mottled strata"

Shinarump Conglomerate

Temple Mountain Member

Arizona and western New Mexico

Fossil wood from Chinle Formation exposures at Petrified Forest National Park

Some of the most extensive deposits of the Chinle Formation are found in the southern Colorado Plateau, including Arizona and the western portion of New Mexico. In this region, the oldest and stratigraphically lowest portion of the Chinle is the Shinarump Conglomerate. The Shinarump includes braided-river system channel-deposit facies.[9] The Shinarump interfingers with a finer-grained subunit, the Mesa Redondo Member, one of the oldest widespread units in the badlands of the Painted Desert area. In western New Mexico (particularly the Zuni Mountains area), the Mesa Redondo Member may be replaced by another sandy unit known as the Zuni Mountains Formation. Sediments from this time interval are followed by a geological unit called the Bluewater Creek Formation.[8]

Most Chinle outcrops in the Painted Desert have traditionally been placed within the following Petrified Forest Member, a segment of Triassic sediments which are so diverse and extensive that it is sometimes raised to its own formation, subdivided further, or redefined more narrowly. In its widest definition, the Petrified Forest Member (or Formation) is split into three sections: the muddy Lower Petrified Forest and Upper Petrified Forest, and the sandy Sonsela Sandstone bed, which separates them. The Lower "Petrified Forest Member" is generally known as the Blue Mesa Member.[14] In Petrified Forest National Park (PEFO) and its vicinities, the Sonsela Sandstone is thick enough that it can be resolved into several distinct sandstone-rich layers. It is renamed as the Sonsela Member in this situation.[14] The Sonsela Sandstone is a collection of braided-stream channel facies.[15] The Upper "Petrified Forest Member" is sometimes called the Painted Desert Member,[16] or simply referred to as the Petrified Forest Member in a more restricted definition of the term.[14] The Petrified Forest is predominately overbank deposits with thin lenses of channel-deposit facies and lacustrine deposits.

The Petrified Forest Member grades into the Owl Rock Member, a marginal lacustrine to lacustrine facies possibly representing a large lake system. The Owl Rock Member is followed by the youngest and sandiest subunit of the Chinle, the Rock Point Member. The Rock Point is distinct enough that it was previously considered a unit of the Wingate Sandstone, a latest Triassic - early Jurassic aeolian formation which overlies the Chinle in many areas.[6]

Central New Mexico

The Whitaker ("Coelophysis") Quarry at Ghost Ranch, preserving the "siltstone member" of the Chinle Formation

Unambiguous exposures of the Chinle Formation extend into central New Mexico, beyond the eastern edge of the Colorado Plateau. Most of these are found in the Chama Basin of north-central New Mexico, particularly several famed paleontological sites at Ghost Ranch near Abiquiu. Minor exposures also occur in the Lucero Uplift west of Albuquerque, as well as other areas along the Rio Grande Rift.[17][6]

As in the Colorado Plateau, the lowest major unit in north-central New Mexico is a sandstone-rich member. This layer, the Agua Zarca Sandstone, is often synonymized with the Shinarump Conglomerate,[18][17][16] though it may be derived from a different erosional source.[12] It is often preceded by a very thin layer of silty mottled strata. This mottled strata is sometimes termed the Zuni Mountains Formation,[18][16] though the application of this term beyond the Zuni Mountains is questionable.[17][12] In the Chama Basin at least, the mottled strata is derived from the eroded and pedogenically modified surface of the Moenkopi Formation.[12]

The coarse lower unit grades into the fine-grained Salitral Formation, which is equivalent to the Blue Mesa Member and Bluewater Creek Formation. Coarse sandstone returns along a sharp contact with the following Poleo Formation, an equivalent of the Sonsela Member.[17] The Poleo Formation grades into the thick colorful sediments of the Petrified Forest Member. Authors which raise this member to a formation subdivide it into the lower Mesa Montosa Member and the upper Painted Desert Member.[18][17] The Petrified Forest Member is fossiliferous in the Chama Basin, with major sites including the Hayden, Canjilon, and Snyder quarries of Ghost Ranch.[19]

The stratigraphically highest unit in north-central New Mexico is the informally-named “siltstone member”. This unit is best exposed at Ghost Ranch, where it has produced the famous Whitaker Quarry, also known as the Coelophysis quarry due to a high concentration of fossils belonging to the theropod dinosaur Coelophysis bauri. The “siltstone member” may be equivalent to the Rock Point Member, and some authors refer to it as such.[18][17][16]

Monument Valley and southern Utah

The Shinarump Conglomerate (top, horizontal layers) as an erosion-resistant cap rock in Monument Valley
Permian through Jurassic stratigraphy of Glen Canyon National Recreation Area in Utah.
From top to bottom: (youngest to oldest)
5 – Rounded tan domes of the Navajo Sandstone,
4 – layered red Kayenta Formation,
3 – cliff-forming, vertically jointed, red Wingate Sandstone,
2 – slope-forming, purplish Chinle Formation, layered, lighter-red Moenkopi Formation
1 – white, layered Cutler Formation sandstone.
Picture from Glen Canyon National Recreation Area, Utah

The Chinle continues northwards into southern Utah and the Four Corners area, though it thins greatly to the northwest. A narrow band of undifferentiated purplish sediments from the lower part of the formation extend into vicinity of St. George. The formation thickens eastward into Zion National Park and Grand Staircase-Escalante National Monument. The Chinle is a prominent component of badlands and outcrops in the various national parks, monuments, and recreation areas of southeast Utah, extending in a discontinuous patchwork up to the San Rafael Swell.[20] The stratigraphic nomenclature used in southern Utah is also utilized in Monument Valley, where the coarse-grained lower members of the Chinle form a caprock for many famous buttes which characterize the valley.[6]

In this region, the stratigraphically lowest unit in the Chinle is usually the Shinarump Conglomerate (or Shinarump Member), which thins northward but is a reliable component of outcrops throughout the region. In several areas, a thin layer of mottled paleosols, the Temple Mountain Member, may be superimposed onto the Shinarump and underlying Moenkopi Formation.[20][21]

The Monitor Butte Member overlies the Shinarump and Temple Mountain members in southeast Utah and Monument Valley. This unit comprises drab and generally fine-grained sediments, equivalent to the Blue Mesa Member and Bluewater Creek Formation found further south.[20] The facies of this interval have been interpreted as overbank (distal floodplain) and lacustrine deposits. At Zion National Park, the Monitor Butte Member is replaced by a thick time-equivalent unit, the Cameron Member, which is also found in the Navajo Nation near its namesake of Cameron, Arizona. The Cameron Member is practically identical to the Blue Mesa Member, and likely represents the same depositional environment along the ancient river system responsible for the Chinle Formation. It is also distinct from the Monitor Butte Member, which has more evaporite deposits and fewer red sandy layers.[10][20]

The drab mudstone of the Monitor Butte and Cameron members are succeeded in a few areas by a thin section of massive conglomeratic sandstone, the Moss Back Member. This member represents sandy river channel deposits and is likely equivalent to part of the Sonsela Member.[20] Elsewhere, the Monitor Butte grades into the Petrified Forest Member, which in Utah includes the thin but geographically extensive Correo Sandstone Bed. The Petrified Forest Member is followed by the Owl Rock Member.[20][8] A unit of drab interbedded coarse and fine sediments, the Kane Springs beds, develops in the Paradox Basin. The Kane Springs beds are river deposits which are likely equivalent to the Owl Rock Member and the upper part of the Petrified Forest Member.[20] Finally, either the Rock Point Member or Church Rock Member overlie the Owl Rock. Some researchers feel that the Church Rock and Rock Point members may be synonymous.[22] They are complex heterolithic units, representing variously braided-river facies, lacustrine, and overbank deposits.

Subunits

Glen Canyon Sandstone over Chinle Formation (Dinosaur National Monument, Utah)
Stratigraphic column of the Hayden Quarry fossil locality atGhost Ranch, NM.
Stratigraphy of Canyonlands N.P., with members of the Chinle Formation

Asterisks (*) indicate usage by the U.S. Geological Survey. Other usages by state geological surveys.

Group rank (alphabetical – rank and formations not recognized by the USGS)[1]

Formation rank (alphabetical – several members not recognized by the USGS):[1]

Chronology

Tetrapod biostratigraphy

The Chinle Formation is aged from early Late Triassic. Age correlation is based on Lucas's Land Vertebrate Faunachrons. The faunachrons are based on first and last appearances of phytosaurs. Simplified stratigraphy based on Litwin.[32]

Sub-stage Faunachron Chinle Member(s)
Late Norian-Rhaetian Apachean Rock Point/Church Rock
Early to Middle Norian Revueltian Owl Rock

Upper Petrified Forest

upper Late Carnian Adamanian Sonsela Sandstone

Blue Mesa (Lower Petrified Forest)

Moss Back

Monitor Butte

lower Late Carnian Otischalkian Shinarump

Temple Mountain

Radiometric dating

Radiometric dating has helped to refine precise age data for the Chinle Formation, particularly in areas with a more complete stratigraphic record such as Petrified Forest National Park (PEFO). Volcanism further southwest along the Cordilleran magmatic arc supplies zircon crystals to the Chinle system, allowing for U-Pb dating of layers which host zircon grains. Eroded sediments from the Ouachita Mountains and Mogollon Highlands also supply older reworked zircon in smaller concentrations to the basin.[33]

Chinle radiometric dating is complicated by lithological quirks to zircon deposition. U-Pb dates from coarse-grained layers are often several million years older than expected based on magnetostratigraphy, while mud-dominated layers are generally more accurate despite a lower sample size. This is likely because sandy rivers receive a higher proportion of recycled zircon grains from distant eroded rocks, while muddy plains are supplied with fresh zircon-rich ash from contemporary volcanic eruptions. While zircons from sandstone-rich layers are less useful for inferring direct depositional ages, they can be very useful for inferring sediment sources: each igneous or metamorphic sediment source has its own set of old (usually Precambrian) zircon ages, which can be traced in Triassic sediments.[33]

Outcrops of the Mesa Redondo Member at PEFO have been dated to ~225 Ma (2011)[34] or ~228 Ma (2013),[35] though these may be influenced by recycled grains; later estimates from a major core drilling project suggest a more recent age of 223-222 Ma (2020).[36][33] This firmly suggests that nearly all of the Chinle Formation was deposited in the Norian, a stage which began around 227 Ma based on tentative assessments of marine strata.[37]

At PEFO, U-Pb estimates from the Blue Mesa Member include 223 Ma (2011),[34] 222 Ma (2020),[36] and 221-218 Ma (2020).[33] Outcrops near St. Johns, Arizona fit this general time period as well. The fossiliferous Placerias quarry, previously regarded as belonging to an older subunit, is likely part of the Blue Mesa Member based on an age date of 219.4 Ma (2014).[38]

Until 2011, all published radiometric age data was restricted to the Black Forest Bed, a sandstone layer near the top of the Petrified Forest Member in PEFO. U-Pb estimates for this layer include ~213 Ma (2003 maximum),[39] ~211 Ma (2009),[40] and ~210 Ma (2011, 2020).[34][36][33]

Places found

Geologic Province:[1]

Rock Point Member
Owl Rock Member
Petrified Forest Member
Mesa Redondo Member
Shinarump Member
Petrified Forest Member
Shinarump Member
upper member
red siltstone member (possibly correlative with Church Rock Member)
local sandstone and conglomerate member
ochre siltstone member
mottled member
Gartra Member
Redonda Formation
Bull Canyon Formation
Trujillo Formation
Garita Creek Formation
San Pedro Arroyo Formation
Shinarump Formation
Church Rock Member
Owl Rock Member
Petrified Forest Member
Moss Back Member
Monitor Butte Member
Shinarump Conglomerate
upper member
red siltstone member (possibly correlative with Church Rock Member)
local sandstone and conglomerate member
ochre siltstone member
mottled member
Gartra Member
Rock Point Member
Owl Rock Member
Petrified Forest Member
Mesa Redondo Member
Shinarump Member
Rock Point Formation
Owl Rock Formation
Petrified Forest Formation
Bluewater Creek/San Pedro Arroyo Formations
Shinarump Conglomerate/Zuni Mountains Formation
Stanaker Member
Gartra Member
Stanaker Member
Gartra Member

Parklands:

Other:

See also

Wikimedia Commons has media related to Chinle Formation.

References

  1. ^ a b c d GEOLEX database entry for Chinle, USGS (viewed 19 March 2006)
  2. ^ Gregory, Herbert E. (1917). Geology of the Navajo country - A reconnaissance of parts of Arizona, New Mexico, and Utah (PDF). United States Geological Survey Professional Papers #93. 161 p.
  3. ^ Poole, F. G.; Stewart, J. H. (1964). "Chinle Formation and Glen Canyon Sandstone in Northeast Utah and Northwest Colorado". Geological Survey Research 1964. U.S. Geol. Survey Prof. Paper. 501-D: 93–104. {{cite journal}}: Cite journal requires |journal= (help)
  4. ^ a b c d e Sikitch, Steve W. (1965). "Upper Triassic stratigraphy in the eastern Uinta Mountains". The Mountain Geologist. 2 (3): 167–172. Retrieved 30 October 2020.
  5. ^ Wilson, Richard F.; Stewart, John H. (1967). "Correlation of Upper Triassic and Triassic Formations between southwestern Utah and southern Nevada". U.S. Geological Survey Bulletin. 1244-D: D1–D20. doi:10.3133/b1244D.
  6. ^ a b c d e f Stewart, J.H.; Poole, F.G.; Wilson, R.F. (1972). "Stratigraphy and origin of the Chinle Formation and related Upper Triassic strata in the Colorado Plateau region, with sections on sedimentary petrology by R.A. Cadigan and conglomerate studies by William Thordarson and H.F. Albee" (PDF). U.S. Geological Survey Professional Paper. 690. doi:10.3133/pp690.
  7. ^ Kelley, V.C. (1972). "Geology of the Fort Sumner sheet, New Mexico" (PDF). New Mexico Bureau of Mines and Mineral Resources Bulletin. 98. Retrieved 30 October 2020.
  8. ^ a b c d e Lucas, S.G.; Hayden, S.N. (1989). "Triassic stratigraphy of west-central New Mexico" (PDF). New Mexico Geological Society Field Conference Guidebook. 40: 191–211. Retrieved 30 October 2020.
  9. ^ a b c Dubiel, R.F. (1989). "Depositional and climatic setting of the Upper Triassic Chinle Formation, Colorado Plateau". In Lucas, S.G.; Hunt, A.P. (eds.). Dawn of the Age of Dinosaurs in the American Southwest. New Mexico Museum of Natural History. pp. 171–187. Retrieved 28 October 2021.
  10. ^ a b c Lucas, S.G. (1993). "The Chinle Group: revised stratigraphy and biochronology of Upper Triassic Nonmarine strata in the western United States". Museum of Northern Arizona Bulletin. 59: 27–50.
  11. ^ a b Lehman, T.M. (1994). "The saga of the Dockum Group and the case of the Texas/New Mexico boundary fault" (PDF). New Mexico Bureau of Mines & Mineral Resources Bulletin. 150: 37–51. Retrieved 1 September 2020.
  12. ^ a b c d e Cather, S.M.; Zeiger, Kate E.; Mack, Greg H.; Kelley, Shari A. (2013). "Toward standardization of Phanerozoic stratigraphic nomenclature in New Mexico". Rocky Mountain Geology. 48 (2): 101-124. CiteSeerX 10.1.1.667.3513. doi:10.2113/gsrocky.48.2.101. Retrieved 26 August 2020.
  13. ^ GEOLEX database bibliographic references for Chinle (viewed 19 March 2006)
  14. ^ a b c Woody, Daniel T. (2006). "Revised stratigraphy of the Lower Chinle Formation (Upper Triassic) of Petrified Forest National Park, Arizona" (PDF). In Parker, W.G.; Ash, S.R.; Irmis, R.B. (eds.). A century of research at Petrified Forest National Park : geology and paleontology. Museum of Northern Arizona. ISBN 0-89734-120-1. OCLC 71015548.
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  21. ^ "Shinarump Member of Chinle Formation". Colorado River Basin Stratigraphy. USGS. 6 May 2006. Retrieved 10 January 2011.
  22. ^ Milner, A.R. (2006). "Plant fossils from the Owl Rock or Church Rock Members, Chinle Formation, San Juan County, Utah". New Mexico Museum of Natural History and Science Bulletin. 37: 410–413. Retrieved 19 February 2022.
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  24. ^ a b c Lucas, S.G. (1991). "Triassic stratigraphy, paleontology and correlation, south-central New Mexico" (PDF). New Mexico Geological Society Field Conference Guidebook. 42: 243–253. Retrieved 6 August 2020.
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  27. ^ a b c Dubiel, R.F. (1989). "Sedimentology and revised nomenclature of the Upper Triassic Chinle Formation and the Lower Jurassic Wingate Sandstone, northwestern New Mexico and northeastern Arizona" (PDF). New Mexico Geological Society Field Conference Guidebook. 40: 213–223. Retrieved 12 November 2021.
  28. ^ Lucas, S.G.; Hunt, A.P. (1989). "Revised Triassic stratigraphy in the Tucumcari basin, east-central New Mexico". Dawn of the age of dinosaurs in the American southwest. New Mexico Museum of Natural History and Science. pp. 150–170. Retrieved 12 November 2021.
  29. ^ a b c Repenning, C.A.; Cooley, M.E.; Akers, J.P. (1969). "Stratigraphy of the Chinle and Moenkopi Formations, Navajo and Hopi Indian Reservations, Arizona, New Mexico, and Utah". U.S. Geological Survey Professional Paper. Professional Paper. 521-B: B1–B34. doi:10.3133/pp521B.
  30. ^ a b c d e Dubiel, R.F. (1987). "Sedimentology and new fossil occurrences of the Upper Triassic Chinle Formation, southeastern Utah". Four Corners Geological Society Field Conference Guidebook. 10: 99–107. Retrieved 12 November 2021.
  31. ^ O'Sullivan, R.B.; MacLachlan, M.E. (1975). "Triassic rocks of the Moab-White Canyon area, southeastern Utah". Four Corners Geological Society Field Conference Guidebook, 8th Field Conference (8): 129–141. Retrieved 12 November 2021.
  32. ^ Litwin, R.J., Traverse, A., and Ash, S.R., 1991. Preliminary palynological zonation of the Chinle Formation, southwestern U.S.A., and its correlation to the Newark Supergroup (eastern U.S.A.). Review of Paleobotany and Palynology, v. 77, pp. 269–287.
  33. ^ a b c d e Gehrels, George; Giesler, Dominique; Olsen, Paul; Kent, Dennis; Marsh, Adam; Parker, William; Rasmussen, Cornelia; Mundil, Roland; Irmis, Randall; Geissman, John; Lepre, Christopher (23 September 2020). "LA-ICPMS U–Pb geochronology of detrital zircon grains from the Coconino, Moenkopi, and Chinle formations in the Petrified Forest National Park (Arizona)". Geochronology. 2 (2): 257–282. doi:10.5194/gchron-2-257-2020.{{cite journal}}: CS1 maint: unflagged free DOI (link)
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  36. ^ a b c Rasmussen, Cornelia; Mundil, Roland; Irmis, Randall B.; Geisler, Dominique; Gehrels, George E.; Olsen, Paul E.; Kent, Dennis V.; Lepre, Christopher; Kinney, Sean T.; Geissman, John W.; Parker, William G. (20 July 2020). "U-Pb zircon geochronology and depositional age models for the Upper Triassic Chinle Formation (Petrified Forest National Park, Arizona, USA): Implications for Late Triassic paleoecological and paleoenvironmental change". GSA Bulletin. 133 (3–4): 539–558. doi:10.1130/B35485.1. ISSN 0016-7606.
  37. ^ Ogg, James G.; Huang, Chunju; Hinnov, Linda (May 2014). "Triassic timescale status: a brief overview" (PDF). Albertiana. 41: 3–30.
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  39. ^ Riggs, N.R.; Ash, S.R.; Barth, A.P.; Gehrels, G.E.; Wooden, J.L. (1 November 2003). "Isotopic age of the Black Forest Bed, Petrified Forest Member, Chinle Formation, Arizona: An example of dating a continental sandstone". GSA Bulletin. 115 (11): 1315–1323. doi:10.1130/B25254.1. ISSN 0016-7606.
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  43. ^ a b c Barnes, V.E., ed. (1983). "Tucumcari sheet". Geologic atlas of Texas. University of Texas-Austin, Bureau of Economic Geology.
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  45. ^ "Archived copy". Archived from the original on 1 April 2009. Retrieved 10 January 2011.{{cite web}}: CS1 maint: archived copy as title (link)

Further reading

  • Lucas, S.G. (1998). "Global Triassic tetrapod biostratigraphy and biochronology". Palaeogeography, Palaeoclimatology, and Palaeoecology, v. 143, pp. 347–384.

External links

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