Editing Morrison Formation

{{short description|Rock formation in the western United States}}
{{Infobox Rockunit
| name           = Morrison Formation
| image          = Green River UT 2005-10-14 2104.jpg
| caption        = The distinctive banding of the Morrison Formation, a group of rock layers that occur throughout [[Dinosaur National Monument]] and the source of fossils like those found at the Dinosaur Quarry
| type           = [[Geologic formation]]
| age            = [[Upper Jurassic]] ([[Kimmeridgian]] to [[Tithonian]]), {{fossilrange|156.3|146.8|earliest=158.3|latest=145.8}}
| period         = Upper Jurassic
| prilithology   = [[Mudstone]]
| otherlithology = [[Sandstone]], [[siltstone]], [[limestone]]
| namedfor       = [[Morrison, Colorado]]
| namedby        =
| region         = [[Arizona]], [[Colorado]], [[Idaho]], [[Kansas]], [[Montana]], [[Nebraska]], [[New Mexico]], [[North Dakota]], [[Oklahoma]], [[South Dakota]], [[Texas]], [[Utah]], [[Wyoming]]
| country        = [[United States]]<ref name=CGKN>{{cite web|title=Morrison Formation|url=http://cgkn1.cgkn.net/weblex/pdf/010000/GSCC00053010132.pdf|publisher=CGKN|access-date=25 May 2013}}{{dead link|date=February 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
| coordinates    = {{coord|39.651|N|105.188|W|display:inline}}
| unitof         =
| subunits       =
| underlies      = [[Cedar Mountain Formation]], [[Cloverly Formation]], [[Lakota Formation]], [[Burro Canyon Formation]]
| overlies       = [[Summerville Formation]], [[Beclabito Formation]], [[Curtis Formation]], [[Bell Ranch Formation]], [[Sundance Formation]]
| thickness      = Up to 200 m
| extent         =[[File:Stratotypes for members of the Morrison Formation.jpg|thumb|Stratotypes for members of the Morrison Formation]]
| area           =
| map            =
| map_caption    =
|paleocoordinates={{coord|40.4|N|53.2|W|display:inline}}}}
[[File:USGS Dakota Hogback Morrison 1926.jpg|thumb|Type locality for the Morrison Formation above the town of Morrison, Colorado.]]
The '''Morrison Formation''' is a distinctive sequence of [[Late Jurassic|Upper Jurassic]] [[sedimentary rock]] found in the western United States which has been the most fertile source of [[dinosaur]] [[fossil]]s in North America. It is composed of [[mudstone]], [[sandstone]], [[siltstone]], and [[limestone]] and is light gray, greenish gray, or red. Most of the fossils occur in the green siltstone beds and lower sandstones, relics of the rivers and floodplains of the [[Jurassic]] period.

It is centered in [[Wyoming]] and [[Colorado]], with outcrops in [[Montana]], [[North Dakota]], [[South Dakota]], [[Nebraska]], [[Kansas]], the panhandles of [[Oklahoma]] and [[Texas]], [[New Mexico]], [[Arizona]], [[Utah]], and [[Idaho]]. Equivalent rocks under different names are found in Canada.<ref name=PPT0404>{{cite journal |last=Parrish |first=J.T. |author2=Peterson, F. |author3= Turner, C.E. |year=2004 |title=Jurassic "savannah"-plant taphonomy and climate of the Morrison Formation (Upper Jurassic, Western USA) |journal=Sedimentary Geology |volume=167 |issue=3–4 |pages=137–162 |doi=10.1016/j.sedgeo.2004.01.004 |bibcode = 2004SedG..167..137P |url=http://doc.rero.ch/record/14574/files/PAL_E1788.pdf }}</ref> It covers an area of 1.5&nbsp;million square kilometers (600,000&nbsp;square miles), although only a tiny fraction is exposed and accessible to [[geologist]]s and [[Paleontology|paleontologists]]. Over 75% is still buried under the prairie to the east, and much of its western paleogeographic extent was eroded during [[Exhumation (geology)|exhumation]] of the [[Rocky Mountains]].

It was named after [[Morrison, Colorado]], where some of the first fossils in the formation were discovered by [[Arthur Lakes]] in 1877. That same year, it became the center of the [[Bone Wars]], a fossil-collecting rivalry between early paleontologists [[Othniel Charles Marsh]] and [[Edward Drinker Cope]]. In Colorado, New Mexico, and Utah, the Morrison Formation [[Uranium mining in the United States|was a major source]] of [[uranium]] ore.

== Geologic history ==
According to [[radiometric dating]], the Morrison Formation dates from 156.3&nbsp;±&nbsp;2&nbsp;million years old ([[Mega-annum|Ma]]) at its base,<ref name=TCR06>{{cite journal |last=Trujillo |first=K.C. |author2=Chamberlain, K.R. |author3= Strickland, A.  |year=2006 |title=Oxfordian U/Pb ages from SHRIMP analysis for the Upper Jurassic Morrison Formation of southeastern Wyoming with implications for biostratigraphic correlations |journal=Geological Society of America Abstracts with Programs |volume=38 |issue=6 |pages=7}}</ref> to 146.8&nbsp;±&nbsp;1&nbsp;million years old at the top,<ref name=SAB98>{{cite book |last=Bilbey |first=S.A. |year=1998 |chapter=Cleveland-Lloyd Dinosaur Quarry - age, stratigraphy and depositional environments |pages= 87–120 |title=The Morrison Formation: An Interdisciplinary Study |editor1=Carpenter, K. |editor2=Chure, D. |editor3=Kirkland, J.I. |series=Modern Geology |volume=22 |publisher=Taylor and Francis Group |issn=0026-7775}}</ref> which places it in the earliest [[Kimmeridgian]], and early [[Tithonian]] [[faunal stages|stages]] of the late Jurassic. This is similar in age to the [[Solnhofen limestone|Solnhofen Limestone]] Formation in Germany and the [[Tendaguru|Tendaguru Formation]] in [[Tanzania]]. The age and much of the fauna is similar to the [[Lourinhã Formation]] in Portugal.<ref>Mateus, O. 2006. Late Jurassic dinosaurs from the Morrison Formation, the Lourinhã and Alcobaça Formations (Portugal), and the Tendaguru Beds (Tanzania): a comparison. in Foster, J.R. and Lucas, S. G. R.M., eds., 2006, Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 36: 223-231.</ref> Throughout the western United States, it variously overlies the Middle Jurassic Summerville, [[Sundance Formation|Sundance]], Bell Ranch, Wanakah, and Stump Formations.

At the time, the supercontinent of [[Laurasia]] had recently split into the continents of North America and Eurasia, although they were still connected by land bridges. North America moved north and was passing through the [[subtropics|subtropical regions]].

The Morrison Basin, which stretched from New Mexico in the south to Alberta and Saskatchewan in the north, was formed during the [[Nevadan orogeny]], a precursor event to later orogenic episodes that created the Rocky Mountains started pushing up to the west. The deposits from their east-facing [[drainage basin]]s, carried by streams and [[river]]s from the Elko Highlands (along the borders of present-day Nevada and Utah) and deposited in [[swamp]]y lowlands, lakes, river channels and [[floodplain]]s, became the Morrison Formation.<ref name="turner-peterson-2004">{{cite journal |last1=Turner |first1=Christine E. |last2=Peterson |first2=Fred |title=Reconstruction of the Upper Jurassic Morrison Formation extinct ecosystem—a synthesis |journal=Sedimentary Geology |date=May 2004 |volume=167 |issue=3–4 |pages=309–355 |doi=10.1016/j.sedgeo.2004.01.009|bibcode=2004SedG..167..309T |url=http://doc.rero.ch/record/14577/files/PAL_E1793.pdf }}</ref>

In the north, the [[Sundance Sea]], an extension of the [[Arctic Ocean]], stretched through Canada down to the United States. [[Coal]] is found in the Morrison Formation of Montana, which means that the northern part of the formation, along the shores of the sea, was wet and swampy, with more vegetation.<!--more than what?--> [[Aeolian processes|Aeolian]], or wind-deposited sandstones, are found in the southwestern part, which indicates it was much more arid—a [[desert]], with sand [[dune]]s.

== Stratigraphy ==
[[File:Type SW-2.jpg|thumb|Type locality of the Salt Wash Member near White Wash, Grand County, Utah. The Morrison Formation is underlain by the brick-red Summerville Formation.]]
[[File:Morrison-Cedar Mountain Formations.jpg|thumb|The Jurassic-Cretaceous boundary is seen where the red and purple beds of the Morrison Formation abruptly contact the drab, gray bed of the overlying Cedar Mountain Formation. The contact is the K1 unconformity. Jessie's Twist, southwest of Green River City, Utah.]]
[[File:Brushy Basin Mbr, Morrison Fm.jpg|thumb|Brushy Basin Member showing the purple and red colors of paleosols (ancient soils). East side of the San Rafael Swell, Emery County, Utah.]]
[[File:Ralston Mbr.jpg|thumb|Gypsiferous facies of the Ralston Creek Member exposed in a road cut, Fremont County, Colorado.]]
The Morrison Formation is subdivided into several members, the occurrence of which are varied across the geographic extent of the Morrison. Members are (in alphabetical order):<ref name="USGS Geolex: Morrison Formation">{{Cite web|title=Geologic Unit: Morrison|url=https://ngmdb.usgs.gov/Geolex/Units/Morrison_9394.html|access-date=December 30, 2020|website=USGS Geolex}} </ref><ref>{{Cite web|title=Geologic Unit: Windy Hill|url=https://ngmdb.usgs.gov/Geolex/Units/WindyHill_11198.html|access-date=December 30, 2020|website=USGS Geolex}} </ref>
*[[Bluff Formation|Bluff Sandstone Member]] (AZ, CO, NM, UT): Well-sorted, light brown to white sandstone with large grains and components of chert. Interpreted as being deposited in an aeolian setting, at the edge of a dune field.<ref>{{cite web |last1=Condon |first1=S.M. |title=Stratigraphic Sections of the Middle Jurassic Wanakah Formation, Cow Springs Sandstone, and adjacent rocks, from Bluff, Utah, to Lupton, Arizona: U.S. Geologic Survey Oil and Gas Investigation Chart, OC-131 |url=https://ngmdb.usgs.gov/Prodesc/proddesc_5160.htm |website=USGS Geolex |publisher=U.S. Geological Survey |access-date=December 31, 2020}}</ref>
[[File:Saltwash Tidwell.JPG|thumb|

Reddish mudstones of the Tidwell Member underlying the whitish sandstones of the Saltwash Member, south of Cisco, Utah.

]] [[File:BrushyBasin.jpg|thumb|

Brushy Basin Member on the Colorado Plateau

]]
*Brushy Basin Member (AZ, CO, NM, UT): conglomerate interbedded with mudstone; up to fifty percent by volume is made up of altered vitric ash, which originated as felsic ash falls. Deposition likely occurred in a fluvial-lacustrine environment, with the lacustrine component tending towards [[Dry lake|playas]].<ref> Bell, Thomas, "Deposition and Diagenesis of the Brushy Basin Member and the Upper Part of the Westwater Canyon Member of the Morrison Formation, San Juan Basin, New Mexico," in ''A Basin Analysis Case Study: The Morrison Grants Uranium Region New Mexico'', edited by Neil S. Fishermen, Elmer S. Santos, and Christine E. Turner-Peterson, American Association of Petroleum Geolgists, Tulsa, 1986. </ref>
*Fiftymile Member (UT): Mainly present in the Kaiparowits basin, consisting of interbedded sandstone and mudstone, with minimal conglomerate. Locally, it is the uppermost member and has contact with the [[Dakota Formation]].<ref>{{cite journal |last1=Peterson |first1=Fred |title=Revisions to Stratigraphic Nomenclature of Jurassic and Cretaceous Rocks of the Colorado Plateau |journal=U.S. Geological Survey Bulletin |date=1988 |volume=1633 |issue=B |page=13-56 |url=https://pubs.usgs.gov/bul/1633a-c/report.pdf |access-date=December 31, 2020}}</ref>
*Jackpile Sandstone Member (NM): primarily a whitish crossbedded subarkose sandstone with a clay matrix. It is interbedded with variegated, pale-green to red, bentonitic mudstone lenses.<ref name="owen-etal-1984">{{cite journal |last1=Owen |first1=Donald E. |last2=Walters | first2=Lester J. Jr. |last3=Beck |first3=Ronald G. |title=The Jackpile Sandstone Member of the Morrison Formation in west-central New Mexicoby Donald E. jwen, Consulting Geologist, Tulsa, 0K 74152, and Lester J.Walters, Jr. and Ronald G. Beck, ARCO Oil and Gas Co., Dallas, IX75221 a formal definiti |journal=New Mexico Geology |date=August 1984 |volume=6 |issue=3 |doi=10.58799/NMG-v6n3.45 |url=https://geoinfo.nmt.edu/publications/periodicals/nmg/6/n3/nmg_v6_n3_p45.pdf |access-date=4 June 2020}}</ref> However, recent [[detrital zircon geochronology]] results have suggested that the Jackpile Sandstone Member is part of the [[Burro Canyon Formation]].<ref>{{cite journal |last1=Dickinson |first1=William R. |last2=Gehrels |first2=George E. |title=Implications of U-Pb ages of detrital zircons in Mesozoic strata of the Four Corners region for provenance relations in space and time |journal=New Mexico Geological Society Field Conference Series |date=2010 |volume=61 |pages=135–146 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/61/61_p0135_p0146.pdf |access-date=27 October 2020}}</ref><ref>{{cite journal |last1=Cather |first1=Steven M. |title=Jurassic stratigraphic nomenclature for northwestern New Mexico |journal=New Mexico Geological Society Special Publication |date=2020 |volume=14 |pages=145–151 |url=https://nmgs.nmt.edu/publications/special/14/NMGS_SP-14.pdf |access-date=31 October 2020}}</ref>
*Ralston Creek Member (CO): formerly a considered separate formation and recently reclassified as the basal member of the Morrison in eastern Colorado. It appears analogous to the Tidwell and Salt Wash Members. This reclassification is supported by more detailed examination of the contacts and radiometric dating. The Ralston Creek contains conglomerate, sandstone, gypsum-mudstone, and gypsum-sandstone-mudstone facies; it is undetermined if the gypsum is of marine or lacustrine origin.<ref>{{Cite journal|last1=Carpenter|first1=Kenneth|last2=Lindsey|first2=Eugene|date=2019-01-31|title=Redefining the Upper Jurassic Morrison Formation in Garden Park National Natural Landmark and vicinity, eastern Colorado|url=https://giw.utahgeology.org/giw/index.php/GIW/article/view/37|journal=Geology of the Intermountain West|language=en|volume=6|pages=1–30|doi=10.31711/giw.v6.pp1-30|issn=2380-7601|doi-access=free}}</ref> 
*Recapture Member (AZ, CO, NM, UT): forms the bottom of the Morrison across most of its range, overlying the [[Entrada Sandstone|Entrada]] and [[Wanakah Formation|Wanakah]] Formations.<ref>{{cite journal |last1=Condon |first1=S.M. |last2=Huffman |first2=A.C. |title=Revisions in nomenclature of the Middle Jurassic Wanakah Formation, Northwest New Mexico and northeast Arizona |journal=U.S. Geological Survey Bulletin |date=1988 |volume=1633 |issue=A |page=1-12 |url=https://ngmdb.usgs.gov/Prodesc/proddesc_92777.htm |access-date=8 February 2021}}</ref> Consists of clayey sandstone and [[Mudstone|claystone]], representing a fluvial setting, interbedded with purely aeolian sandstone facies;<ref name="Kirk-Condon-in-BACS-1989">{{cite book |author1=Allan R. Kirk |author2=Steven M. Condon |chapter= Structural Control of Sedimentation Patterns and the Distribution of Uranium Deposits in the Westwater Canyon Member of the Morrison Formation, Northwestern New Mexico--A Subsurface Study |editor1-last=Turner-Peterson |editor1-first=C.E. |editor2-last=Santos |editor2-first=Elmer S. |editor3-last=Fishman |editor3-first=Neil S. |title=Basin Analysis Case Study: The Morrison Formation, Grants Uranium Region, New Mexico |date=1986 |publisher=The American Association of Petroleum Geologists |location=Tulsa |page=110-111}}</ref> in places, it also contains a large (up to nineteen percent) of [[orthoclase]] feldspar inclusions.<ref>{{cite journal |last1=Peterson |first1=Fred |last2=Turner-Peterson |first2=C.E. |title=The Morrison Formation of the Colorado Plateau: recent advances in sedimentology, stratigraphy, and paleotectonics |journal=Hunter |date=1987 |volume=2 |issue=1 |page=1-18 |url=https://ngmdb.usgs.gov/Prodesc/proddesc_91414.htm |access-date=8 February 2021}}</ref>
*Salt Wash Member (CO, UT): composed of fluvial sandstone,<ref name="Kirk-Condon-in-BACS-1989"> </ref> with occasional [[Conglomerate (geology)|conglomeratic]] tendencies.<ref name="O'Sullivan-1984">{{cite journal |last1=O'Sullivan |first1=R.B. |title=The base of the Upper Jurassic Morrison Formation in east-central Utah |journal=U.S. Geological Survey Bulletin |date=1984 |volume=1561 |page=17 |url=https://ngmdb.usgs.gov/Prodesc/proddesc_92737.htm |access-date=8 February 2021}}</ref>
[[File:Tidwell-Peterson stratotype.jpg|thumb|Tidwell Member at the type section, Shadscale Mesa, Emery County, Utah.]]
*{{anchor|Tidwell Member}}'''Tidwell Member''' (AZ, CO, NM, UT): in the northern part of the [[Colorado Plateau]], it is the basal member of the Morrison. Mainly composed of siltstone, shale, and sandstone, and occasionally incorporates limestone [[clasts]], along with thin beds of limestone.<ref name="O'Sullivan-1984"></ref> Depositional environments range from mudflats to fluvial, to evaporate and [[lacustrine]]. The Morrison as a whole resembles the Tidwell.<ref name="Peterson-1988">{{cite journal |last1=Peterson |first1=Fred |title=Stratigraphy and Nomenclature of Middle and Upper Jurassic rocks, western Colorado Plateau, Utah and Arizona |journal=U.S. Geological Survey Bulletin |date=1988 |volume=1633 |issue=B |page=13-56 |url=https://ngmdb.usgs.gov/Prodesc/proddesc_92778.htm |access-date=9 February 2021}}</ref>
*Unkpapa Sandstone Member (SD): occurs primarily in western South Dakota as a well-sorted, fine-grained sandstone, consisting primarily of quartz, with some feldspar inclusions.<ref name="Mapel-Chisholm-1962">{{cite journal |last1=Mapel |first1=W.J. |last2=Chisholm |first2=W.A. |title=Nonopaque heavy minerals in sandstone of Jurassic and Cretaceous age in the Black Hills, Wyoming and South Dakota |journal=U.S. Geological Survey Bulletin |date=1962 |volume=1161 |issue=C |page=1-59}}</ref> Locally overlain by the [[Lakota Formation]] or the main body of the Morrison, and overlies the Redwater Shale Member of the [[Sundance Formation]].<ref>{{cite book |author1=Szigeti, G.J |author2=Fox, J.E. |chapter=Unkpapa Sandstone (Jurassic), Black Hills, South Dakota; an eolian facies of the Morrison Formation |editor1-last=Ethridge |editor1-first=F.G. |editor2-last=Flores |editor2-first=R.M. |title=Recent and Ancient non marine depositional environments: models for exploration |date=1979 |publisher=Society of Economic Paleontologists and Mineralogists Special Publication |location=Casper, WY |page=331-349}}</ref> Occasionally referred to as a separate formation, chiefly within the [[Black Hills]] region.<ref name="Mapel-Chisholm-1962">{{cite journal |last1=Mapel |first1=W.J. |last2=Chisholm |first2=W.A. |title=Nonopaque heavy minerals in sandstone of Jurassic and Cretaceous age in the Black Hills, Wyoming and South Dakota |journal=U.S. Geological Survey Bulletin |date=1962 |volume=1161 |issue=C |page=1-59}}</ref>
*Westwater Canyon Member (AZ, CO, NM, UT): consists of sandstone interbedded with mudstone lenses and the occasional conglomerate component. Deposited in a braided-stream environment, high in organic matter. The term "Poison Canyon Sandstone" is informally applied to the upper sandstone sections of the member.<ref name="Kirk-Condon-in-BACS-1989"> </ref> The Westwater Canyon Member is the main source of uranium ore in the Morrison, especially in the [[San Juan Basin]].<ref name="Turner-Peterson-in-BACS-1989">{{cite book |author1=Christine E. Turner-Peterson |chapter=Fluvial Sedimentology of a Major Uranium-Bearing Sandstone-- A Study of the Westwater Canyon Member of the Morrison Formation, San Juan Basin, New Mexico |editor1-last=Turner-Peterson |editor1-first=C.E. |editor2-last=Santos |editor2-first=Elmer S. |editor3-last=Fishman |editor3-first=Neil S. |title=Basin Analysis Case Study: The Morrison Formation, Grants Uranium Region, New Mexico |date=1986 |publisher=The American Association of Petroleum Geologists |location=Tulsa |page=110-111}}</ref>
*Windy Hill Member (CO, SD, UT, WY): Formerly included as the upper member of the Sundance Formation, as, like the rest of the Sundance, it was deposited in marine settings; however, it is separated by an [[unconformity]] and interfingers with the Morrison, meriting the nomenclature shift.<ref>{{cite book |author1=Fred Peterson |chapter=Sand dunes, sabkhas, streams, and shallow seas: Jurassic paleogeography in the southern part of the Western Interior Basin |editor1-last=Caputo |editor1-first=M.V. |editor2-last=Peterson |editor2-first=J.A. |editor3-last=Franczyk |editor3-first=K.J. |title=Mesozoic Systems of the Rocky Mountain Region, USA |publisher=Society of Economic Paleontologists and Mineralogists, Rocky Mountain Section |page=233-272}}</ref> Composed of limey, fossiliferous sandstone, generally interpreted to be deposited in a marine setting.<ref name="Pipiringos-1968">{{cite journal |last1=Pipiringos |first1=G.N. |title=Correlation and Nomenclature of some Triassic and Jurassic Rocks in south-central Wyoming |journal=U.S. Geological Survey Professional Paper |date=1968 |volume=594 |issue=D |page=1-26 |url=https://ngmdb.usgs.gov/Prodesc/proddesc_92909.htm |access-date=8 February 2021}}</ref>
[[Image:Popcorn Texture.JPG|thumb|"Popcorn" texture due to [[bentonite]], formed from volcanic ash, characterizes the Brushy Basin Member]]

Other informal or disused designations of the Morrison include the Stockett Bed in Montana, an unofficial sub-unit which contains bituminous coal;<ref>{{cite journal |last1=Daniel |first1=J.A. |last2=Bartholomew |first2=M.J. |last3=Murray |first3=R.C. |title=Geological Characteristics of the Stockett Bed Coal in the Central Great Falls Coal Field, Montana |journal=Montana Bureau of Mines and Geology Special Publication |date=1992 |volume=102 |page=145-157}}</ref> the outdated terms Casamero, Chavez, and Prewitt Sandstone for the Brushy Basin, Recapture, and Westwater Canyon, respectively;<ref name="smith-1954">{{cite journal |last1=Smith |first1=C.T. |title=Geology of the Thoreau quadrangle, McKinley and Valencia Counties, New Mexico |journal=New Mexico Bureau of Mines and Mineral Resources |date=1954 |volume=31}}</ref><ref name="Robertston-1990">{{cite journal |last1=Robertson |first1=J.F. |title=Geologic map of the Thoreau quadrangle, McKinley County, New Mexico |journal=U.S. Geological Survey |date=1990}}</ref> and the Bullington Member, which has been discarded entirely.

== Fossil content ==
{{main|Paleobiota of the Morrison Formation}}[[File:Morrison Formation near Arches.jpg|thumb|Bluish beds of the Brushy Basin Member containing alkali minerals deposited in Lake T'oo'dichi']]
{{main|List of dinosaurs of the Morrison Formation}}
Though many of the Morrison Formation fossils are fragmentary, they are sufficient to provide a good picture of the flora and fauna in the Morrison Basin during the Kimmeridgian. Overall, the [[paleoclimate|climate]] was dry, similar to a [[savanna]] but, since there were no [[angiosperm]]s ([[grass]]es, [[flower]]s, and some [[trees]]), the flora was quite different. [[Conifers]], the dominant plants of the time, were to be found with [[ginkgo]]s, [[cycad]]s, [[tree fern]]s, and [[Equisetum|horsetail rushes]]. Much of the fossilized vegetation was [[riparian]], living along the river flood plains. Along the rivers, there were [[fish]], [[frog]]s, [[salamander]]s, [[lizard]]s, [[crocodile]]s, [[turtle]]s, [[pterosaur]]s, [[crayfish]], [[clam]]s, and [[mammaliforms]].
[[File:Belt coal seam.jpg|thumb|Coal seam in the Morrison Formation, Belt, Montana]]
The [[dinosaur]]s were most likely riparian, as well.<ref name="turner-peterson-2004"/> Hundreds of dinosaur fossils have been discovered, such as ''[[Allosaurus]]'', ''[[Ceratosaurus]]'', ''[[Torvosaurus]]'', ''[[Camptosaurus]]'', ''[[Ornitholestes]]'', several [[Stegosauria|stegosaurs]] comprising at least two species of ''[[Stegosaurus]]'' and the slightly older ''[[Hesperosaurus]]'', and the early [[Ankylosauria|ankylosaurs]], ''[[Mymoorapelta]]'' and ''[[Gargoyleosaurus]]'', most notably a very broad range of [[sauropod]]s (the giants of the [[Mesozoic]] era).<ref>{{Cite journal|last1=Dodson|first1=Peter|last2=Behrensmeyer|first2=A. K.|last3=Bakker|first3=Robert T.|last4=McIntosh|first4=John S.|date=1980|title=Taphonomy and Paleoecology of the Dinosaur Beds of the Jurassic Morrison Formation|url=http://dx.doi.org/10.1017/s009483730000676x|journal=Paleobiology|volume=6|issue=2|pages=208–232|doi=10.1017/s009483730000676x|bibcode=1980Pbio....6..208D |s2cid=130686856 |issn=0094-8373|url-access=subscription}}</ref> Since at least some of these species are known to have nested in the area (''Camptosaurus'' [[embryo]]es have been discovered), there are indications that it was a good [[natural environment|environment]] for dinosaurs and not just home to migratory, seasonal populations. However, the large body mass of the sauropods has been interpreted as an adaptation to migration in times of drought.<ref name="turner-peterson-2004"/>

Sauropods that have been discovered include ''[[Diplodocus]]'' (most famously, the first nearly complete specimen of ''D. carnegii'', which is now exhibited at the [[Carnegie Museum of Natural History]], in Pittsburgh, Pennsylvania), ''[[Camarasaurus]]'' (the most commonly found sauropod), ''[[Brachiosaurus]]'', ''[[Apatosaurus]]'', ''[[Brontosaurus]]'', ''[[Barosaurus]]'', the uncommon ''[[Haplocanthosaurus]]'' and ''[[Supersaurus]]''. The very diversity of the sauropods has raised some questions about how they could all co-exist. While their body shapes are very similar (long neck, long tail, huge elephant-like body), they are assumed to have had very different feeding strategies, in order for all to have existed in the same time frame and similar environment.

=== Sites and quarries ===
[[File:Dinosaur National Monument-inside the Dinosaur Quarry building.jpeg|thumb|right|250px|Workers inside the Dinosaur Quarry building, at the [[Dinosaur National Monument]]]]
Locations where significant Morrison Formation fossil discoveries have been made include:

==== Colorado ====
[[File:FruitaPaleo.JPG|thumb|250px|Fruita Paleontological Resource Area. One of the sites is denoted by the arrow.]]
* [[Garden Park, Colorado]]: One of the three major sites excavated by the paleontologists [[Othniel Charles Marsh]] and [[Edward Drinker Cope]] during the Bone Wars in 1877, though most of the specimens were too incomplete to classify (''nomina dubia'') during the 1877-78 field seasons. The first nearly complete skeletons of ''[[Stegosaurus]], [[Ceratosaurus]],'' and ''[[Allosaurus]]'' were discovered at the site, including the type specimens of the former two and the proposed neotype of ''Allosaurus fragilis,'' in the 1883-1886 Yale field seasons.<ref>Evanoff, E., & Carpenter, K. (1998). [https://www.researchgate.net/profile/Kenneth-Carpenter-2/publication/40662156_History_sedimentology_and_taphonomy_of_Felch_Quarry_1_and_associated_sandbodies_Morrison_Formation_Garden_Park_Colorado/links/5c61c77a45851582c3e16a11/History-sedimentology-and-taphonomy-of-Felch-Quarry-1-and-associated-sandbodies-Morrison-Formation-Garden-Park-Colorado.pdf History, sedimentology, and taphonomy of felch quarry 1 and associated sandbodies, Morrison Formation, Garden Park, Colorado.] ''Modern Geology'', ''22'', 423-170.</ref>  In 1992, a specimen of ''Stegosaurus stenops'' was discovered with its [[Armour (zoology)|armor]] still in place, which confirmed that the dinosaur had two rows of plates on its back.
* [[Dry Mesa Quarry]], Colorado: A wide variety of fauna, as well as the most diverse set of dinosaurs from any Morrison Formation quarry. The first dig was in 1972, by researchers from [[Brigham Young University]]. Unique specimens include the longest dinosaur known, ''[[Supersaurus]]'', the [[wikt:chimera|chimeric]] ''[[Ultrasauros]]'', and the largest [[carnivore]] on the continent, ''[[Torvosaurus]]''.
* Fruita Paleontological Resource Area: Badlands sites located south of [[Fruita, Colorado|Fruita]], were actively worked by George Callison from California State University and the Los Angeles County Museum of Natural History. Numerous specimens of mammals, lizards, and crocodiles were found. Most recently, ''[[Fruitafossor windscheffelia]]'' and the new dinosaur ''[[Fruitadens]]'' were described from the area.
* [[Purgatoire River track site]], [[Otero County, Colorado|Otero County]].

==== Utah ====
* [[Cleveland-Lloyd Dinosaur Quarry]], Utah: First excavated by geologists from the University of Utah in the late 1920s. [[William Lee Stokes]] led an expedition from Princeton in 1939. During the Jurassic, the quarry was likely an ephemeral pond, where dinosaurs gathered and died due to severe drought.<ref>{{cite web |last1=Gates |first1=Terry |title=The Late Jurassic Cleveland-Lloyd Dinosaur Quarry as a Drought-Induced Assemblage |url=https://pubs.geoscienceworld.org/sepm/palaios/article-abstract/20/4/363/100047/The-Late-Jurassic-Cleveland-Lloyd-Dinosaur-Quarry |publisher=PALAIOS |access-date=19 June 2024}}</ref> Their bodies were reworked by seasonal flooding events, which also added other partial carcasses from elsewhere.<ref>{{cite journal |last1=Peterson |first1=Joseph E. |last2=Warnock |first2=Jonathan P. |last3=Eberhart |first3=Shawn L. |last4=Clawson |first4=Steven R. |last5=Noto |first5=Christopher R. |title=New data towards the development of a comprehensive taphonomic framework for the Late Jurassic Cleveland-Lloyd Dinosaur Quarry, Central Utah |journal=PeerJ |pages=e3368 |doi=10.7717/peerj.3368 |date=2017|volume=5 |doi-access=free |pmid=28603668 |pmc=5463971 }}</ref> ''[[Allosaurus fragilis]]'' is by far the most common dinosaur at this site, making it a model organism for studies of paleobiology in basal theropods. The rare theropods ''[[Stokesosaurus]]'' and ''[[Marshosaurus]]'' specimens were also first discovered here.
* [[Dinosaur National Monument]], Utah: First excavated by Earl Douglas working for the [[Carnegie Museum of Natural History|Carnegie Museum]] in 1909 with the purpose of finding sauropods from the Morrison Formation for public display. Monument also has fossilized dinosaurs from the [[Cedar Mountain Formation]]. 
* [[Hanksville-Burpee Quarry]], [[Hanksville, Utah|Hanksville]]

==== Wyoming ====
* [[Bone Cabin Quarry]], Wyoming
* [[Como Bluff]], Wyoming: One of the most renowned fossil sites in North America. It was first worked by Cope and particularly Marsh in 1877 and has been the source of many different sauropods and non-dinosaur species. The [[Cloverly Formation]] from the Cretaceous and some [[Triassic]] strata are also exposed at this location.
* The [[Wyoming Dinosaur Center]], [[Thermopolis, Wyoming|Thermopolis]]
* [[Ten Sleep]], including Dana Quarry from where at least 12 sauropods and theropods are recovered.<ref>Saleiro, A., & Mateus O. (2017).  Upper Jurassic bonebeds around Ten Sleep, Wyoming, USA: overview and stratigraphy. Abstract book of the XV Encuentro de Jóvenes Investigadores en Paleontología/XV Encontro de Jovens Investigadores em Paleontologia, Lisboa, 428 pp.. 357-361.</ref>

==Economic geology==
The Morrison Formation contains [[uranium]] deposits, including the Jackpile uranium body discovered near [[Grants, New Mexico]] in 1951.<ref name="owen-etal-1984"/> The ore deposits in the rich Grants mineral belt are concentrated in sandstone beds of the Westwater Canyon Member and the Jackpile Member. Mines in this belt produced {{convert|340000000|lbs|kg|sp=us}} of [[Triuranium octoxide|U<sub>3</sub>O<sub>8</sub>]] between 1948 and 2002. The uranium was precipitated by plant debris and [[Humic substance|humate]] that acted as reducing agents.<ref>{{cite journal |last1=Wilton |first1=Ted |last2=Chavez | first2=William X. Jr. |last3=Caldwell |first3=Samantha |title=Sandstone-hosted uranium deposits at the Cebolleta Land Grant, Cibola County, New Mexico |journal=New Mexico Geological Society Special Publication |date=2020 |volume=14 |pages=67–75 |url=https://nmgs.nmt.edu/publications/special/14/NMGS_SP-14.pdf |access-date=27 October 2020}}</ref>

== See also ==
{{Portal|Dinosaurs|Paleontology}}
* [[Chugwater Formation]]
* [[Lists of dinosaur-bearing stratigraphic units]]
* [[List of fossil sites]] ''(with link directory)''
* [[List of Paleobiota of the Morrison Formation]]
* [[Uranium mining and the Navajo people]]

==Citations==
{{reflist}}

== Further reading ==
{{colbegin|colwidth=30em}}
* Foster, J. 2007. Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. 389pp.
* Foster, J.R. 2003. Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. Bulletin 23.
* Jenkins, J.T. and J.L. Jenkins. 1993. Colorado's Dinosaurs. Denver, Colorado: Colorado Geologic Survey. Special Publication 35.
* Mateus, O. 2006. Late Jurassic dinosaurs from the Morrison Formation, the Lourinhã and Alcobaça Formations (Portugal), and the Tendaguru Beds (Tanzania): a comparison. in Foster, J.R. and Lucas, S. G. R.M., eds., 2006, Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 36: 223-231.
{{colend|colwidth=30em}}

== External links ==
{{Commons category|Morrison Formation}}
* [http://www.mnhm.org/ Morrison Natural History Museum] home page.
* ''[https://web.archive.org/web/20050501220306/http://rainbow.ldgo.columbia.edu/courses/v1001/morisson14.html Dinosaurs and the History of Life]'', Columbia University lecture on the Morrison Formation.
* [https://web.archive.org/web/20060615094030/http://www.nps.gov/dino/morrison.htm Geology of the (Dinosaur National Monument) Quarry], from the National Park Service.
* [https://web.archive.org/web/20110720115730/http://macrostrat.geology.wisc.edu/unit_info.php?name_id=1351 Spatial distribution of Morrison in Macrostrat].
* [https://paleodb.org/cgi-bin/bridge.pl?action=displayCollectionDetails&collection_no=13275 Paleobiology Database: Dalton Well Dinosaur Track Site (Morrison Formation): Late/Upper Jurassic, Utah]
* [https://paleodb.org/cgi-bin/bridge.pl?action=displayCollectionDetails&collection_no=13277 Paleobiology Database: Black Ridge Dinosaur Track Site (Morrison Formation): Late/Upper Jurassic, Colorado]
* [https://web.archive.org/web/20070208065858/http://home.arcor.de/ktdykes/dryolest.htm Catalogue of Morrison mammals (bottom of the page)]
* [https://www.nps.gov/dino/learn/nature/morrison-formation.htm NPS.gov: "About the Morrison Formation in Dinosaur National Monument'']
* [https://www.britannica.com/place/Morrison-Formation Britannica.com: Morrison Formation geology]

{{Chronostratigraphy of Colorado|Mesozoic state=expanded}}

[[Category:Morrison Formation| ]]
[[Category:Geologic formations of the United States]]
[[Category:Jurassic System of North America]]
[[Category:Late Jurassic North America]]
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[[Category:Kimmeridgian Stage]]
[[Category:Tithonian Stage]]
[[Category:Mudstone formations]]
[[Category:Siltstone formations]]
[[Category:Limestone formations of the United States]]
[[Category:Sandstone formations of the United States]]
[[Category:Fluvial deposits]]
[[Category:Shallow marine deposits]]
[[Category:Jurassic fossil record]]
[[Category:Fossiliferous stratigraphic units of North America]]
[[Category:Jurassic paleontological sites of North America]]
[[Category:Jurassic Arizona]]
[[Category:Jurassic Colorado]]
[[Category:Jurassic Idaho]]
[[Category:Jurassic Kansas]]
[[Category:Jurassic Montana]]
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[[Category:Jurassic formations of New Mexico]]
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[[Category:Jurassic geology of Utah]]
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